bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen Evolution Behavior of Ni-Containing Alloy Electrodes in NaOH–KOH Hydrate Melt
Authors: Kawaguchi Kenji , Nohira Toshiyuki
Published: December 2024

Hydrogen is expected to be the next-generation energy carrier with zero CO2 emissions. Alkaline water electrolysis (AWE) is one of the methods for hydrogen production; however, improving its energy efficiency is a challenge. We are currently developing a highly efficient water electrolysis using hydroxide hydrate melts at 150–200°C [1,2]. Recently, we reported that the overpotential for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a Ni electrode in a NaOH–KOH hydrate melt at 200°C under atmospheric pressure was significantly reduced compared to a 30 wt% KOH aqueous solution at 80°C, which is a typical electrolyte for conventional commercial AWE [2]. In addition, the OER overpotential was found to be larger than the HER overpotential at the Ni electrode in the NaOH–KOH hydrate melt [2]. In the present study, we investigated the OER behavior of Ni-containing alloys in the NaOH–KOH hydrate melt.

Linear sweep voltammetry was performed in the NaOH–KOH hydrate melt (NaOH:KOH:H2O = 9:61:30 mol%) at 150 and 200°C using a three-electrode cell. Several types of commercially available Ni-containing alloy plates with a flag-shaped and 3 mm diameter were used as the working electrode. A Ni rod was used as the counter electrode. A palladium hydride (Pd–H) electrode was used as the reference electrode and the potential was calibrated with respect to the reversible hydrogen electrode (RHE). All measured potentials were IR compensated. All measurements were performed in stationary electrolytes under Ar gas flow at atmospheric pressure.

Figure 1 shows anodic polarization curves at Ni–Fe and Ni–Cu alloy electrodes in the NaOH–KOH hydrate melt at 150°C. The polarization of Ni–Fe and Ni–Cu alloy electrodes is lower than that of the Ni electrode. In this paper, we will also present the results for other Ni-containing alloys.

A part of this study was supported by Adaptable and Seamless Technology transfer Program through Target-driven R&D (A-STEP) from Japan Science and Technology Agency (JST) Grant Number JPMJTR23TB.

[1] K. Kawaguchi, K. Goto, A. Konno, and T. Nohira, J. Electrochem. Soc., 170, 084507 (2023).

[2] K. Goto, K. Kawaguchi, and T. Nohira, Electrochemistry, 92, 043021 (2024).

Figure 1
Low-Temperature Molten Salt Electrochemical CO2upcycling for Advanced Energy Materials
Authors: Prasad Thapaliya Bishnu , Dai Sheng , Mahurin Shannon
Published: December 2024

CO2 upcycling into advanced energy materials represents a promising approach for mitigating the climate crisis stemming from CO2 emissions. In this study, we present a novel method involving molten salt CO2 upcycling to generate value-added materials, including graphene, graphite, microporous carbon, and transition metal oxide encapsulated graphite, with precise control over microstructure at a moderate temperature of 450°C. By carefully adjusting electrochemical parameters such as voltage, temperature, and cathode material, we successfully converted CO2 into various structural architectures, such as graphene and graphite, exhibiting customizable morphology and porosity at this relatively low temperature. The resulting electro-reduced carbon materials displayed impressive characteristics including high specific capacity, stable cycling performances, and exceptional rate capability when employed as anode materials in lithium-ion/sodium-ion batteries (LIBs/SIBs). Our innovative approach demonstrates efficient CO2 upcycling into diverse carbon architectures tailored for improved energy storage, thereby contributing to the advancement of clean and sustainable energy technologies by curbing carbon emissions towards achieving sustainable energy objectives.
Study on Ionic Plastic Crystals As Lithium-Ion Electrolytes
Authors: Sugisawa Hiroki , Takahashi Toshifumi , Nakatsuka Emi , Aikyo Hiroyuki , Fukii Kaoru , Kato Masahiko , Satake Kenichi , Hamamura Tomofumi
Published: December 2024

Ionic plastic crystals (IPC) have a highly symmetrical crystal structure similar to CsCl or NaCl, as a result of utilizing the energy associated with crystal melting for molecular rotational motion [1,2]. The introduction of lithium salt into these materials can realize the lithium-ion electrolytes enhanced conductivity compared to pure plastic crystals [3]. However, this operation concurrently reduces the plastic crystal's melting point, thereby limiting the temperature range existing as an electrolyte [3]. Therefore, this study explores two avenues to discover materials featuring the plastic crystal phase with the broad temperature range and the high ion conductivity.

In the first approach, attention is directed towards the anion structure of lithium salts. Conventionally, the anion of lithium salts is selected to be same with one of the plastic crystals. However, investigating various combinations of plastic crystals and lithium salts holds promise. The second approach is development of additives. Increasing the amount of additives similar to lithium salts causes the disadvantage of narrowing the temperature range of the plastic crystal phase. Therefore, we seek to investigate if this disadvantage can be avoided through anion or additive modification. Detailed findings from these investigations will be reported on the day of the presentation.

[1] J. Pringle, Phys. Chem. Chem. Phys.
15, 1339 (2013).

[2] J. Pringle, P.C. Howlett, D.R. MacFarlanea and M. Forsyth, J. Mater. Chem.
20, 2056 (2010).

[3] M.L. Thomas, K. Hatakeyama-Sato, S. Nanbu, and M. Yoshizawa-Fujita, Energy Adv.
2, 748 (2023).
Online Monitoring of Alkali Chloride Molten Salt Composition, Speciation, and Basicity Using UV-Vis-NIR Absorption Spectroscopy
Authors: Moon Jeremy , Sharpless Laurel , Chidambaram Dev
Published: December 2024

For molten salt reactors and pyrochemical reprocessing systems, it is vital to monitor the concentration and speciation of U and fission products in the fuel salt as well as the basicity of the salt. We show that NIR spectroscopy allows for better monitoring of actinide and lanthanide fission product concentrations and speciation with greater sensitivity than UV and visible range absorption spectroscopy due to fewer interfering absorption lines, more tractable molar absorption coefficients of transitions present in this range, and less sensitivity to scattering from solid phases suspended in the salt. Additionally, to monitor the basicity of the molten salt mixture, we have explored the use of Pb2+ and Bi2+ as probe ions; shifts in the absorption maxima of their 6s→6p electronic transition are correlated to changes in the Lewis basicity of the molten salt. We show that this optical basicity method is viable in alkali chloride molten salts and may be of use for online monitoring of molten salt chemistry in nuclear molten salt applications.

This work was funded by Department of Energy under award DE-EE0009822
Synthesis and Characterization of Novel Polymerizable Boronium Ionic Liquids
Authors: Durkin David P. , Stachurski Christopher D. , Cho Whirang , Kinnaman Conner M. , Larm Nathaniel E. , Davis James H. , Trulove Paul C.
Published: December 2024

Boronium ionic liquids (BILs) are an emergent class of zwitterionic materials that have great potential as electrolytes for electrochemical energy storage. Their high electrochemical stability, afforded by charge delocalization across the cation, and thermal stability make them attractive electrolytes for supercapacitors. In this work, a series of novel polymerizable BIL (polyBIL) cations were paired with bis(trifluoromethane)sulfonimide, [TFSI]-, creating stable ILs with low melting points. These BILs were applied as electrolytes to symmetric double layer capacitors comprised of carbon nanofoam paper (CNP) electrodes. Monomeric polyBILs were characterized using cyclic voltammetry, differential scanning calorimetry, thermal gravimetric analysis, broadband dielectric spectroscopy and compared to previously reported non-polymerizable analogs. Their operational voltage windows were studied in a two-electrode configuration using cyclic voltammetry. Then, galvanostatic charge/discharge cycling was performed to assess the performance and long-term stability of the cells.
Physical and Analytical Electrochemistry Division Max Bredig Award In Molten Salt and Ionic Liquid Chemistry Award Recipient Address
Authors: MacFarlane Douglas Robert
Published: December 2024

In this talk, I would like to reflect on my personal history in molten salt and ionic liquid research, focusing on why and how I became to be interested in the field. At the same time, I will acknowledge the many research collaborators who have made important contributions to my work.
The Specific Adsorption of Chloride Ions from Ionic Liquid
Authors: Siinor Liis , Ers Heigo , Luure August , Leuska Ermo , Pikma Piret
Published: December 2024

Interactions and processes that determine the characteristics of the electrode–ionic liquid (IL) interface are crucial for developing fundamental understanding and various applications1-2. This implies that the expected progress of electrochemical energy storage devices and other appliances relies on the success of describing these interfacial systems and processes in detail. Various factors define the interfacial properties of any electrode-electrolyte system3. These factors can be roughly divided into 3 groups: electrode-related (the effect of surface structural and electronic properties), electrolyte-related (the chemical composition and/or presence of additives), and external factors (applied potential, temperature, etc.). Numerous well-recognized research groups have described the properties of the electrode-IL interface. The consensus is that ILs form ordered interfacial layers at electrodes, while the interfacial processes are much slower than in other electrolytes4. Despite the consensus, numerous fundamental questions have yet to be answered.

The main aim of this work was to characterize the adsorption of chloride ions from the mixture of two ionic liquids based on the same 1-ethyl-3-methylimidazolium cation5.

Electrochemical impedance spectroscopy and cyclic voltammetry methods have been applied to study the electrochemical characteristics of the interface between Bi(111) and mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and 1-ethyl-3-methylimidazolium chloride (0-2 wt%).

Experimental results show that within the potential region of specific adsorption of Cl–, capacitance (C) values increased significantly compared to neat EMImBF4 and were limited by Gibbs adsorption effect at high Cl– concentration. The equilibration of the interface and the formation of a stable adsorbed layer of Cl– is a lengthy process timewise. The C values decrease in time, reaching a stable value after 36 h. Phase angle values confirmed that the kinetics of these processes is limited by the adsorption kinetic step in a wide range of alternative current frequencies. The findings are supported by in situ STM images, where a highly ordered structure was visualized.

References

Fedorov, M. V. et al., Chem.Rev.114 (5) 2978 (2014).

MacFarlane, D. R. et al., Phys.Chem.Chem.Phys. 12 (8) 1659 (2010).

Trasatti, S. Electrochim. Acta 37 (12), 2137 (1992).

Ers, H. et al., Electrochim. Acta 421, 140468 (2022).

Siinor, L. et al., J. Phys. Chem. C 128, 2722 (2024).

Acknowledgements

This work was supported by the Estonian Research Council Grants PSG249 and PRG676; the European Regional Development Fund under Project TK141 (2014-2020.4.01.15-0011), the Estonian Ministry of Education and Research Project TK210, and by the project “Increasing the knowledge intensity of Ida-Viru entrepreneurship” (ÕÜF12) co-funded by the European Union.
Electrochemical Hydrogen Evolution Using Proton Transport through Graphene Monolayers
Authors: Baranitharan Sekar , Motobayashi Kenta , Ikeda Katsuyoshi
Published: December 2024

Pursuing sustainable hydrogen, electrochemical Hydrogen Evolution Reaction (HER) is crucial. However, challenges arise during HER, including the dissolution of catalytic materials and the formation of hydrogen bubbles on the electrode surface. Bubbles that evolve at an electrode may result in undesired blockage of the electrocatalytic surface, and ion conducting pathways in the electrolyte resulting energy losses1. Our study addresses this issue using monolayer graphene as a two-dimensional electrode with proton permeability.

A graphene monolayer was synthesized using chemical vapor deposition (CVD) on a copper substrate. The fabrication process involved assembling the graphene monolayer on copper foil with nafion followed by hot pressing at 140°C for 2 minutes under 1.4 MPa pressure. Subsequently, this assembly was floated on Cu etchant (0.2 M (NH4)2S2O8 aqueous solution) facing Cu foil side overnight at 25°C and then rinsed Milli-Q water for several times. Platinum nanoparticles on graphene/nafion membrane was deposited using potential step method2. The electrochemical tests were carried out in 0.5 M H2SO4 vs RHE under argon (Ar) saturation using home-built electrochemical cell designed for proton permeable electrodes as illustrated Fig (a) and Cyclic voltammetry (CV) Fig (b) was performed Pt/Gr/N, Pt electrode at a scan rate of 50 mV/s.

The hydrogen evolution performance of Pt/Gr/N measured in the proton permeable transport configuration in 0.5 M H2SO4 as evidenced by cyclic voltammetry revealing an observed lower overpotential of 17 mV at 10 mA/cm²(Pt-ECSA) suggests that proton transport occurs through the graphene layer, facilitating the hydrogen evolution reaction (HER) in gas phase without the generation of gas bubbles in electrolytes. This leads to minimal H2 reoxidation on Pt, which results in a positive shift in the observed onset potential and higher current density. On the other hand, Pt electrode in the conventional proton diffusion transport configuration exhibited a slightly higher overpotential of 28 mV at the same current density per Pt-ECSA, due to the HER in the solution phase. Indeed, hydrogen oxidation reaction (HOR) during the backward potential scan ofs the CV was observed only in the case of the conventional Pt electrode.

1.Zhang C, Guo Z, Tian Y, et al. Nano Research Energy, 2: e9120063 (2023)

2.Domínguez-Domínguez, et al. J Appl Electrochem 38:259–268 (2008)

Figure 1
A Single Chamber Urea/Persulfate Fuel Cell: Optimization of Cathode to Use Peroxydisulfate Electron Acceptor
Authors: Kim Soeun , Kim Jiseon , Cho Kangwoo
Published: December 2024

Environmental and energy issues draw considerable attentions in the modern society. One of the options to simultaneously solve these issues can be a wastewater fuel cell to recover energy during wastewater treatment. The urea oxidation reaction (UOR) has been tackled to enhance the energy efficiency of electrochemical hydrogen production and/or fuel cell utilizing urea, an abundant nitrogenous pollutant in human (livestock) wastes, as an electron donor. In spite of the significant progresses on a direct urea fuel cell (DUFC), various problems were reported for real wastewater, in relation to the membrane fouling to hamper practical applications from urine. To this end, this study proposes a single chamber DUFC employing Ni-Cl as an anode, CuO/CN as a cathode, and peroxydisulfate (PDS) as an electron accepter. An ideal utilization of PDS should increase the open circuit voltage than O2, while catalytically activated PDS can eliminate aqueous pollutants (including urea) for urine treatment. The Ni-Cl anode was prepared by a simple HCl etching of Ni foam, enhancing the UOR activity compared to the mother foam. The CuO/CN cathode was prepared by a sequential electrodeposition and hydrothermal treatment. This presentation focuses on an enhanced catalytic activity of direct/indirect PDS reduction on the Ni-Cl and CuO/CN, as confirmed by cyclic voltammetry and constant load discharge of a single chamber urea/PDS fuel cell. In particular, this study interrogated the mechanism of urea oxidation in the single-chamber DUFC in comparison with a chemical PDS activation system. A proto-type single chamber fuel cell marked a maximum power density of 1.8 mW cm-2 with 0.3 M urea, to open a new era of urine fuel cell without usage of membrane and precious element catalysts.
Challenges in Accurate Calculation of Electrochemical Reactions Using First Principles Calculations: Water Adsorption on Pt(111) Surface Under Applied Potential
Authors: Shishkin Maxim , Yamaguchi Takeo
Published: December 2024

Modelling of chemical reactions controlled by an applied external potential could greatly enhance technological developments in the fields like electrochemical synthesis, fuel cells, water electrolysis and etc. Such modelling could be used for in silico search for more active and more stable catalysts, avoiding time consuming and costly experiments. However, a key prerequisite for reliable and successful modelling should be a close agreement between evaluated properties and their experimental observations.

In this presentation the fundamental reaction of water interactions with a surface of Pt electrode is discussed. We chose this reaction as a useful illustrative example where available experimental measurements, such as potentials of water adsorption and dissociation on Pt surface could be directly compared to the modelling for benchmarking of a computational accuracy. Herein, the ability of an employed DFT-based method with implicit model of solution is tested, addressing challenges such as limitations in accurate evaluation of materials work functions, approximate model of solution and difficulties in total energy evaluation under the constant potential.

As a first step, we point out to the problem of employing an experimental range of a potential of the standard hydrogen electrode (SHE), used as a reference in theoretical calculations in view of an inability of DFT to provide sufficiently accurate evaluation of materials work function and hence an operating potential. Secondly, we also show that upon hydration of a Pt surface there exists a peculiar non-monotonic change of a potential upon charging of a slab in contrast to monotonic relation for a clean Pt surface, which we explain by modification of water binding mechanism (presence of a dual charge in certain voltage range) with changing of a charge state of Pt surface (Fig. 1).

To characterise the binding mechanism of a water molecule to Pt(111) surface we analysed the partial density of states, Fukui function and density matrices of p-states of an oxygen atom of a water molecule upon adsorption. Based on our calculations we conclude that greater binding upon application of a higher potential is accounted for by a charge accumulation in the Pt-O interatomic space, in spite of an overall total charge decrease.

In summary our work provides a reliable methodology, that could be applied for analysis of reaction steps of electrochemical reactions on Pt surface under the applied external potential.

This presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Figure 1
The Weyl Semimetals MIrTe4 (M = Nb, Ta) as Efficient Catalysts for Dye-Sensitized Hydrogen Evolution
Authors: Samanta Manisha , Tan Hengxin , Yan Binghai , Lotsch Bettin Valeska
Published: December 2024

The prevalent global energy crisis calls for searching viable pathways for generating green hydrogen as an alternative energy resource. Dye-sensitized photocatalytic water splitting is a feasible solution to produce green hydrogen. However, identifying suitable catalysts has been one of the bottlenecks in driving dye-sensitized photocatalysis efficiently. In this work, we report a new class of electrocatalysts based on the layered Weyl semimetals MIrTe4 (M = Nb, Ta) for the Eosin Y (EY)-sensitized hydrogen evolution reaction (HER). NbIrTe4 and TaIrTe4 exhibit HER activities of ~18000 and 14000 µmol g-1 respectively, after 10h of irradiation with visible light. Time-dependent UV-Vis spectroscopy and high-pressure liquid chromatography coupled with mass spectroscopy analysis shed light on the reaction dynamics and enable a deeper understanding of the observed trend in hydrogen evolution rates for MIrTe4. MIrTe4 semimetals outperform transition metal-based Weyl semimetals in terms of catalytic HER activity using EY as photosensitizer and triethanolamine as the sacrificial agent. We hypothesize that the topology-related band inversion in MIrTe4 Weyl semimetals promotes a high density of M d-states near the Fermi level, driving their high catalytic performance. This study introduces a new class of layered Weyl semimetals as efficient catalysts, and provides perspectives for designing topology-enhanced catalysts.

Figure 1
Effects of Rb-Based Mixed Fluxes on Surface Crystal Growth of BaTaO₂N and Photocatalytic Activities
Authors: Tashiro Keito , Yamada Tetsuya , Yanagisawa Kazumichi , Tipplook Mongkol , Hayashi Fumitaka , Teshima Katsuya
Published: December 2024

Photocatalytic water splitting has been actively studied from the viewpoint of environmental issues as a method to produce hydrogen, a clean energy source, without using fossil fuels. Oxynitride BaTaO2N is a visible light responsive photocatalyst and is expected to have high energy conversion efficiency for hydrogen production using sunlight. In a previous study, single phase BaTaO2N crystals were successfully grown by the flux method. However, the maximum activity value is only about 500 µmol/h, which is insufficient to produce enough hydrogen for practical use. One of the reasons for this is unoptimized crystal surface, such as crystal face, and lattice defects. Flux method is known as an effective method to control crystal properties, but single flux is difficult to control these crystal properties at the same time. For example, although RbCl flux can reduce defect density by minimizing elemental contamination of BaTaO2N, it is highly volatile and not effective in controlling the crystal surface. Therefore, we considered the use of multiple fluxes at the same time. This allows appropriate modification of factors related to the flux reaction field, such as viscosity, melting point, and solute-solvent interaction, while avoiding elemental contamination. This leads to flexible adjustment of the crystal growth mode, which we believe will bring crystal growth closer to ideal conditions.

In this study, the effect of multi-flux on the growth mode and photocatalytic properties of BaTaO2N crystals was investigated. As an example, we report the crystal growth of BaTaO2N using mixed fluxes of RbCl, RbBr, and Rb2CO3. A single RbCl flux provided step-terrace surface structure of the BaTaO2N crystal, while an equimolar mixture of RbCl and RbBr resulted in a flatter and more rounded crystal. The visible-light responsive photocatalytic activity of the BaTaO2N crystals obtained with each flux was evaluated. The photocatalytic H2 evolution value of BaTaO2N grown in RbCl-RbBr mixed flux was about 30% of that grown in RbCl flux. This drastic change in activity may be explained by decrease of active crystal surface, including step-terrace one derived from mixed flux reaction field. We are now investigating the effect of step-terrace structure on photocatalytic activity, by tuning the surface structure using the mixed flux species. In the presentation, we will systematically report fine design of crystal growth, photocatalytic activity, and also the contribution mechanism of the mixed fluxes on them.

Acknowledgement

This work was partly supported by the NEDO Green Innovation fund projects, the Strategic Innovation Program (SIP) of the Cabinet Office, and joint research with a company.
Organic π-Conjugated Polymers as a Photoelectrocatalyst for Water-Splitting
Authors: Oka Kouki
Published: December 2024

Introduction

Hydrogen gas (H2
) is an important chemical feedstock; it is used as a reductant in petroleum refining, ammonia synthesis, the manufacture of stainless steel, and the production of core chemicals (e.g., methanol) and food (e.g., margarine). H2
is also regarded to be a critical and indispensable clean fuel for sustainable energy systems because of its extremely high energy density of 142 kJ g−1 (vs. 44 kJ g−1 for gasoline) and low pollution emissions.1) However, H2
is presently produced by conversion of hydrocarbons or fossil fuels and is accompanied by enormous energy consumption and greenhouse gas emissions. To realize carbon neutral and sustainable circulation technology, carbon-free and green H2
production methods, such as water-splitting, are required. 2)

Results and discussion

This presentation describes organic π-conjugated polymers as a novel photoelectrocatalyst towards water-splitting.2-4) π-Conjugated polymers synthesized without residual metals were developed to function in "water", which defied common sense, leading to this novel catalytic ability. In detail, (1) we succeeded in synthesizing polythiophene, which is a type of π-conjugated polymer, in a film form without residual metal by our unique iodine-vapor-phase polymerization method (2) We found that this polythiophene film worked as a novel photoelectrocatalyst that absorbs visible-light and highly efficiently reduces water to generate H2
. (3) In addition, based on a rigid π-conjugated polymer structure, this polythiophene film catalyzed water-splitting/ H2
production with surprisingly high durability (more than 1 month without no degradation). The development of environmentally-friendly organic catalysts that do not use precious metals will lead to the production of truly green H2
.

We will also describe developments to other catalytic functions (O2
reduction/ H2O2
production etc.) of organic π-conjugated polymers.

References

1) Schlapbach, L. et al., Nature, 2001, 414, 353-358.

2) Oka, K. et al., Adv. Energy Mater., 2021, 11, 2003724.

3) Oka, K. et al., Energy Environ. Sci., 2018, 11, 1335-1342.

4) Oka, K. et al., Adv. Energy Mater. 2019, 9, 1803286.

Acknowledgment

This work was partially supported by Grants-in-Aids for Scientific Research (No. JP23K17945, JP23H03827, JP24K01552) from MEXT, Japan. K. Oka. also acknowledges the support from Shorai Foundation for Science and Technology, TEPCO Memorial Foundation, Amano Industry Technology Laboratory, Sugiyama Houkoukai, The Yamada Science Foundation, Kenjiro Takayanagi Foundation, Kansai Research Foundation for Technology Promotion, and JACI Prize for Encouraging Young Researcher.
(Invited) Integration of Electrochemical Oxidation and Photocatalytic Degradation for Water Purification and Wastewater Treatment
Authors: Chen Aicheng
Published: December 2024

The contamination of water with a myriad of pollutants has become an increasingly global issue in recent decades due to the widespread expansion of industrialization, which has tremendously propagated the development of large-scale industries and increased metallurgic production. Water contamination is anticipated to increase at least two-fold over the next 20 years. In this talk, a new design of an integrated electrode is introduced for the photo-electrochemical purification of water from a wastewater treatment plant. A nanoporous TiO2 structure, directly grown on a Ti substrate by anodization, and a RuO2-IrO2-based electrode was utilized as the photocatalyst and the electrocatalyst, respectively. Photocatalytic and electrocatalytic activities were synergistically combined to achieve an integrated and highly catalytically active electrode. Our experimental results have shown that the efficient enablement of photocatalytic and electrocatalytic activities within a single integrated electrode may be achieved via the new design. The applicability of this integrated electrode system was also tested in a pilot plant at a local water treatment facility. The pilot plant testing results revealed that much more efficient removal of organic waste was accomplished using the integrated electrode system as compared to only photocatalyst or electrocatalyst. The synergistic effect of the integrated bi-functional electrodes will be discussed.
(Invited) Organic Molecule and Polymer Nanoparticles in Biohybrid Photocatalysis
Authors: Tian Haining
Published: December 2024

Organic molecule and polymer nanoparticles have found extensive application in photocatalysis for solar fuel production, owing to their excellent dispersion in water and customizable optical properties [1]. These nanoparticles, characterized by their small size and modifiable surface charge through different surfactants, present a unique opportunity for integration with bio-systems. While organic nanoparticles have been traditionally employed as fluorescent probes and phototherapy reagents [2], their exploration within bio-systems for solar fuel production remains underexplored. In our recent research, we present innovative approaches utilizing organic particle-based bio-hybrid systems for solar fuel production.

In one study, we successfully integrated polymer particles (Pdots) with FeFe hydrogenase, as evidenced by Cryo-EM and electrophoresis revealing a visually detectable interaction between Pdots and hydrogenase [3]. The Pdots-hydrogenase system demonstrated remarkable performance in light-driven hydrogen production.

In another investigation, we immobilized Pdots onto the membrane of Ralstonia eutropha H16 (RH16) bacteria and employed natural redox shuttle, utilizing natural red as a mediator between Pdots and RH16 bacteria to facilitate the transport of protons and electrons [4]. The resulting Pdots-RH16 bio-hybrid system exhibited a threefold increase in the yield of poly(3-hydroxybutyric acid) compared to the original RH16.

Furthermore, I will provide insights into the progress of our work within the EU Photo2Fuel project, specifically focusing on the development of biohybrid systems for CO2 fixation.

References

[1] Pavliuk M., et al., Chem. Soc. Rev., 2022, 51, 6909-6935

[2] Wu C., et al., Angew Chem Int Ed Engl. 2013, 52(11), 3086–3109

[3] Pavliuk M., et al., J. Am. Chem. Soc. 2022, 144, 30, 13600–13611

[4] Yu W., et al., ACS Appl. Mater. Interfaces, 2023, 15, 1, 2183–2191
Cu-Doped InP Quantum Dots: Charge Carrier Dynamics and Photocatalytic Hydrogen Production
Authors: Shih Jen An , Pu Ying-Chih , Hsu Yung-Jung
Published: December 2024

Harnessing solar energy for photocatalytic hydrogen production represents a promising path towards sustainable energy solutions. Quantum dots (QDs) offer distinct advantages over traditional metal oxides, including boasting tunable bandgaps and enhanced light absorption in the visible spectrum. In the present study, InP QDs were chosen as the backbone for photocatalytic hydrogen production, leveraging their environmentally friendly properties and tunable bandgap, which extends into the near-infrared region. By introducing Cu dopants to modify the carrier dynamics of InP QDs, the localization of photogenerated charge carriers was effectively enhanced, resulting in improved photocatalytic performance of InP QDs. This study underscores the potential of Cu-doped InP QDs as efficient and eco-friendly photocatalysts for solar-driven hydrogen production. Time-resolved photoluminescence spectroscopy was employed to analyze the quantitative impact of Cu dopants on the interfacial charge dynamics, offering insights into optimizing the charge transfer processes of QDs for enhanced solar hydrogen production efficiency.
First Principles Modeling of Polaron Formation and Optical Spectroscopy on Titanium-Based Oxides for Oxygen Evolution Photocatalysis
Authors: McBride Shay , Lang Moritz , Cuk Tanja , Hautier Geoffroy
Published: December 2024

The exact mechanism and surface coverage present on (photo)-catalysts used for the oxygen evolution reaction (OER) remain elusive. Time-resolved in-operando spectroscopy on model single crystal surfaces has started to clarify these questions but requires strong first- principles theoretical support to facilitate the interpretation of the spectroscopic signatures. The trapping of photo-generated holes as polarons on adsorbs at the catalyst surface is a key step in the photo-driven OER. We model from first principles the optical signature of these hole polarons on OER intermediates (OH2, OH, O) on titanium-based photocatalysts (SrTiO3 and TiO2), and use our results to assign experimental absorptive peaks to hole trapping at specific adsorbates.
(Invited) Unveiling the Structure-Function Relationships of Materials Using in Situ/Operando Neutron Reflectometry
Authors: Wang Hanyu , Candeago Riccardo , Doucet Mathieu , Su Xiao , Browning Jim
Published: December 2024

Neutrons have many extraordinary properties, including no overall charge, highly sensitive to light elements like hydrogen and carbon, magnetic moment, and power of polarization, etc. All these characteristics make them excellent probes of materials, providing details about the structure and motion of atoms that cannot be easily obtained with other research techniques. Neutron reflectometry (NR), a neutron scattering technique, is a powerful tool to examine surface and interfacial structures of thin films in a non-destructive and non-invasive fashion. The Liquids Reflectometer (LR) at the Spallation Neutron Source at Oak Ridge National Laboratory measures specular neutron reflectivity in a horizontal sample geometry, and tracks changes of layer thickness, scattering length density, and roughness as a function of depth. LR provides valuable information over a wide variety of scientific and technological applications, such as, interfacial reactions in energy storage materials, phase separation in polymer films, surfactants at interfaces, biological membranes in intermolecular interaction, protein adsorption, and so on. The exceptional sample environment at LR offers the capability to conduct in situ electrochemistry to probe the morphological and structural changes of solid/liquid interfaces during operation as a function of chemical and electrochemical gradients over time. Furthermore, event mode data collection at LR can be carried out continuously over a reduced Q range and binned into 60-second intervals. The improved time resolution of the NR measurement can help elucidate the kinetic behavior of surface/interfaces under dynamic conditions and bring a unique perspective to equilibrium studies. A specific example of applications in electrochemically modulated separation for water remediation by using in situ/operando neutron reflectometry will be presented. The example study sheds light on fundamental understanding of selectivity mechanisms at electroactive interfaces, with direct benefits to the water separations research field. In addition to neutron techniques, some complementary capabilities for surface chemistry and electrochemistry available at both user facilities (Center for Nanophase Materials Sciences and Neutron Scattering Division) will also be outlined. Together, they will play a key role in creating new, and more efficient systems through rationally design of the structure and operating conditions.
Laboratory-Based X-Ray Emission Spectroscopy (XES) for Determination of Oxidation State and Ligand Species
Authors: Aronstein Paul , Lebens-Higgins Zachary , Holden William , Mortensen Devon
Published: December 2024

Identification of oxidation state and ligand species is often challenging, requiring arduous preparation and destructive analytical techniques which inhibit rapid analyses. Advancements in laboratory-based X-ray emission spectrometers (XES) are addressing this issue, facilitating consistent access to element-specific bulk chemical analysis of oxidation state and ligand speciation in users’ own labs. Intended to simplify and expand access to this powerful technique for both new and existing members of the XAS community, everyday analysis is a game-changer which enables researchers to control their experiment like never before. Synchrotron-like data quality is achievable within minutes even on trace elements (few hundred PPM). Utilizing a Rowland-circle geometry, easyXAFS spectrometers support a broad energy range (2-25 keV) capable of XES analysis of over 50 elements ranging from phosphorus through the actinides. Herein we discuss the benefits of XES for determination of oxidation state and ligand speciation highlighting previous and ongoing research in electrocatalysis, cathode coatings, battery charge/discharge operando measurements.

Figure 1
Operando Electrochemical Raman Spectroscopy Studies of Working Electrodes in (photo)Electrocatalytic Water Splitting
Authors: Qiu Jingjing , Lin Timothy , Yap Kyra M. K. , Jaramillo Thomas F. , Nielander Adam C.
Published: December 2024

Raman spectroscopy has been applied as a vibrational spectroscopic technique in the field of chemical, materials, and life sciences. Recently, the operando electrochemical Raman spectroscopy has received more research attention for the characterizations of working electrodes in (photo)electrochemical catalysis. This technique allows for the characterization of the fate of electrocatalysts on the surface of the working electrodes under electrochemical reaction conditions, which is crucial to determine the chemical identify of the electrocatalysts.

We apply the operando electrochemical Raman spectroscopy to study the anodes and cathodes in the (photo)electrocatalytic water splitting process, which is an important process to generate the clean energy hydrogen (H2) gas from water using solar energy and electricity. Specifically, we study the stability of the electrocatalyst molybdenum sulfide (MoS2) on silicon (Si) photocathode for the hydrogen evolution reaction (HER) and the electrochemical transformation of the electrocatalyst cobalt hydroxide (Co(OH)2) on nanostructured gold (Au) photoanode for the oxygen evolution reaction (OER). We have identified the correlation between the morphological changes and vibrational features of the MoS2 layer and detected the potential-dependent vibrational features of the Co(OH)2 film.
Raman Imaging the Evolution of Additive-Free Silver Molybdate Electrodes
Authors: Smith Paul
Published: December 2024

For many contemporary materials in electrochemical energy storage research, construction of composite electrodes including carbon and binder remain necessary, despite the fact that decreased inactive components and high loading masses are targets for the next generation of energy dense batteries. Challenges that result from composite preparations include a limitation in the gravimetric energy density as well as electrode heterogeneity, which may cause long-term loss of performance. Mixed silver-metal oxides and phosphates are a class of materials which may minimize, and potentially circumvent, the need for composites because they can produce an electrically conductive network of silver metal on reduction. Mapping studies which elucidate where the silver network appears are known, but have not kept pace as mixed silver-metal oxides are studied for new applications such as aqueous zinc-ion batteries. Here, we use Raman imaging spectroscopy to map the evolution of Zn/Ag2Mo2O7 aqueous batteries, and report on the ZnMoOx phases produced in this system. We show that in this system, the silver metal is also able to be mapped by taking advantage of surface-enhancing principles. Collectively, this electrode pair will be an example of how electron movement in 2D and 3D space can be mapped solely with Raman spectroscopy.
Investigating the Impact of Pt(hkl) Surface Structure on Electrochemical Double Layer Capacitance: Aimd Simulations and Experimental Insights
Authors: Chaudhary Payal , Nouri Mohammad Reza , Alexandrov Vitaly
Published: December 2024

A comprehensive understanding of the electrical double layer (EDL) properties is essential to engineer electrochemical systems. The classical theory of EDL can reasonably explain experimental observations for only a few ideal systems like the liquid metal mercury electrodes, which are not suitable for practical applications. The EDL at solid electrodes, which are often used in electrochemical energy systems, have non-trivial dependences from several factors such as the electrode structure, its chemical composition, and complex interactions between the electrode surface and electrolyte species. Taking these factors into account requires a more detailed description of the EDL than that provided by the classical EDL theory.

In this study, we focus on the double layer capacitance as a key property of the EDL to rationalize experimental measurements of the capacitance as a function of the electrode surface structure. We employ ab initio molecular dynamics simulations to explicitly model several Pt(hkl)/water interfaces considering a series of flat and stepped surfaces at the potential of zero charge. We find that the orientation of water dipole moments at the interface depends strongly on the surface atomic structure, which can then influence the EDL capacitance. Our results suggest that simply by introducing surface defects such as steps on the Pt surface, the EDL capacitance can be varied significantly. We discuss our computational results in light of recent experimental data reported in J. Am. Chem. Soc. 2024, 146, 6, 3883–3889 and prior studies. We believe that the obtained insights are essential in advancing the fundamental understanding of the effect of electrode atomic structure on the basic electrochemical properties of electrocatalytic systems.
Predicted Current Density Response Versus Applied Potential for Five Crystallographic IrO2 Facets: Comparison with Thin Film Experiment
Authors: Kwon Soonho , Stoerzinger Kelsey A , Rao Reshma R , Qiao Liang , Goddard William A , Shao-Horn Yang
Published: December 2024

Iridium oxide (IrO2) stands out as the most effective catalyst for the oxygen evolution reaction (OER), a pivotal component of proton exchange membrane (PEM) electrolyzers. Despite its exceptional catalytic prowess, the kinetics of this reaction still impose limitations on the efficient production of green H2, thereby inflating costs and impeding broader commercialization. The catalytic activity of IrO2 for OER is influenced by its local chemical and atomic environment, wherein distinct crystallographic facets with unique atomic arrangements can induce significant variations even with the same bulk composition.

In this study, we examine the OER performance across five distinct rutile IrO2 facets. Through DFT calculations, we predict cyclic voltammetry (under the water oxidation potential) and compare directly to the results to experiments conducted on IrO2 thin films for validation. Unlike pure metallic systems characterized by degenerate active sites resulting in broad single redox peaks, or homogeneous systems where redox reactions occur at metallic centers, active sites on metal oxide surfaces exhibit localization yet remain interconnected via various types of oxygen bonds. This unique attribute introduces additional considerations that must be included to interpret redox behavior, because interactions between adjacent intermediates alter their identities differently for different applied potentials. We find that multiple redox features can overlap while a single type of redox couple can be associated with multiple redox features.

To elucidate the OER activity under operational conditions (> 1.23 VRHE), we conducted grand canonical calculations to explicitly capture the dependence of reactions on the applied potential, with particular emphasis on non-electrochemical steps such as O-O coupling. Through the construction of various possible OER pathways and amalgamating their energy landscapes into a unified microkinetic scheme under steady-state assumptions, we successfully replicate the experimental OER current density for each of the five facets. Our analysis unveils mechanistic disparities between nucleophilic attack and direct oxo coupling across facets, predicting rates as a function of applied potential and identifying the rate-limiting steps.

Our approach provides a thorough comprehension of the OER mechanism at the atomic level, offering valuable insights into the structural characteristics that enhance or inhibit the OER activity of IrO2. We expect these insights to have implications for understanding the structural effects on other heterogeneous catalysts which should aid the development of more efficient electrocatalysts.
Bridging Physics-Informed and Data-Driven Materials Designs to Catalyze Deep Decarbonization
Authors: Peng Jiayu
Published: December 2024

Electrifying and decarbonizing key industrial sectors, including chemical and materials industries, as well as transportation and aviation, is a pressing mission of our time. Industrial players and governments worldwide have set ambitious targets to reduce carbon emissions, which need to be decreased to net-zero around mid-century in order to address global warming and climate change. For such deep decarbonization, it is crucial to develop unprecedented materials, such as electrocatalysts that can efficiently and steadily produce green chemicals and fuels at scale and generate renewable electricity on demand. In this talk, I will introduce how a joint computational–experimental approach can be established to accelerate catalyst materials design using first-principles atomistic simulations, synchrotron X-ray spectroscopies, and physics-inspired machine learning. I will highlight how mechanistically elucidating and quantitatively controlling the electronic structure of transition metal compounds can effectively alter their chemical bondings, modulate key reaction barriers toward dissolution and electrocatalysis, and thus influence their durability and reactivity, respectively, offering physics-driven guiding principles for optimizing their catalytic performance. Moreover, I will demonstrate how combining machine learning with materials physics can accelerate the discovery of multicomponent oxides—a new class of materials with too-complicated atomic orderings for an exhaustive investigation—through the development of machine-learning models that accurately predict ordering-dependent materials properties by capturing intrinsic symmetries. To conclude, I will discuss new opportunities for further resolving fundamental knowledge gaps between the structural, reaction, and compositional complexities of electrocatalyst surfaces to fully unlock transformative materials design for catalyzing sustainability and decarbonization.
(Invited) Operando Probes of Site Densities, Energetics and Activity in Oxygen Evolution Catalysis
Authors: Stephens Ifan
Published: December 2024

Theoretical studies have revealed the kinetics of oxygen evolution are controlled by the binding energies of reaction intermediates. However, those simulations are based on idealised single crystal structures. Little is known about the catalytically active phases on high surface area catalysts.

In this contribution I will show how operando optical spectroscopy of oxygen evolution catalysts can yield (i) site densities (ii) binding energies of intermediates and (iii) turnover frequencies. We reveal the role of adsorbate-adsorbate interactions on state-of-the-art iridium2-4 and cobalt5 based catalysts, including molecular catalysts and oxides. I will correlate electrochemical measurements to operando optical spectroscopy, X-ray absorption spectroscopy and secondary ion mass spectrometry. Density functional theory measurements provide a molecular scale explanation for the observed phenomena.

Man, I. C., Su, H. Y., Calle-Vallejo, F., Hansen, H. A., Martínez, J. I., Inoglu, N. G., Kitchin, J., Jaramillo, T. F., Nørskov, J. K. & Rossmeisl, J. ChemCatChem 3, 1159, (2011).

Liang, C., Rao, R. R., Svane, K., Hadden, J. H. L., Moss, B., Scott, S. B., Sachs, M., Murawski, J., Frandsen, A., Riley, D. J., Ryan, M. P., Rossmeisl, J., Durrant, J. R. & Stephens, I. E. L. Nature Catalysis, (2024 in press).

Bozal-Ginesta, C., Rao, R. R., Mesa, C. A., Wang, Y. X., Zhao, Y. Y., Hu, G. F., Anton-Garcia, D., Stephens, I. E. L., Reisner, E., Brudvig, G. W., Wang, D. W. & Durrant, J. R. J. Am. Chem. Soc. 144, 8454, (2022).

Liang, C., Katayama, Y., Tao, Y., Morinaga, A., Moss, B., Celorrio, V., Ryan, M., Stephens, I. E. L., Durrant, J. R. & Rao, R. R. J. Am. Chem. Soc., (2024).

Moss, B., Svane, K. L., Nieto-Castro, D., Rao, R. R., Scott, S. B., Tseng, C., Sachs, M., Pennathur, A., Liang, C., Oldham, L. I., Mazzolini, E., Jurado, L., Sankar, G., Parry, S., Celorrio, V., Dawlaty, J. M., Rossmeisl, J., Galán-Mascarós, J. R., Stephens, I. E. L. & Durrant, J. R. J. Am. Chem. Soc., (2024).