bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain-Stabilized 1T Phase Ruthenium Sulfoselenide Monolayer Nanotubes for Oxygen Reduction Reaction in Alkaline Medium
Authors: Kim Myeong-Geun , Lee Dong Wook , Choi Daeil , Yoo Sung Jong
Published: July 2022

Backgrounds: In pursuit of sustainable development, a fuel cell become a key device that can convert chemical energy in hydrogen and oxygen into electrical energy. In this field, the sluggish reaction kinetics of the oxygen reduction reaction (ORR) on cathode side of fuel cell has been a key issue hindering large–scale applications. Although many efforts have been devoted to the development of efficient electrocatalysts for ORR, platinum (Pt)–based catalysts remain the most efficient electrocatalysts owing to their high intrinsic activity. However, their reserve–scarcity and low stability limit their widespread use.

Strategy: Therefore, it is highly desirable to develop electrocatalysts with high catalytic activities and stability as well. Among various strategies, metal chalcogenides have led to remarkable electrochemical performances beyond those of pure metals. Also, they have unique characteristics such as multiple crystal phases (e.g., 1H, 2H, 1T, and 1T’); the phase of 1H and 2H correspond to semiconductor, whereas the 1T and distorted 1T’ are metallic phases. Generally, the metallic phase has more active sites and higher electrical conductivity, making it favorable for electrochemical reactions compared to other phases. However, the metastability of 1T phase makes it challenging to directly prepare 1T metal chalcogenides; even, the prepared 1T material easily convert back to stable 2H (or cubic) phase under ambient conditions.

Results: Herein, we prepared 1T phase Ru(SxSe1-x)2 (x = 0, 0.2, 0.5, 0.8, and 1) with a shape of monolayer nanotubes (NTs), and they showed remarkable ORR activity and stability as well. The Ru(SxSe1-x)2 nanotube containing abundant anion vacancies was generated from Ru seed particle, which is confirmed by ex-situ TEM, EDS, and EPR. Typically, most nanotubes (e.g., TiO2, and MoS2) are generated via a roll-up mechanism, where the large size of nanosheet is necessary to roll up a sheet into a nanotube; however, the process is not suitable for ultra-small (ø <3 nm) nanotubes. The Ru(SxSe1-x)2 nanotube with a diameter of ø = 1.5 nm takes advantages of larger surface area and more catalytic active sites as well. Moreover, a strain induced by curvature of the nanotube and/or anion vacancies can lead to new bond identities (e.g., bond length and bond angle), resulting in phase stabilization of 1T. In effect, the 1T Ru(S0.8Se0.2)2 nanotubes not only exhibited remarkable ORR activities (E1/2 = 0.864) comparable to commercial Pt/C, but also showed superior durability under alkaline ORR conditions. The electrochemical property was maintained after an accelerated durability test (ADT) for 10K cycles or a long-term air exposure for 6 months. Our results pave the way for the synthesis of stable 1T phase metal chalcogenides, particularly for efficient alkaline oxygen reduction reaction.

Figure 1
Electrocatalytic Activity of Platinum-Nickel Layers Deposited on Nickel Foam for Formic Acid Oxidation in Acidic and Alkaline Media
Authors: Nacys Antanas , Simkunaite Dijana , Sebeka Benjaminas , Upskuviene Daina , Balciunaite Aldona , Zabielaite Ausrine , Jasulaitiene Vitalija , Tamasiunaite Loreta , Norkus Eugenijus
Published: July 2022

The performance of direct formic acid fuel cells (DFAFCs) is greatly determined by the catalyst materials. Pt nanoparticles-based heterogeneous structures are among the most important substances for the oxidation of formic acid (FAO). In this study, Ni foam catalyst layered with platinum has been investigated as the catalyst for the oxidation of FAO in acidic and alkaline media. The catalyst has been fabricated via a two-step procedure involving the electroless deposition of the Ni layer using sodium hypophosphite as a reducing agent and subsequent electrodeposition of the platinum layer. In this work, Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and X-ray Diffraction have been used to characterize the morphology, structure, and composition of the prepared catalysts. The electrochemical behavior of the bare Pt, Ni/Ni foam, and PtNi/Ni foam electrodes towards the oxidation of formic acid in acidic and alkaline media was evaluated using cyclic voltammetry.

It was found that the PtNi/Ni foam catalyst has a significantly higher electrochemically active surface area of Pt equal to ca. 71 cm2 than pure Pt. Moreover, the PtNi/Ni foam catalyst shows an enhanced electrocatalytic activity towards the FAO via direct pathway in both acidic and alkaline medium compared to those of Ni/Ni and pure Pt electrodes. Furthermore, the prepared PtNi/Ni foam catalyst exhibits greater tolerance of CO than the single-metal Pt in acid solution. Concomitantly, the PtNi/Ni foam catalyst is tolerant to CO poisoning n alkaline media demonstrating high poison removal ability. The PtNi/Ni foam catalyst seems to be a promising future anode material for DFAFCs.
(Digital Presentation) Oxygen Reduction Activity, Durability and Structural Transformation of Pt-Ni Nanowires in the Presence and Absence of Pt-Ni Nanoparticles
Authors: Kato Masaru , Iguchi Yoshimi , Kato Yuta , Li Tianchi , Zhuang Yu , Yagi Ichizo
Published: July 2022

Carbon-supported Pt-M (M=Ni or Co) nanoparticles (NPs) have been intensively studied as oxygen reduction reaction (ORR) catalysts for the cathode of polymer electrolyte fuel cells. Under electrocatalytic conditions, these catalysts are known to degrade involving particle detachment, agglomeration and metal dissolution. To develop highly durable ORR electrocatalysts, these phenomena can be suppressed by strong metal/support interactions[1,2] or even utilized as self-healing or sacrificial processes.

We present the ORR activity, durability and structural transformation of carbon-supported Pt-Ni nanowires (NWs) in the presence and absence of NPs.[3] In the presence of NPs, NPs were dissolved, and NWs were converted to form branched nanostructures during potential cycles. Because the similar structural transformation of NWs occurred even in the absence of NPs, the structural transformation is an intrinsic phenomenon during potential cycles. Interestingly, the ORR activity increased and the Pt dissolution was suppressed during potential cycles in the co-presence of Pt-Ni NWs and NPs. The electronic and surface structures are also changed before and after potential cycles and will be discussed based on physicochemical measurements including in situ Pt L
3-edge X-ray absorption spectroscopy.

This work was supported by NEDO.

References

[1] M. Kato, K. Ogura, S. Nakagawa, S. Tokuda, K. Takahashi, T. Nakamura, I. Yagi, ACS Omega, 3, 9052–9059 (2018).

[2] M. Kato, R. Nakahoshiba, K. Ogura, S. Tokuda, S. Yasuda, K. Higashi, T. Uruga, Y. Uemura, I. Yagi, ACS Appl. Energy Mater., 3, 6768-6774 (2020).

[3] M. Kato, Y. Iguchi, T. Li, Y. Kato, Y. Zhuang, K. Higashi, T. Uruga, T. Saida, K. Miyabayashi, I. Yagi, ACS Catal., 12, 259-264 (2022).
(Invited) Photoelectrochemical Glycerol Oxidation to Value-Added Commodity Chemicals Using BiVO4-Based Photoanodes
Authors: Hilbrands Adam , Choi Kyoung-Shin
Published: July 2022

To create a functional photoelectrochemical cell (PEC) for solar fuels production, a cathode and anode reaction must both be chosen and optimized. In order to generate clean energy, a renewable resource such as water, nitrogen, or biomass, is typically reduced at the photocathode to generate H2, ammonia, or carbon-based fuel. In aqueous media, the anode reaction is typically water oxidation, as water is renewable and available in the cell. However, the product of water oxidation, O2, is not very valuable. As such, in recent years attention has been directed to finding a more attractive oxidation reaction that forms a value-added product that can be paired with reduction reactions of interest. Ideally, this reaction would consist of renewable, abundant, and affordable feedstock, such as biomass, that can be readily oxidized to a more valuable compound.

The photoelectrochemical oxidation of glycerol to value-added commodity chemicals fits these criteria. Glycerol is the main byproduct of biodiesel production, and as such is cheap and abundant. As investment in clean fuels increases, the production of biodiesel will continue to increase, leading to an overabundance of glycerol, which can create storage and environmental issues. Developing systems to valorize glycerol will ensure sustainable biodiesel production and advance the transition to renewable fuels. Glycerol consists of three alcohol groups, and many oxidation pathways are possible, with the most profitable being the selective oxidation of the secondary alcohol to a ketone to make dihydroxyacetone (DHA). This conversion yields an over 200-fold value increase from $0.66 to $150 per kilogram. Thus, photoelectrochemical DHA production can provide an opportunity to make PEC operation more profitable while improving the sustainability of the biodiesel industry.

BiVO4 is a good candidate for photoelectrochemical glycerol oxidation as it has a favorable band gap (2.4eV), excellent charge separation, and low water oxidation selectivity. In this presentation, we report our recent results obtained for photoelectrochemical glycerol oxidation using a BiVO4 photoanode. We will discuss various surface modifications of BiVO4 that we employed to elucidate the reaction mechanisms and to maximize the efficiency and selectivity for DHA production.
(Invited) Dye-Sensitized Photoelectrochemical Cells with Hydrogen-Atom Transfer Co-Catalyst for Oxidative Lignin Decomposition
Authors: Lee Jae-Joon
Published: July 2022

The lack of selectivity of oxidative-cleavage is one of prime issues for decomposition of lignin, because of the harsh reaction environments, such as high temperature and high pressure, in general. Dye-sensitized photoelectrochemical cells with a homogenous hydrogen-atom transfer co-catalyst with Ruthenium-complex based sensitizer as a photocatalyst (e.g. RuC ((bis-2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)Ru(II)) (HAT-DSPEC), was suggested as an alternative and this system exhibited the conversion efficiency of over 90% at 24 hour illumination (AM 1.5G) although these metal-complex based sensitizers, having relatively low values of absorption coefficient, generally are not cost-effective and stable enough.

In this study, for highly stable HAT-DSPEC process, metal complex sensitizer was replaced by organic dye(5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid, L1) which has high stability and molar absorption coefficient. Also three kinds of organic nitroxyl mediators (HAT) was used such as 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), 4-Acetamido-TEMPO (ACT) and 9-azabicyclo[3,3,1]nonan-3-one-9-oxyl (Keto-ABNO). Each HATs (TEMPO, ACT and keto-ABNO) showed different reactivity and conversion efficiency (about 65%, 60% and 88%). In HAT-ODSPEC(organic dye-sesitized photo-electrochemical cell), Keto-ABNO showed highest conversion efficiency with 2-ol(S,G). This HAT-ODSPEC process provides a unique foundation to perform selective C−C bond cleavage for real lignin conversion technologies.
(Invited) Photo-SECM Measurements of Water Splitting at Single Semiconductor Particles
Authors: Askarova Gaukhar , Hesari Mahdi , Barman Koushik , Mirkin Michael
Published: July 2022

Understanding and improving the properties of photocatalysts can have important implications for energy conversion and storage. Because the activity of heterogeneous catalysts depends strongly on local atomic structures, probing (photo)catalytic reactions at specific local sites is critically important. We have recently reported the use of scanning electrochemical microscopy (SECM) for nanoscale imaging of photoelectrochemical processes at semiconductor surfaces. To illuminate a microscopic portion of the substrate surface facing the SECM probe, a glass-sealed, polished Pt tip simultaneously serves as a nanoelectrode and a light guide. In this paper, we present the results of first nanoscale SECM and photo-SECM experiments with single BiVO4 and SrTiO3 particles. Local mapping of oxygen and hydrogen fluxes produced by water splitting at single semiconductor particles was carried out using chemically modified SECM nanotips.
Modeling the Effects of Coatings, Light Absorption, and Mass Transfer on Solar-to-Hydrogen Efficiencies in Z-Scheme Photocatalytic Reactors
Authors: Barrera Luisa , Stinson Robert , Ardo Shane , Esposito Daniel V. , Bala Chandran Rohini
Published: July 2022

Z-scheme photocatalytic particles in an aqueous solution with soluble redox shuttles present a promising pathway for solar water splitting to produce hydrogen. Tandem light absorbers more efficiently utilize the incident solar spectrum, and physically separating hydrogen and oxygen production sites offers a safe reactor design. Theoretically, these reactor designs are projected to achieve competitive solar-to-hydrogen efficiencies as large as 34% with idealized light absorbers, state-of-the-art hydrogen, and oxygen evolution catalysts, selective reactions, and rapid mass transfer rates1. However, practical demonstrations have been limited to significantly lower efficiencies that are less than 1%. In part, this effect is attributed to competing and undesired redox reactions occurring at the particle–cocatalyst–electrolyte interface. In this work, we develop and apply an expanded equivalent circuit model to test the effectiveness of coatings to achieve reaction selectivity by manipulating redox species transport to functional interfaces2. This model formulates light absorbers as photodiodes and accounts for the effects of kinetic and mass-transfer resistances for both the desired and competing redox reactions. Transport properties in the coatings are parametrized as a function of its thickness, species permeabilities, and solubility coefficients. Mass transport rates are computed as a function of species concentration and concentration boundary layer thickness. Additionally, spatial profiles of light intensity in a reactor with multiple light absorbers are evaluated for an ensemble of (a) optically thin semitransparent slabs, and (b) particles that can absorb and scatter incident light. Results reveal the interplay of light absorption behavior, coating transport and kinetic properties, and mass transfer rates on the predicted solar-to-hydrogen efficiencies. An optimum concentration of light absorbers is shown to maximize light absorption while minimizing the extent of competing reactions. Results are further interpreted to provide insight on design principles for selective coatings to maximize efficiency. Overall, the modeling framework provides new capabilities with a tractable approach to traverse the multidimensional dependencies of various parameters on the solar-to-hydrogen efficiencies for Z-scheme photocatalytic systems.

References

Keene, S., Bala Chandran, R. & Ardo, S. Calculations of theoretical efficiencies for electrochemically-mediated tandem solar water splitting as a function of bandgap energies and redox shuttle potential. Energy Environ. Sci.
12, 261–272 (2019).

Barrera, L. & Bala Chandran, R. Harnessing Photoelectrochemistry for Wastewater Nitrate Treatment Coupled with Resource Recovery. ACS Sustain. Chem. Eng.
9, 3688–3701 (2021).
(Invited) Nanoscale Electrocatalyst/Semiconductor Interfaces As Charge-Carrier-Selective Contacts in Photocatalytic and Photoelectrochemical Systems
Authors: Boettcher Shannon W. , Kaufman Aaron James , Shen Meikun
Published: July 2022

Charge-carrier-selective interfaces between electrocatalyst particles and semiconductor light absorbers are critical for solar photochemistry but controlling their properties is challenging. In this talk I will show that the nanoelectrode tip of an atomic-force-microscope cantilever can sense the surface electrochemical potential of thin-film and nanoscale electrocatalysts coating semiconductor photoelectrodes during operation. This technique allowed us to unambiguously show that metal (oxy)hydroxide layers act as both hole collectors and oxygen-evolution catalysts on metal-oxide photoanodes such as Fe2O3 and BiVO4. We also discovered the critical role that heterogeneous interfacial barrier heights, and a related nanoscale pinch-off effect, play in building carrier-selective interfaces in semiconductor photoelectrodes for generating fuel from sunlight. As specific example, thin films and nanoparticle of Pt hydrogen-evolution catalysts on p-InP, a high-performance photocathode material, along with macroscopic and nanoscopic electrical and chemical analysis, are used to show how hydrogen alloying, the pinch-off effect for nanoscale contacts, and the formation of a native surface oxides all play different roles in creating charge-carrier-selective junctions. The sum of these new insights can be broadly applied to photocathodes, photoanodes, and overall water-splitting systems to control charge-carrier selectivity and improve performance.
(Invited) Surface Photovoltage Spectroscopy on BiVO4, Gallium Phosphide, and CuGa3Se5 Photoelectrodes in Contact with Aqueous Electrolytes
Authors: Osterloh Frank E , Daemi Sahar , Kundmann Anna , Becker Kathleen , Cheng Ye
Published: July 2022

The quasi-Fermi level splitting energy (photovoltage) is important for the solar to fuel conversion efficiency of photocatalysts and photoelectrodes. While electrochemical measurements can provide the electrochemical potential of the majority carriers at the semiconductor back-contact, the photovoltage, and the potential of the minority carriers at the front semiconductor/electrolyte are more difficult to determine experimentally, due to the lack of a direct electrical connection. Here we show that surface photovoltage spectroscopy (SPS) on photoelectrode films in contact with aqueous electrolytes can provide photovoltage information. For the measurements the semiconductor films (BiVO4, CuGa3Se5) or wafers (n-GaP or p-GaP) are immersed in aqueous electrolytes and placed underneath a vibrating Kelvin probe to monitor the light induced contact potential difference change. We find that the photovoltage (quasi-Fermi level splitting) of all photoelectrodes is increased by the aqueous electrolyte, and strongly depends on the electrochemical potential of the redox couple (TEOA, Na2SO3, KI, K4[Fe(CN)6] in the electrolyte, the back contact, and the light intensity. Electrochemical potentials of the minority carriers at the solid-liquid interface can be estimated by combining the photovoltage data with open circuit potential measurements that yield the quasi-Fermi levels of the majority carriers. This study provides new insight on the factors that affect photochemical charge separation at solid-liquid interfaces.

Figure 1
(Invited) Probing the Atomic and Electronic Structure of Working Energy Materials with x-Ray Spectroscopy
Authors: Dong Chung-Li
Published: July 2022

Improving energy conversion/generation/storage efficiency of energy materials has always been a great challenge. Monitoring the atomic/electronic structures close to interface in many important energy materials, such as nanostructured catalysts, artificially photosynthesizing materials, smart materials, and energy storage devices, is of great importance. Designing such a material with improved performance without understanding its atomic/electronic structures, and their changes under operating conditions, is difficult. Understanding and controlling the interfacial electronic structures of energy materials require in-situ characterizations, of which synchrotron x-ray spectroscopy is the one with many unique features. The last decade has witnessed a golden age of in situ synchrotron x-ray spectroscopy for energy materials. X-ray absorption spectroscopy can be used to determine unoccupied electronic structures while X-ray emission spectroscopy can be utilized to examine occupied electronic structure. The additional use of resonant inelastic X-ray scattering further reveals inter-band d-d excitation or intra-band charge transfer excitation that can reflect the fundamental chemical and physical properties. An emerging technique, scanning transmission x-ray microscopy is a spectro-microscopic approach, providing regional x-ray absorption spectroscopy, is also gearing up for energy science. This presentation will report recent studies and perspectives of the application of in situ/operando synchrotron x-ray spectroscopy to energy materials. Tamkang University (TKU) end-stations constructed at the Taiwan Photon Source (TPS) 45A & 27A beamlines for the x-ray spectroscopic investigation of energy materials will also be introduced.
Space-Resolved Mapping of Catalytic Activity in Electrolysers By Infrared Imaging
Authors: Burdyny Thomas , Iglesias van Montfort Hugo Pieter
Published: July 2022

Novel and established electrochemical reactions come with unwanted heat generation of 30-50% of the inputted power due to cell inefficiencies. Here we seek to use these inefficiencies as a measure of spatial electrochemical activity by taking advantage of the link between heat generation and the activity-dependent transport of electrons and ions. To this end we use data from an infrared camera positioned at the back of a gas-diffusion electrode in an attempt to develop a 'thermal potentiostat' which provides spatial resolution of electrochemical activity. After a proof-of-concept is displayed for the technique, we present several applications of the technology including catalyst screening, spatial-temporal catalyst measurements and the impact of exothermic CO2-hydroxide interactions during CO2 electrolysis. Combined we find that a spatial-thermal potentiostat has numerous uses for both novel and established electrochemical reactions towards the production of renewable fuels and feedstocks.

Figure 1
Single-Atom Photocatalysis: Surface-Defect Engineered TiO2 Anatase As a Tunable Platform for Hosting Co-Catalysts Atoms
Authors: Mohajernia Shiva , Hejazi Sina , Kilian Manuela
Published: July 2022

Single‐atom (SA) or single‐site catalysis (SACs) has over the past years become an increasingly fascinating topic in the catalysis field. SACs have allowed new approaches in heterogeneous catalysis, minimized the use of precious metals, and enabled an unprecedented control over atomistic effects, resulting in improved active sites, and at the same time enabled the design of metal–support interfaces with a high level of structural and chemical control [1,2]. A diverse range of supports and features is known to stabilize isolated metal atoms, notably through pinning at electronic and/or structural defects associated with coordinatively unsaturated sites. However, it is still difficult to create a high density of thermally stable support sites, and hence the fabrication and control of high SA loading remains a challenge [1,2].

In this work, an atomic‐scale defect engineering approach to form and control traps for SA sites as co‐catalyst for photocatalytic H2 generation is described. The control over defect types and density can be monitored by electron paramagnetic resonance spectroscopy (EPR) as the most precise method to study atomic scale defects [3]. Thin sputtered TiO2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA co-catalysts, the TiO2 layers are reduced in Ar/H2 under different conditions (leading to different but defined Ti3+‐Ov surface defects), followed by immersion in a dilute solution containing Pt ion in this study. HAADF‐STEM results show that only on the thin‐film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA‐Pt decoration can enhance the normalized photocatalytic activity of a TiO2 sputtered sample by a great extent in comparison to a conventional nanoparticle‐decorated TiO2 surface. Most interestingly, in the follow up work based on DFT calculations and experimental data we show that Pd single atom outperforms Pt as the most active co-catalyst for photocatalytic H2 evolution [4]. HAADF‐STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt and Pd on TiO2. Importantly, the density of the relevant surface exposed defect centers—thus the density of SA sites, which play the key role in photocatalytic activity—can be precisely optimized.

[1] Sh. Mohajernia et al. Adv. Mater. 2020, 32 (16).

[2] A. Wang, J. Li, and T. Zhang, Nat. Rev. Chem., 2(6).

[3] Sh. Mohajernia et al. J. Mater. Chem. A, 2020, 8(1432)

[4] G. Cha et al. iScience, 2021, 8 (24).

Figure 1
Operando Studies on High-Temperature CO2 Electrolysis to Fuels
Authors: Kamboj Vipin , Ranjan Chinmoy
Published: July 2022

High temperature CO2 electroreduction of one of the most promising technologies for converting CO2 to fuels. Electroreduction can typically result in various reduced products but interms of energy efficiency a electrolytic reduction to CO followed by Fischer Tropsch (along with H2) based conversion to hydrocarbon fuels is most preferred. Nickel-Yttria Stabilized Zirconia cermet (Ni/YSZ) is one of the most common electrodes used in solid oxide fuel cells. Lately, various groups have essentially repurposed the same electrode for CO2 electrolysis. However, it suffers from catalyst degradation and poor activity.

Successful operation of these electrodes requires presence of H2 in the CO2 stream. In presence of hydrogen CO2 undergoes reverere water gas shift reaction leading to production of CO (non electrochemically) in combination with electrochemical water splitting. Using operando Raman and online Mass Spectroscopy we have followed the evolution of catalyst from preatreatment in various atmospheres to its performance under conditions of operation.

The mentioned electrodes were operated at current densities between 100-400 mA/cm2. The operando studies show that Ni active sites oxidize to NiOx in the presence of pure CO2. The poor electronic conductivity of NiO adversely affects the activity of the electrode. The failure is rather drastic at higher current densities. Apart from this, mass spectroscopy confirmed the formation of coke during CO2 electrolysis through Bouduard reaction. The absence of any Raman signal for carbon indicated that the reaction only proceeds to a small extent and the primary deactivation occurs through oxidation of Ni.

Small amounts of H2 (~5%) in the mixture prevented the deactivation, but the reaction seemed to proceed through Reverse Water Gas Shift reaction followed by Water electrolysis. Furthermore, we have explored the performance of Ni(Mx)/YSZ type cathodes for CO2 reduction. The electrode performances were compared using three electrode configuration based measurements. Our results indicate that catalysts development in situ is drastically different for mixed metal oxides often resulting in different type of spatial distribution of the metals compared to the pure Ni/YSZ. Many electrodes show promising behavior in terms of both enhanced activity and catalyst stability.

Figure 1
Tuning the Polarity of Dinitrile-Based Electrolyte Solutions for CO2 Electroreduction on Copper and Copper-Based Catalysts
Authors: Morin Caamano Tatiana , Abu-Lebdeh Yaser , Houache Mohamed , Couillard Martin , Weck Arnaud , Baranova Elena A.
Published: July 2022

Accumulating carbon dioxide (CO2) concentrations in the atmosphere due to anthropogenic sources has become an increasing threat to the environment because of the resulting effects of global warming. It has therefore become imperative to develop and utilize alternative sustainable sources for fuels and feedstock chemicals. CO2 electrochemical reduction (CO2ER) has been identified as a promising process which can convert CO2 to added value chemicals, such as hydrocarbons. In combination with the use of renewable energy resources, the technology has potential to be a net zero carbon process. Commonly, aqueous electrolytes are used for the reaction such as bicarbonate or phosphate-buffered saline solutions. However, these exhibit low CO2 solubilities, which hinders the performance of the reaction by limiting mass transfer. Organic solvent electrolytes possess relatively higher CO2 solubilities. These are also able to suppress the competing hydrogen evolution reaction (HER) due to lowered proton concentrations. Organic nitrile-solvent-based electrolytes, more commonly studied for Li-ion batteries, are known to possess high thermal and electrochemical stability. Furthermore, the polarity and CO2 miscibility can be tuned in dinitrile solvents by variation of the chain length. As such, the effect of chain length was explored on organic dinitrile-based solvent electrolytes for the application of CO2 electroreduction. The selected dinitrile solvents were Adiponitrile (n=4), Suberonitrile (n=6), and Sebaconitrile (n=8), where n indicates the number of methylene groups in the chain. These dinitriles were also compared to Acetonitrile, a commonly used organic mononitrile solvent. Conductivity was first studied as a function of salt concentration and temperature for all solvents. Then, CO2 solubility was evaluated for the different solvents. Finally, electrochemical tests utilizing copper and copper-based bimetallic catalysts were conducted. The catalysts explored consisted of synthesized copper (I) oxide (Cu2O) and copper-silver (CuAg) nanoparticles, obtained through a chemical reduction method in water using sodium borohydride (NaBH4) at ambient conditions. These particles were evaluated against commercial Cu2O and CuAg nanoparticle counterparts. The Cu-based nanoparticles were characterized using XRD, TEM, EDX, and EELS techniques. The obtained results are summarized and discussed.
Solid State Batteries – Chemistry, Electrochemistry and Mechanical Concerns
Authors: Meng Shirley
Published: July 2022

High energy long life rechargeable battery is considered as key enabling technology for deep de-carbonization. Energy storage in the electrochemical form is attractive because of its high efficiency and fast response time. Besides the technological importance, electrochemical devices also provide a unique platform for fundamental and applied materials research since
ion
movement is often accompanied by inherent complex phenomena related to phase changes, electronic structure changes and defect generation. In this talk, I will discuss key chemical, electrochemical and mechanical considerations in all solid state batteries. With recent advances in characterization tools and computational methods, we are able to explore ionic mobility, charge transfer and phase stability in electrode and electrolyte, as well as their interphases in operando, and map out the complex relations in novel solid state materials for next generation energy storage and conversion.
Heterogeneous Damage and Network Evolution in Composite Electrodes of Li-Ion Batteries
Authors: Zhao Kejie , Lin Feng , Liu Yijin
Published: July 2022

We assess the heterogeneous electrochemistry and mechanics in a composite cathode using synchrotron X-ray tomography, machine learning, and microstructure-resolved computational modeling. We visualize the morphological defects at multi-scales ranging from the macroscopic composite, particle ensembles, to individual single particles. Particle fracture and interfacial debonding are identified in a large set of tomographic data. The mechanical failure of active particles is highly heterogeneous. The difference originates from the polarization of the electrolyte potential, various local conducting environments, and thus the non-uniform distribution of the activation energy for the charge transfer reaction. We model the kinetics of intergranular fracture and interfacial degradation to assess the heterogeneous mechanical damage in composite electrodes. We quantify the influence of the mechanical damage on the metrics of battery performance. The mechanical failure disrupts the conduction path of electrons and results in significant polarization and capacity loss in batteries. More interestingly, the interfacial failure may reconstruct the conductive network and redistribute the electrochemical activities that render a dynamic nature of electrochemistry and mechanics evolving over time in the composite electrodes.
(Invited) Modeling the Defect Chemistry, Transport Properties, and Stability of Anti-Perovskite Materials
Authors: Ciucci Francesco
Published: July 2022

Solid-state electrolytes with fast lithium conduction are the core of the all-solid-state Li-battery technology. By substituting the organic electrolyte with a piece of non-flammable ceramic material, we can achieve better safety, higher specific capacity, and a higher energy density. To date, the major bottleneck for this technology is the slow Li diffusion in the solid-state electrolyte and the interfacial incompatibility between the electrolyte and electrodes. To resolve these issues, several families of fast ionic conductors have been developed. Understanding Li diffusion in these materials is essential to the development of novel family fast ionic conductors. To this end, atomistic modeling provides us with a unique tool to obtain comprehensive information on atom motion, which is difficult to access with experimental techniques. In this talk, we showcase our group’s atomistic simulations regarding a novel family of superionic conductors, Li-rich antiperovskites (LiRAPs)

LiRAPs are a promising family of solid electrolytes, which exhibit ionic conductivities above 1 mS/cm at room temperature, among the highest reported values to date. Here, we report on the defect chemistry and the associated lithium transport in Li3OCl, a prototypical LiRAP, using DFT calculations and classical MD simulations [1]. We studied these materials’ phase, interfacial, and voltage stability [2,3] with DFT, showing good agreement with experiments, further proposing low-dimensional superionic antiperovskites [3]. In addition, the interfacial properties were studied for both protonated and fluorinated materials [4]. Analogous simulations were also carried out for Na-rich antiperovskites [5].

Acknowledgments

Support from the Research Grants Council of Hong Kong is gratefully acknowledged.

References

[1] Z Lu, C Chen, ZM Baiyee, X Chen, C Niu, F Ciucci. Defect chemistry and lithium transport in Li3OCl antiperovskite superionic conductors. Physical Chemistry Chemical Physics 17 (48), 32547-32555 (2015)

[2] Z Lu, F Ciucci. Antiperovskite cathodes for lithium batteries. Journal of Material Chemistry A, 6, 5185-5192 (2018)

[3] Z Lu, J Liu, F Ciucci. Superionic conduction in low-dimensional-networked antiperovskites. Energy Storage Materials, 28, 146-152 (2020)

[4] M Effat, J Liu, Z Lu, TH Wan, and F Ciucci. Stability, elastic properties, and the Li transport mechanism of the protonated and fluorinated antiperovskite lithium conductors. ACS Applied Materials and Interfaces, 12, 49, 55011-55022 (2020)

[5] TH Wan, Z Lu, F Ciucci. A first principle study of the phase stability, ion transport and substitution strategy for highly ionic conductive sodium antiperovskite as a solid electrolyte for sodium ion batteries. Journal of Power Sources, 390, 61-70 (2018)
(Invited, Digital Presentation) Heterogeneities at Solid/Solid Interfaces
Authors: Mukherjee Partha P. , Vishnugopi Bairav Sabarish , Naik Kaustubh Girish
Published: July 2022

Solid-state lithium metal batteries hold the potential to enhance the energy density, power density and safety of conventional lithium-ion batteries. Interface stability and performance of solid-state batteries is predicated on the coupled set of electrochemical-mechanical-transport interactions that underlie the solid-solid interfaces within the system. Microstructure of the solid-state cathode dictates the distribution of percolation pathways, reaction kinetics and evolution of distinct internal resistance modes. Morphological response of the anode-electrolyte interface is influenced by various aspects including the presence of defects, grain boundaries and mechanical/transport properties of the solid electrolyte and lithium. In this presentation, the mechanistic role of heterogeneities on the morphological stability of the anode, onset of mechanical/thermal hot spots and electrochemical response of the cathode will be analyzed. The implications of heterogeneous kinetic-transport interactions and chemo-mechanics interplay on the performance and failure modes in solid-state batteries will be delineated.
(Keynote) Enabling High-Rate Lithium Metal Anodes By Tailored Structures and Interfaces
Authors: Wachsman Eric
Published: July 2022

Oxide-based solid-state Li-batteries (SSLiBs) have the potential to be a transformational and intrinsically safe energy storage solution due to their non-flammable ceramic electrolyte that enables the use of high-capacity Li metal anodes and high voltage cathodes for higher energy density over a much wider operating temperature range. However, their progress has been limited due to electrode/electrolyte interfacial issues. In particular for Li-metal anodes concerns over dendrite formation/propagation and the requirement for elevated temperature and high stack pressure are still prevalent. To eliminate these concerns a rational design of tailored structures and interfaces in Li-metal anodes will be presented. In addition, progress toward full cells using these tailored structures and interfaces will be presented.
(Invited) Ion Conduction and Interface Stability of Sulfide Based Solid State Electrolytes – an Atomistic Perspective
Authors: Banerjee Soumik , Dive Aniruddha Mukund
Published: July 2022

All-solid-state batteries are promising in terms of safety as well as high energy density compared to the conventional organic liquid-based lithium batteries. However, the characteristic low ionic conductivity of solid-state electrolytes is a major challenge towards commercialization of solid-state sodium ion batteries. Sulfide-based electrolytes especially in amorphous form have been reported as promising solid electrolytes owing to their relatively high ionic conductivity at room temperature. However, a fundamental understanding of the local structure of these amorphous electrolytes and its subsequent impact on the ion transport could be instrumental in establishing guidelines for designing novel solid electrolytes. In the present work, we utilize first principles and classical atomistic simulations to characterize the local structure and investigate the ion transport in amorphous sulfide electrolytes. We selected sodium thiosilicate [xNa2S – (1-x) SiS2] and sodium thiophosphate [xNa2S – (1-x) P2S5] based electrolytes as a model system wherein we characterized the local structure, ion conduction mechanism and ultimately calculated the ionic conductivity of these electrolytes. We utilized experimental X-ray and neutron scattering data for model validation. Our theoretical calculations provide fundamental insights into ion conduction mechanisms as well as correlate ionic conductivity with electrolyte structure and composition.

Along with ionic conductivity, interfacial stability is extremely important factor influencing the overall performance of solid-state batteries. Interfacial instability with sulfide electrolytes is detrimental to Li-ion transport, leading to poor cycling performance. Inherent thermodynamic instability of sulfide-based solid electrolytes drives the chemical reaction across the interface leading to formation of undesired secondary phases. The secondary phases are formed dynamically during the cycling and therefore a careful investigation into the dynamics at the electrolyte-cathode interfaces is crucial. To generate fundamental understanding of the interface stability, we utilized ab initio molecular dynamics (AIMD) simulations to carefully investigate the dynamics of secondary phase formation across the Li3PS4 | LiCoO2 interfaces. High-resolution microscopy and spectroscopy studies were used to complement the the first principles simulations methods and unravel the interphases formed under different cycling conditions. These calculations provide crucial insights into formation of secondary phases across the interface, which could be leveraged to evaluate possible avenues to inhibit formation of such undesirable secondary phases.
(Invited) Deeply Rechargeable Zinc Anodes for High-Energy Rechargeable Aqueous Batteries
Authors: Liu Nian
Published: July 2022

Zinc-based aqueous batteries are promising alternative to many mainstream battery technologies today, due to the superior safety. However, existing zinc anodes suffer from either poor cycle life or low utilization in both neutral and alkaline aqueous electrolytes. Passivation, dissolution, and hydrogen evolution are three main reasons for irreversibility of zinc anodes in alkaline electrolytes, which limits the rechargeability and usable energy density. In this talk, I will present our recent works on using nanoscale material design to overcome passivation, dissolution, and hydrogen evolution issues of zinc anode, towards a deeply rechargeable zinc-based battery. I will also introduce the battery-gas chromatography quantitative analysis, as well as in situ microscopy methodologies we have developed, to quantify gas evolution side reaction, as well as visualize the reaction on electrodes during operation.
(Invited, Digital Presentation) Multiscale Measurements and Characterization of Thermal Transport in Materials and across Interfaces in Li-Ion Cells
Authors: Jain Ankur
Published: July 2022

Li-ion cells are used universally for energy conversion and storage. Key application areas include electric vehicles, grid energy storage, air/space vehicles and consumer electronics. Overheating of Li-ion cells is a well-known problem, with serious concerns related to thermal runaway and fire. Additionally, Li-ion cells also under-perform at low temperatures, which is a particularly important problem for automotive and space applications. Advances in battery materials are needed to mitigate these concerns and improve the performance and safety of Li-ion cells. This talk will summarize research advances in understanding and optimizing thermal transport in Li-ion cell and battery pack materials. Measurement of thermal conductivity of cylindrical Li-ion cells, indicating the highly anisotropic nature of thermal conduction will be described. This will be followed by discussion of measurement of thermal properties of individual cell materials, such as the separator, as well as thermal contact resistance at the cathode-separator interface. This contact resistance will be shown to play a rate-limiting role in determining overall thermal transport properties of the cell, and is, in particular, responsible for anisotropic thermal conduction. Experiments to mitigate this thermal resistance through molecular bridging at the interface will be described. Good agreement with molecular dynamics simulations will be demonstrated. Challenges associated with practical implementation of such techniques will be discussed. Finally, numerical simulations to understand the nature of thermal transport in battery packs will be described, with the goal of minimizing thermal runaway propagation. These measurements and modeling techniques contribute towards a fundamental understanding of multiscale thermal transport in Li-ion cell materials, and may help optimize and improve thermal performance of practical energy conversion and storage devices.
Planar Anode Supported SOFC Fabricated By Sequential Aqueous Tape Casting, Constrained Cosintering and Screen-Printing
Authors: Parvaix Laura , Lenormand Pascal , Quéré Damien , Rozier Patrick
Published: July 2022

Hydrogen technologies and especially fuel cells, are promising alternatives to achieve a carbon-free energy and an ecofriendly transition [1]. The SOFC technology (Solid Oxide Fuel Cell) is an energy conversion system composed of a stack of a porous cathode, a dense electrolyte and a porous anode working at a temperature in the [600°C – 1000°C] range to obtain ionic conductivity above 10-2 S/cm.

Nowadays, tape-casting is typically used for mass and low-cost manufacturing of supporting half-cell (8YSZ electrolyte and Ni-YSZ anode) and the cathode layer is commonly deposited by screen-printing [2]. In line with the cost reduction problematic, this presentation will describe the development and optimization of a green sequential tape casting process to obtain the anodic half-cell and screen-printing for the cathode. To target green process, aqueous based slurries are used and only non-toxic organic components are selected. The amount of organic components, ceramic powder and water was optimized to obtain slurries with a shear-thinning behavior while managing the powder dispersion stability. The parameters of the drying heat treatment have been optimized based on Thermal Gravimetric Analysis leading to obtain a multilayer flexible green tape without any bubbles or cracks further annealed to eliminate the organics and co-sinter the stack under a porous YSZ load. The flat anodic half-cell with a thin and dense layer of 8YSZ on a thick and porous layer of NiO-YSZ is completed by screen-printing of La2NiO4+
δ (cathode) based ink followed by a consolidation thermal treatment. The characterization using X-ray diffraction, scanning electron microscopy and operando electrochemical tests of the cell allow validating the efficiency of the sequential tape-casting to fabricate via environmentally friendly process and low cost SOFC.

[1] Rissman, J. et al. (2020) ‘Technologies and policies to decarbonize global industry: Review and assessment of mitigation drivers through 2070’, Applied Energy, 266, p. 114848. doi:10.1016/j.apenergy.2020.114848.

[2] Udomsilp, D. et al. (2021) ‘Performance Benchmark of Planar Solid Oxide Cells Based on Material Development and Design.’, Energy Technology, 9. doi:10.1002/ente.202001062.
(Digital Presentation) Ternary Metal Oxide Electrodes Used in Supercapacitor to Improve Emerging Energy Storage
Authors: Zheng Feng , Zhen Qiang , Bashir Sajid , Liu Jingbo Louise
Published: July 2022

Supercapacitors with improved specific capacitance (F g-1), long cycling life, high power (W kg-1), and energy densities (Whkg-1) were fabricated to close the gap between traditional and emerging energy storage materials. We developed responsive supercapacitor electrodes with heterojunctions composed of well-aligned vanadium (V) oxide (V2O5) ribbon arrays and manganese (IV) oxide (MnO2) nanoparticles sphere-network structure. The V2O5 arrays were deposited on the nickel foam substrate using a cost-effective and green hydrothermal chemistry, followed by a MnO2 nano-grafting. The architectural MnO2 modification successfully increased highly reactive interfaces with channels for efficient ion transport. Electrochemical evaluation of this ternary metal oxide system indicated that mesopores and macropores among the MnO2 generated channels that increased electron conduction and shortened ion diffusion pathways. The hybrid electrodes have demonstrated a specific capacitance as high as 788 F g−1 at 5 mV s-1, an improved cyclic steadiness averaged at 92.5 % after 5000 cycles. The charge transfer resistances of these electrodes were lowered to 4.6 Ω and the effective diffusion coefficient of Li+ was 7.90 × 10−9 cm2 s−1. The symmetrical supercapacitor device assembled by the hybrid electrode achieved a high energy density of 138 W h kg-1 at a power density of 450 W kg-1 was achieved and retained at 81.0 W h kg-1 at 9000 W kg-1 after 5000 cycles. The advances in designing nanostructured supercapacitor electrode materials based on these heterojunction arrays enhanced the properties of supercapacitors including specific capacitance, energy density, and cycle stability.

Figure 1