bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) OER Active Phases, Catalytic Mechanism and Reaction Centers of Ni (oxy)Hydroxide with and without Fe Impurities
Authors: Zhu Jing , Dionigi Fabio , Li Wei-Xue , Greeley Jeffrey , Strasser Peter , Zeng Zhenhua
Published: August 2024

Identifying atomic-scale structures of catalytically active phases, catalytic mechanism and reaction centers are crucial for establishing rigorous structure-activity relationship of highly active catalysts and for designing new catalysts with further improved performance. Due to the lack of theoretical guidance and challenges in experimental structural characterization during OER conditions, in-situ structures and stabilities of two (a-Ni(OH)2 and g-NiOOH with water and ion intercalation) out of four (oxy)hydroxide phases (another two are b-Ni(OH)2 and b-NiOOH without water and ion intercalations) remain elusive after at least half a century study, which has hindered the establishment of rigorous structure-activity relationship of Ni (oxy)hydroxides and their derivatives for the OER. As a consequence, it is still unclear regarding which phases should be the hosts and the precursors of choice for highly active catalysts. Here, by combining ab initio molecular dynamics simulation, in-situ wide-angle X-ray scattering, and electrochemical measurements, we provide direct atomic-scale and self-consistent insights into the crystal structure, water and ion intercalation, and stable potential windows of complex a-Ni(OH)2 and g-NiOOH with respect to b-phases. DFT calculations indicate that b-NiOOH and g-NiOOH with Fe impurities have similar OER activity to or even higher OER activity than that of g-NiFe LDH, with a dependence on the Fe coverage on the edges. Current work suggests that both b-NiOOH and g-NiOOH are potential hosts of highly active OER catalysts, which enlarges the phase space for the design of OER catalysts with further improved performance.

We will discuss the implications of the above insights toward understanding of the active phases, reaction centers and catalytic mechanism of NiM and CoM layered double hydroxides. If time permits, we will further review our work our work regarding the promotion effects of non-covalent ligand-oxide interaction in OER and mitigation of RuO6 octahedron distortion by enhanced A-site electronegativity in pyrochlore for acidic water oxidation.

References:

Nature Communications 2020, 11, 2522

Angew. Chem., Int. Ed. 2021, 60, 14446

Journal of Materials Chemistry A 2022, 10, 9419

Nature Communications 2023,14, 997
High Entropy Alloys as High Performance Catalysts for Electrolytic Water Splitting
Authors: Huang Chun–Lung , Lin Yan-Gu , Chiang Chao–Lung , Peng Chun–Kuo , Senthil Raja Duraisamy , Hsieh Cheng–Ting , Chen Yu–An , Chang Shun–Qin , Yeh Yong–Xian , Lu Shih-Yuan
Published: August 2024

Renewable energy driven electrolytic water splitting is a required technology for low-carbon hydrogen production to achieve the goal of net-zero CO2 emission by 2050. This technology also serves as a necessary energy storage route to resolve the intolerable intermittency and unreliability issues of renewable energies. The prevailing of this hydrogen production technology however is restricted by the high cost of electricity. Consequently, developments of cost–effective highly efficient and stable electrocatalysts to drive the electrolytic water splitting reactions are the key. In terms of catalyst developments, mono-component systems are first explored, followed by multi–component systems, taking advantages of possible positive synergy between constituent components. Recently, a new class of multi-component catalyst systems, entropy-stabilized materials, including alloys, oxides, sulfides, phosphides, etc., emerges and is demonstrated promising performances toward electrocatalysis. In light of the variable and flexible element compositions, entropy-stabilized materials provide infinite and enormous potentials for the design of promising electrocatalysts. The key is to maximize the synergy between constituent components. High entropy alloys (HEA), deﬁned as alloys composed of ﬁve or more major metallic elements, have been under intensive and extensive development in past fifteen years for their extraordinary mechanical, magnetic, corrosion, and catalytic properties. Herein, an equi–molar FeCoNiCuMo HEA on nickel foam was developed as a breakthrough catalyst for electrocatalytic water splitting, in terms of both activity and stability, in pH-universal media and in severe industrial operation conditions. Furthermore, a new catalytic phenomenon is discovered. Two different catalytic mechanisms function simultaneously on different constituents of the catalyst, and the synergistic interactions between the two categorical domains leads to catalytic kinetics faster than the theoretical limit set by a single rate-limiting step, Tafel step of the Volmer-Tafel route. A new kinetic model is developed to predict a new theoretical lower limit of Tafel slopes of 15 mV/dec based on a synergistic interaction between the two categorical domains of the high entropy alloy catalyst. This new development proves that the theoretical lower limit of Tafel slope of 30 mV/dec posed for the Volmer-Tafel mechanism functioning on a single component catalyst can be further reduced to 15 mV/dec through synergistic interactions between two categorical domains of a multi-component catalyst. It is demonstrated that high entropy materials, composed of ﬁve or more atomically/molecularly well-mixed major components, are intrinsically promising candidates for realization of quantum leaps in catalytic performances of catalysts.
Statistical Investigation of the Reproducibility of Stack Components in a PEM Water Electrolyzer
Authors: Hoppe Eugen , Janssen Holger , Müller Martin Johannes
Published: August 2024

To achieve homogeneous conditions throughout a single cell of a stack and within a stack and furthermore within several stacks, the components assembled in a stack should be reproducible to achieve a homogeneous performance. To evaluate how reproducible the stack components are, the porous transport layers, the expanded metals sheets, the perforated metal sheets, and the flow field plates from a 5-cell stack were examined.

Eight samples were cut out of each of the 450 cm² layers, and a height profile (area: 10 x 10 mm) was recorded using a laser scan. From the height profile, the roughness values Ra (arithmetic average) and Rz (maximum peak to valley height) could be derived as well as the curvature of the samples (see Figure 1). Figure 1a) shows a contour plot of a perforated metal sheet. There is a height difference of up to 20 µm from the edge to the center of the sample. For the stack assembly this means an initial force is required to flatten the sheet before the actual compression of the stack takes place. Figure 1b) shows the roughness values Ra and Rz. The values vary within the sample (Ra: ± 3.8 µm, Rz: ± 5.7 µm) and throughout the samples (Ra: ± 1.4 µm, Rz: ± 2.5 µm). Further, the thickness of the components was measured, and the variation was calculated. In terms of stacking the components, as done in the stack, the best and worst case were calculated. The aim of this study was to determine input parameters for follow-up tests for the mechanical and electrical characterization of the components as especially the roughness of the components may have a significant impact on the contact resistance.

Figure 1
Diffusion-Bonded Unitized Anode Assemblies for PEM Electrolysis Stacks
Authors: Steele James , Gosselin Sean , Papandrew Alexander B
Published: August 2024

Hydrogen generation via proton exchange membrane (PEM) water electrolysis is in the midst of a technological renaissance aimed at achieving cost parity with steam reforming within the decade. Reaching that plateau will require substantial system cost reductions accompanied by increased performance of the cell stack module. Many proposed improvements to the cell stack draw from the established principles of electrochemical and manufacturing engineering, targeting lower component resistances while lowering part count and enhancing ease of assembly, respectively.

The PEM electrolyzer anode assembly (comprising the porous transport layer (PTL) and the anode flow field) is suited for just such a revision. In practice, the anode PTL is positioned on a metallic bipolar plate that is machined or embossed with a flow field, or the PTL is joined to an assemblage of thin macroporous media that serves as a flow field1. In both cases, the interfacial resistances between the subcomponents of the assembly are non-negligible and are conventionally mitigated by applying noble metal coatings, typically Pt.

In this contribution, we investigate alternatives to conventional assemblies via diffusion bonding. Using thermal treatments, the porous transport layer is joined to the anode flow field, yielding a robust, atomic-scale metallurgical bond. We demonstrate the manufacturing of large-format assemblies in multiple configurations, using either stacked microporous media or grooved plates, meeting tight tolerances for thickness across their span. We also show that the bulk-like character imparted to the assembly obviates the need for antipassivation coatings at the critical interfaces between components, evinced by low series resistance in both ex situ and in situ electrolysis cell tests.

References

(1) Dristy, M. E. Proton Exchange Membrane Electrochemical Cell System. US7270908B2, September 18, 2007.
Hybrid Molecular Layer Deposition of Molybdenum-Aminates as Hydrogen Evolution Reaction Electrocatalysts
Authors: Persson K. Alex , Mattinen Miika , D'Acunto Giulio , Bent Stacey F.
Published: August 2024

The development of high-performance hydrogen evolution reaction (HER) electrocatalysts from noble metal-free materials is critical to achieving cost-effective water splitting and ultimately realizing affordable hydrogen based on renewable energy. Compounds based on earth-abundant transition metals have been the subject of great research interest for this purpose, with metal nitrides gaining recent attention due to their high conductivity and corrosion resistance. Molybdenum nitride-based electrocatalysts have shown particular promise, with many of the best reported activities occurring in composite systems wherein crystalline MoNx domains are embedded in an amorphous N-doped carbon matrix. The present work demonstrates the formation of such uniquely active morphologies in films deposited by organic-inorganic hybrid molecular layer deposition (MLD).

Hybrid MLD is a hybridization of other well-established layer-by-layer deposition techniques – namely atomic layer deposition (used to deposit inorganic films) and purely organic MLD. This family of techniques involves the cyclical exposure of a growth surface to alternating vapor-phase chemical precursors which react in a self-limiting fashion to saturate available surface sites, offering atomic- and molecular-level control over the resulting films. This presentation will introduce the successful development of hybrid MLD deposition procedures for new Mo-aminate materials using Mo(CO)6 as a Mo precursor and various amine precursors, including ethylenediamine, p-phenylenediamine, and tris(2-aminoethyl)amine.

We will describe how the molecular level of control offered by this technique enables tunable variations in film composition and structure, lending unique insights into how the local bonding environment of Mo active sites affects their catalytic properties towards HER. Increased nitrogen loading in the MLD films was shown to decrease the overpotentials required to drive HER in acidic media (0.5 M H2SO4) and improve film stability. Catalysts with N/Mo ratios above 2 demonstrated the best performance, with overpotentials lower than 400 mV at -10 mA/cm2. By incorporating organic components in the MLD films, it was possible to induce desirable morphological changes in the catalytic material – notably including the development of increased active site density – simply through initial exposure to HER testing conditions. The choice of organic precursor affected the rate and extent of these changes through structural effects like crosslinking and crystallinity, which led to more stable catalysts, slowed the rate of morphological changes, and impacted final film structure.
Advancing Green Hydrogen Production with Innovative Materials and Coatings
Authors: DiMeglio John L , Esarey Samuel L , Yang Mengqiao
Published: August 2024

Green hydrogen is a vital solution for reducing greenhouse gas emissions in various sectors of the global economy. As proton exchange membrane (PEM) electrolyzer deployments scale to meet hydrogen production demands, it is critical that raw materials and coatings used in stack designs are carefully engineered for a balance of cost, efficiency, and durability. In this presentation, we will describe technical approaches to assist in the customization of porous transport layer (PTL) components for optimal properties such as mass transport, conductivity, and corrosion resistance. In particular, the design of expanded metal sheets as PTL flow-fields will be described. Computational fluid dynamics (CFD) modeling is used to predict key hydrodynamic properties and inform the engineering of these components. With a specific focus on scalable technologies that can achieve GW/y production volumes, we will demonstrate how PTL assemblies can be economically optimized for performance, under specific PEM electrolyzer form factors and operational conditions.
Coherent Charge Hopping Suppresses Photoexcited Polarons in ErFeO3
Authors: Kim Ye-Jin , Mendes Jocelyn , Michelsen Jonathan , Shin Hyun Jun , Lee Nara , Choi Young Jai , Cushing Scott K
Published: August 2024

We measure how coherent charge hopping competes with and slows small polaron formation. The coupling of photoexcited charge carriers with phonons in the crystal lattice that results in polaron formation causes carrier localization and limits transport to site-to-site hopping. ErFeO3, a rare-earth orthoferrite, is designed where the large rare earth atom frustrates the FeO6 octahedra, reducing the energetic favorability of polaron formation. We compare transient extreme ultraviolet (XUV) measurements with ab initio theory and transport measurements to quantify the polaron formation rate and mobility. Polaron formation occurs within several picoseconds following multiple coherent charge hopping events between neighboring Fe3+–Fe2+ sites. This timescale is more than an order of magnitude longer compared to previously studied materials. The delay in polaron formation is notable because the photoexcited carriers shed excess thermal energy before forming the polaron. To date, polarons have been measured to form instantaneously with the first electron-phonon scattering event. The measured interplay between optical phonons, electron coupling, and on-site lattice deformation emphasizes the importance of dynamic electron correlations for tuning polaron formation in photocatalysts.
A Model Validatory Approach in Determining Solar Panel Tilting Angles and Orientations at the Brikama Environment of The Gambia
Authors: Ayua Tyoyima John , Camara Musa
Published: August 2024

Solar energy demand in The Gambia has got a boost in recent times owning to it cleaner nature and affordability compared to other renewables and by this many people are shifting towards solar PV installation. To optimize the design of any PV system for maximum performance, adequate knowledge of the orientation and tilt angles of the solar panel against the sun radiation received by the solar panel is vital. This paper determines the solar optimal tilt angle and orientation of solar panels in the Brikama environment of The Gambia. This was achieved by comparing a mathematical model results with experimental data collected using a PV module (Model AP-120) manufactured by AstroPower, Inc., Deleware, USA, and single axis tracker technology at the same location and months of the year 2022. The experimental tilt angles obtained range from 29.85-30.14 with an average angle of 29.99 while the mathematical model approach obtained the tilt angle to be 30. By comparing all the values recorded during the experiment, the peak value of power generated by the solar panel was recorded at an angle of 30due South and this proves our techniques in determining the tilted angles with our applied model. The monthly tilt angles of the solar panel, which were averaged from the total months of the year and the average tilt angle in the Brikama environment is 15.5and the solar module should face south during installation for optimization. These results are vital in maximizing solar energy collection from photovoltaic systems.
Value-Added Electrolysis Hydrogen Production Via Methanol Oxidation over a Synergetic Pt1-W Dual-Site Catalyst
Authors: Tsai Meng-Che , Awoke Yohannes Ayele , Su Wei-Nien , Hwang Bing Joe
Published: August 2024

Electrochemical water splitting is a promising way of generating hydrogen for future sustainable green energy source technology options to replace nonrenewable and environmentally pollutant hydrocarbon energy sources. However, due to its high overpotential in oxygen evolution reaction (OER) and low-value product O2, some candidate anodic reactions with low potential should be proposed to replace OER, such as alcohol oxidation. Unlike fuel cell applications, partial oxidation is preferred to achieve high-value products rather than complete oxidation. For this purpose, we design a synergistic effect Pt1-W site on the dual-doped TiO2 support (Ti0.8W0.2NxOy) to catalyze alkaline methanol oxidation and gain 90% selectivity of formate production. Comparing the case of the Pt nanoparticles (69% selectivity of formaldehyde), the Pt single-atom catalyst controls selectivity and enhances the reactivity and stability attributed to the strong catalyst-support interaction. As a result, this work shows a novel strategy for electrochemical hydrogen production at far lower anodic potential by designing a stable and efficient Pt-based single-atom catalyst.
(Invited) Plasmon-Driven Photochemistry for the Synthesis of Metal Nanostructures
Authors: DuChene Joseph S
Published: August 2024

Plasmon-driven photocatalysis with metal nanoparticles holds great promise for initiating and controlling chemical reactions at the nanoscale. One interesting application of plasmonic photochemistry involves the synthesis of metal nanostructures from cationic precursors. Despite more than twenty years of study however, this unique approach to material synthesis remains restricted to just two elements: silver (Ag) and gold (Au). To date, this process is yet to be observed with any other metals. Here, we report the plasmon-driven synthesis of copper (Cu) nanoparticles in aqueous solution via a seed-mediated growth strategy. The plasmonic synthesis is amenable to various Cu precursors, but is highly sensitive to the type of hole scavenger used in the reaction. We also found that the exclusion of oxygen from the system, both in the initial synthesis of Cu seeds and in their subsequent growth into larger nanoparticles, was essential for enabling the plasmon-driven process to proceed. A series of control experiments, supported by photoelectrochemical measurements, were performed to confirm that the growth of Cu nanoparticles occurs via plasmon excitation of the Cu seeds. Overall, our approach offers a unique route to the synthesis of Cu nanoparticles and expands the domain of plasmon-driven photochemistry to a new element.
(Invited) Ultrafast Spectroscopy of Nanostructured Plasmonic and Energy Conversion Materials
Authors: Wiederrecht Gary P.
Published: August 2024

Ultrafast processes that occur upon the absorption of photons by a material frequently play important roles in the efficiency of a desired energy conversion or photocatalytic outcome. For example, energetic carriers produced upon photoexcitation of plasmonic systems can quickly dissipate energy through electron scattering processes on femtosecond timescales, followed by electron-phonon coupling on picosecond timescales. Once the carriers are thermalized, less energy is available to drive a charge separation or photocatalytic process. At the same time, there are number of handles with which to improve the efficiency of photoinduced processes, and ultrafast spectroscopy can be used to characterize that improvement. Nanostructuring, for example, can produce higher efficiency of photocatalytic processes as free charges are more likely to reach a surface following photoexcitation, and local anisotropies at the surface can drive electromagnetic field enhancements and the greater production of “hot” electrons. Hybridization of differing materials is also a powerful handle with which to manipulate or improve charge separation and photocatalytic outcomes. New materials can lead to greater robustness under illumination, as well as lead to changes in dissipation processes. In this talk, I describe recent efforts to characterize novel nanostructures of interest for plasmonics and energy conversion via ultrafast spectroscopy, as well as explore the ultrafast dissipation processes in refractory plasmonic nanomaterials. Particular attention is paid to dissipation of energy to the local environment of the nanoparticles as well as to ultrafast electron scattering processes. Hybrid nanostructures are also explored. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
(Invited) Simultaneous Use of Electric Fields and Plasmonic Carriers for Catalysis
Authors: Jain Prashant K
Published: August 2024

The visible-light excitation of plasmonic nanostructures is now well known to induce catalytic reactions that are not otherwise observed in the dark. One example we have discovered is the conversion of carbon dioxide to hydrocarbons on gold nanoparticles driven by electron–hole pairs generated by plasmonic excitation. However, conversions driven by plasmonically generated carriers can suffer from thermodynamic and efficiency limits. I will describe how such limits can be overcome by simultaneous use of electric fields and plasmonically generated carriers.
Elucidating Photoelectrochemical Corrosion at III-V Semiconductor/Electrolyte Interfaces Using Electrochemical Impedance Spectroscopy
Authors: Hansen Mitchell J. , Steiner Myles A. , Young James L. , Deutsch Todd G , O'Hayre Ryan
Published: August 2024

As the energy transition matures and society looks to mitigate the negative impact of hard-to-decarbonize sectors, the production of green sustainable fuels becomes increasingly important. Photoelectrochemical (PEC) water splitting offers a path towards direct solar-to-hydrogen conversion through its integrated all-in-one design. However, practical device efficiency goals (>20%) necessitate the use of high efficiency III-V semiconductor materials that are unstable in aqueous electrolyte. The rapid degradation of these materials in aqueous media limits their utility to short-lifetime lab-scale devices. Some of the highest efficiency PEC devices to date employ GaInP in the photocathode to drive the hydrogen evolution reaction despite its limited stability. Protective coatings and catalyst layers improve the stability of GaInP photocathodes, but much remains unknown about the exact degradation mechanisms. Here, we use electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis to gain insight into the processes underpinning the degradation of GaInP-based photocathodes in PEC devices.

The EIS technique can monitor charge transfer resistance investigation in PEC devices, but it has had suspect utility for III-V photocathode degradation studies due to rapid material corrosion and slow measurement times. However, the emerging technique of rapid, hybrid EIS measurements provides immense value as a non-destructive and frequency-dependent probe which distinguishes physical processes by their time constants with high resolution. The DRT analysis deconvolutes features of an impedance spectrum without requiring a priori knowledge of the physical processes that contribute to the observed response and ensures unbiased assessment of the data. In this work, we test the effects of Pt nanoparticulate catalyst loading and illumination level on the device impedance and correlate the results to semiconductor corrosion. By varying the cell operating conditions, we perform a robust assignment of the impedance response to physical phenomena. EIS corrosion studies can be complemented by chemical (ICP-MS) and microscopic (optical interferometry) techniques to enhance their correlation. The impedance and material dissolution data provide a better understanding of III-V semiconductor photocorrosion mechanisms.
(Invited) Time-Resolved in Situ Electrochemical SFG Study of Hot Electron Transfer from Metal Electrodes to Adsorbates
Authors: Lian Tianquan
Published: August 2024

here have been recent reports of light enhanced electrocatalysis on metal electrodes, including H2 generation and CO2 reduction. The mechanism of such process remains unclear. One possible mechanism is selective excitation of adsorbate vibrational modes by rapid hot electron transfer and back transfer between the metal and the adsorbate. Although this mechanism has been studied for adsorbate on metal surfaces under vacuum conditions, it is unclear whether similar processes occur under electrochemical conditions and can be tuned by electrochemical bias. Using time-resolved vibrational sum frequency generation (VSFG) spectroscopy, we directly measure hot electron induced vibrational dynamics of adsorbates on metal electrodes. For CO adsorbed on Au electrodes, we show that excitation of the metal leads to the generation of vibrationally excited CO molecules. Detailed analysis reveals that the formation and decay of the excited adsorbates follows the electronic temperature of the electron, indicating the direct coupling of adsorbate vibration modes with hot electrons in the electrodes, likely through ultrafast hot electron transfer and back transfer induced vibrational excitation. This result suggests the possibility of plasmon (or light)-enhanced electrochemistry on metal electrodes. Ongoing studies are systematically examining how the hot electron transfer process depends on the nature of the electrode and applied bias.
(Invited) In Situ Photoelectron Spectroscopy Reveals the Chemical Nature of Semiconductor Surface States
Authors: Favaro Marco
Published: August 2024

The accessible photovoltage of semiconducting photoabsorbers is typically 0.5-1 V below the theoretically achievable values predicted by the Shockley-Queisser limit [1]. Although the reason for this is still not well understood, surface and interface states within the photoabsorbers energy band gap may play a crucial role as they generally induce Fermi level pinning [2]. Within the PEC community, two key elements have been identified for the maximization of the photovoltage in photoelectrodes for water splitting: (i) the passivation of surface defects which is needed to avoid Fermi level pinning, and (ii) the increase of the minority carrier concentration at the interface to improve contact selectivity and optimize carrier extraction [3,4].

To understand the role of surface defects on Fermi level pinning, detailed information on the chemical nature and electronic properties of surface states is needed. Such information is usually obtained with UHV surface science techniques such as XPS, but the photoelectrode surface under UHV conditions has little, if any, relevance to the electrified surface when immersed in the electrolyte. Moreover, recent studies have shown that semiconductor surfaces are not static, but undergo extensive structural and chemical transformations during PEC device operation [5,6]. In this talk, we will show our recent development of state-of-the-art techniques to study the structure and dynamics of semiconductor/water interfaces under practically relevant conditions [7]. The chemical nature of the electronic states for selected semiconductors prepared at the Institute for Solar Fuels has been explored using synchrotron-based resonant, ambient pressure soft and hard X-ray photoelectron spectroscopy (AP-XPS and AP-HAXPES) [6,8-11], and with in situ/operando Raman and photoluminescence spectroscopy. In particular, we will show that it is possible to study photon-induced chemical changes at solid/liquid interfaces using AP-XPS and AP-HAXPES [6,8].

We will conclude this contribution by discussing about future perspectives and technical implementations for multimodal in situ/operando investigations of photoelectrocatalytic processes.

[1] M.T. Mayer. Curr. Opin. Electrochem. 2017, 2, 104.

[2] A. J. Bard et al. J. Am. Chem. Soc. 1980, 102, 3671.

[3] A.G. Scheuermann et al., Nat. Mater. 2016, 15, 99.

[4] M. Schleuning et al., Sustainable Energy Fuels, 2022, 6, 3701.

[5] F.M. Toma et al., Nat.
Commun. 2016, 7, 12012.

[6] M. Favaro et al., J. Phys. Chem. B 2018, 122, 801.

[7] M. Favaro et al., Surf. Sci. 2021, 713, 121903.

[8] M. Favaro et al., J. Phys. D: Appl. Phys. 2021, 54, 164001.

[9] M. Favaro et al., J. Phys. Chem.
C 2019, 123, 8347.

[10] W. Wang et al., J. Am. Chem. Soc. 2022, 144, 17173.

[11] P. Schnell et al., Sol. RRL 2023, 2201104.
(Invited) Porous Crystalline Frameworks as Intrinsic Photocatalytic Materials
Authors: Streater Daniel , Nyakuchena James , Huang Jier
Published: August 2024

Porous crystalline materials such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs) represent a novel class of materials for catalysis due to their inherent porous nature, exceptional thermal and chemical stability, structural flexibility. While many photocatalytic systems based on these materials have been developed in the past decade, a significant gap exists in our understanding of the correlation of photophysical and photocatalytic properties of MOFs/COFs with their structure, which hinders accurate prediction and informed design. We aim to address this challenge using an interdisciplinary approach that combines innovative material design and synthesis, fundamental mechanistic studies, theoretical prediction, and photocatalytic performance evaluation. In this talk, I will discuss our recent progress in developing porous crystalline materials as intrinsic light harvesting materials and heterogenous catalysts for solar fuel generation.
Easy Scalable Solid-State Synthesis of Highly Efficient Synergetic 2D/1D Micro/Nanostructured g-C3N4/MeS (Me=Cd, Mo) Photocatalysts for Organic Dye Degradation and Hydrogen Evolution
Authors: Khan Natalya , Sultanov Fail , Bakenov Zhumabay , Mentbayeva Almagul , Tatykayev Batukhan
Published: August 2024

The global reserves of oil, gas, and coal are acknowledged finite, and their consumption rates are increasing each year [1]. Following Fujishima’s groundbreaking discovery of photocatalytic water splitting using TiO2 electrodes in 1972 [2], photocatalysis technology gained recognition as a promising approach for renewable energy and environmental conservation [3]. Since that pivotal moment, significant advancements have been made in developing preparation methods for highly efficient photocatalysts, predominantly centered on semiconductors like metal oxides and sulfides [4].

In this study, we introduce effective synergistic photocatalysts, that utilize g-C3N4 and MeS (Me=Cd, Mo) semiconductors featuring a 2D/1D micro/nanostructure. Photocatalysts were successfully produced through solid-state method using planetary ball mill, where reaction of MeS formation occurs on the surface of g-C3N4. A comprehensive analysis of the binding energy of electrons of semiconductors was conducted to understand its impact on the photocatalytic activity of the prepared g-C3N4/MeS. The fabricated materials were used in the photodegradation of organic dyes and demonstrated remarkable efficacy. Regarding photocatalytic hydrogen evolution, the g-C3N4/CdS in conjunction with Pt co-catalyst, achieved a hydrogen evolution rate of up to 2254.54 μmol*h⁻¹ *g⁻¹, accompanied by apparent quantum efficiency of 2.0%.

Acknowledgments

This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. АР13068426).

References

[1] E. V. Kondratenko, G. Mul, J. Baltrusaitis, G. O. Larrazábal, J. Pérez-Ramírez, Status and perspectives of CO2 conversion into fuels and chemicals by catalytic, photocatalytic and electrocatalytic processes, Energy & Environmental Science. 6 (2013) 3112–3135. https://doi.org/10.1039/C3EE41272E.

[2] A. Fujishima, K. Honda, Electrochemical Photolysis of Water at a Semiconductor Electrode, Nature. 238 (1972) 37–38. https://doi.org/10.1038/238037a0.

[3] M. Ni, M.K.H. Leung, D.Y.C. Leung, K. Sumathy, A review and recent developments in photocatalytic water-splitting using TiO2 for hydrogen production, Renewable and Sustainable Energy Reviews. 11 (2007) 401–425. https://doi.org/10.1016/j.rser.2005.01.009.

[4] C. Acar, I. Dincer, G.F. Naterer, Review of photocatalytic water-splitting methods for sustainable hydrogen production, International Journal of Energy Research. 40 (2016) 1449–1473. https://doi.org/10.1002/er.3549.
Multifunctional Nanocomposites Synthesized By Solid-Phase Method with High Photocatalytic, Antibacterial, and Fungicidal Activity
Authors: Tugelbay Saparbek , Tatykayev Batukhan , Mucsi Gabor , Shevelkov Andrei , Shalabayev Zhandos , Khan Natalya , Burkitbayev Mukhambetkali
Published: August 2024

An easily scalable technology was developed for the solid-state synthesis of multifunctional hybrid Ag3PO4/AgCl nanocomposites. This innovative approach relies on solution-free (dry) mechanical activation, implemented through successive ion-exchange reactions in a planetary ball mill. The nanosized hybrid structure of the synthesized Ag3PO4/AgCl nanocomposites was substantiated through the utilization of XRD, SEM, TEM, DSC, and UV-visible spectroscopy methods. The investigation also unveiled a synergistic effect between Ag3PO4 and AgCl.

The Ag3PO4/AgCl nanocomposites with a ratio of 75:25 mas. % exhibited the highest and most stable photocatalytic activity under visible light irradiation (λ≥400 nm). The rate constant for the photocatalytic degradation of Methylene Blue (10 mg/L) was found to be two times greater than that observed with Ag3PO4 nanoparticles and four times faster than for AgCl nanoparticles, as illustrated in Figure 1. "In addition, the synthesized nanocomposites remained stable after five cycles of the photocatalytic process, with their activity remaining almost unchanged.

Furthermore, the antimicrobial and fungicidal efficacy of these nanocomposites was assessed using Staphylococcus aureus, Candida albicans, Escherichia coli, Pseudomonas aeruginosa, and Erwinia amylovora test strains. The results of the microbiological tests revealed, that almost all prepared materials were able to suppress pathogenic microorganisms. The conducted study identified these nanocomposites as promising candidates for further detailed and targeted studies concerning their interaction with specific microorganisms.

Figure - 1. (a) Visible spectrum changes of MB during its photodegradation by the Ag3PO4/AgCl -75/25 composite. (b) Photocatalytic degradation profiles of MB over AgCl, Ag3PO4 and Ag3PO4/AgCl catalysts under visible light irradiation. (c) Graphs for determining the kinetics of decomposition of MS under the influence of different catalysts. (d) Photodegradation stability of MB using the Ag3PO4/AgCl – 75/25 catalyst.

Acknowledgments

This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan, grant number АР13068426.

Figure 1
Demonstration of a Robust, Compact Photoelectrochemical (PEC) Hydrogen Generator
Authors: Haber Joel
Published: August 2024

We will report progress on utilizing high-efficiency, dual-junction organo-halide perovskite/Si PV architectures to demonstrate highly integrated, compact, efficient, and robust photoelectrochemical H2 generators. Utilizing size-matched geometric areas for light absorbers, electrocatalysts, and membranes, we demonstrate PEC water splitting devices of 1 cm2 with STH efficiency ≥15% under AM1.5 illumination. Durability data will be reported. Device design specifics including wiring schematics, membrane and catalyst characteristics, and fluid and gas flows will be reported.
Atomic Layer Deposition of Noble Metal Nanoparticles for Electrocatalytic Applications
Authors: Bawab Bilal , Zazpe Raul , Rodriguez Pereira Jhonatan , Sopha Hanna , Macak Jan M.
Published: August 2024

Noble metals such as Pt, Ru, Pd, Ir, etc., have superior performance for various catalytic applications [1]. Due to their scarcity, efforts were being made to reduce the mass/loading or replace these noble metals. Atomic Layer Deposition (ALD) is one among the best technique to facilitate lowering of loading mass on a support of interest [2,3]. Due to the governing surface energy variations between noble metals and support surfaces, the growth initiates as nanoparticles (NP) and with a further increase in ALD cycles the agglomeration among NP’s dominates over the individual NP size increase, thus developing thin films of relatively higher thickness.

For electrocatalytic applications, it is important to choose the right substrates. Among available substrates, carbon papers and titania nanotube layers are best choices considering their physio-chemical properties, availability and low costs incurred.

The uniform decoration of these substrates by NPs of catalysts proved to be highly efficient in electrocatalysis, as shown in our recent papers [3-5].

The presentation will introduce and describe the synthesis of different noble metal NPs by ALD on important substrates. It will also include the corresponding physical and electrochemical characterization and encouraging results obtained in electrocatalysis. References

[1] Huang, Z. F. et al. Advanced Energy Materials vol. 7 (2017) 1700544.

[2] Yoo, J. E. et al. Electrochem. commun. 86, (2018) 6

[3] Anitha, V. C. et al. J. Catal. 365, (2018) 86.

[4] Sitaramanjaneya M. Thalluri & Macak, J. M. Small 19 (2023) 2300974.

[5] B. Bawab et al., Electrochim. Acta 429 (2022) 141044
Aggregation of Homogeneous Porphyrin Catalysts in Organic Electrolyte Broadly Inhibits Electrochemical CO2 Reduction Performance
Authors: Branch Kaitlin L. , Johnson Erin R. , Nichols Eva Megan
Published: August 2024

Metalloporphyrins are widely used as homogeneous electrocatalysts for the production of renewable fuels from abundant feedstocks and sustainable energy. The modularity of porphyrin catalysts has led to the establishment of structure‐function correlations that aid in predicting and optimizing catalytic activity. Although metalloporphyrins are widely known to aggregate due to their planar structure that promotes π–π stacking, it is surprising that the influence of metalloporphyrin aggregation on electrocatalytic performance has not been previously investigated. Herein, we will document the relative aggregation and electrocatalytic activity for CO2 reduction to CO with three structurally related iron meso-phenylporphyrins in commonly used N,N-dimethylformamide (DMF) electrolyte. An inverse dependence of kinetics on catalyst concentration is observed for all three porphyrins based on cyclic voltammetry data. Furthermore, this inhibition extends to bulk electrolysis performance, where up to 75% of the catalyst in a 1 mM solution is inactive compared to in a 0.25 mM solution. This talk will additionally discuss how aggregation is influenced by organic additives, axial ligands, redox state, metal identity, and porphyrin substituents. Overall, this work emphasizes that metalloporphyrins can aggregate severely (even in well-solubilizing organic electrolytes) and that aggregation effects must be considered for optimization of performance and for meaningful catalytic activity comparisons.
(Digital Presentation) New Earth-Abundant Photoelectrocatalyst and Pathway for CO2 Electroreduction
Authors: Galvez Rodrigue Andy , Martinez Perez Octavio , Bergens Steven
Published: August 2024

The rising levels of carbon dioxide (CO2) in the atmosphere is among the most alarming issues in today’s world: harming the environment, health, and economics of all nations on the planet. CO2 capture and its photochemical and/or photoelectrochemical reduction to fuels are promising methodologies to reduce atmospheric CO2. This is a photochemistry, electrochemistry, and catalysis problem. Transition metal complexes that can be tailored to a desired function utilizing a wide range of ligands, play a crucial role in solar fuels chemistry by reducing the activation energy for catalytic CO2 reduction to fuels. In the last decade, Mn-based complexes have sparked a significant interest owing to their abundance in Earth’s crust and lower prices compared to other transition metals. However, a catalyst that operates with high activity and turnover numbers at low overpotential is still required. We report the synthesis, characterization, and activity toward CO2 electrochemical reduction of Mn complexes containing the photoactive, electron-donating 1-imidazole-2,4,6-tri(carbazole-9-yl)-3,5-dicyanobenzene ligand (3CzImIPN). UV-vis and photoluminescence spectra of the Mn complex containing 3CzImIPN will be reported that investigate its photophysical properties under visible light. Cyclic Voltammetry (CV) studies under nitrogen and CO2 will be reported that investigate the electron transfer between the ligand and the Mn centre, as well as the electrochemical reduction of CO2. Evidence will be presented for a new, low overpotential pathway for the electroreduction of CO2 by these types of complexes.

Figure 1
Topologically Enhanced Charged Storage in Complex Particles for Redox-Flow Batteries
Authors: Owhoso Fiki V , Jung Hongju , Kotov Nicholas A. , Kwabi David G.
Published: August 2024

Self-assembled complex nanoparticles are promising charge carriers for energy storage and conversion systems. High specific capacities have been realized in these materials, which has been attributed to various factors such as their high surface area with complex topology and quantum effects caused by nanoscale dimensions. They have nevertheless found limited use in applications beyond metal-ion batteries. We have investigated the deployment of micron-sized FeSe2 particles with nanostructured spikes as charge carriers in redox flow batteries. These so-called “hedgehog” particles (HPs) were found to be dispersible in aqueous media, and displayed shear-thinning rheology in suspension, which facilitated operation in a flow cell. Suspensions of HPs exhibited redox activity around -0.88 V vs Ag/AgCl at pH 14, leading to a 1.0 V open circuit voltage when deployed as the negolyte with ferro/ferricyanide as the posolyte. High current efficiencies (> 97 %) during cycling, and a volumetric capacity of up to 1.4 mol e/L (~ 36.4 Ah/L) were attained. Mechanisms for capacity fade and potential strategies for its mitigation will be discussed.
The Range of Influence across Commercial Glass Fiber Separators on the Cycling of the Zinc Metal Anode
Authors: Hansen Evan J. , Wu Zhenrui , Olfatbakhsh Tina , Milani Abbas , Liu Jian
Published: August 2024

Aqueous zinc-ion batteries (AZIBs) have attracted significant research attention due to their promising potential for large-scale energy storage applications in support of the rapid global growth of renewable wind and solar energy generation. However, challenges associated with the limited cycling life and low energy density of AZIBs persist as the critical limiting factors preventing their practical use in utility-scale energy storage applications [1]. Throughout zinc-ion research working to address these challenges, commercial glass fiber (GF) membranes are often used as the separator in studies investigating cathode, electrolyte, and anode designs [2]. Nevertheless, commercial GF membranes are available with a range of physicochemical properties, and the specific details of the selected membrane are often missing in published studies. In our work, we systematically compare Whatman™ GF separators (GF/A, GF/B, GF/C, GF/D, and GF/F) to assess the influence of the separator’s physicochemical properties (i.e., pore size and thickness) on the cycling life and cell-to-cell variability across multiple trials of Zn|Zn cells. Under constant current cycling, significant differences were observed in the cycling life and cell-to-cell consistency depending on the pore size and thickness of the GF separator [3]. In addition, our use of micro-computed X-ray tomography explores the associations between the separator’s pore size and zinc deposition morphology and provides visual identification of the failure mechanism corresponding with an overpotential collapse. The results of this work clarify the importance of GF separator selection and the separator’s influence to support the improvement of other cell components.

References

[1] L. Ma, M. A. Schroeder, O. Borodin, T. P. Pollard, M. S. Ding, C. Wang, K. Xu, Realizing high zinc reversibility in rechargeable batteries, Nature Energy 5(10) (2020) 743-749.

[2] Y. Zhang, G. Yang, M.L. Lehmann, C. Wu, L. Zhao, T. Saito, Y. Liang, J. Nanda, Y. Yao, Separator Effect on Zinc Electrodeposition Behavior and Its Implication for Zinc Battery Lifetime, Nano Letters (2021).

[3] E. J. Hansen, Z. Wu, T. Olfatbakhsh, A. Milani, J. Liu, The role of glass fiber separators on the cycling of zinc metal anodes, Journal of Membrane Science 688 (2023) 122130.
Mitigation of Negative-Electrode Degradation in Vanadium Redox Flow Batteries
Authors: Perry Mike L. , Darling Robert M.
Published: August 2024

Electrode overpotentials are among the major factors that impact the performance of redox flow batteries (RFBs). However, even though the all-vanadium redox flow battery (VRFB) is the most mature flow-battery chemistry, a recent review article has pointed out that “there is poor agreement between the reported values of kinetic parameters” [1]. Major contributors to this disagreement are the wide variety of carbon materials that are used as electrodes and because the kinetics of both the V(II)/V(III) and V(IV)/V(V) reactions on carbon depend on the electrode pretreatments. The role of surface functional groups and the mechanisms of electron transfer for these reactions is not well understood [1]. There is general agreement that the V(IV)/V(V) kinetics are more facile than the V(II)/V(III) kinetics [2, 3]. Multiple researcher groups have reported electrode overpotential increases with time, and “there is evidence that it occurs mainly on the negative electrode” [1]. Additionally, “reversing the polarity of the VRFB has been suggested as one strategy to recover lost performance but not all investigators have found this strategy effective” [1]. Exposing the V(II)/V(III) electrode to V(IV)/V(V) electrolyte may increase the roughness and oxidize the electrode, which can both improve the activity. It has also been suggested that reversing the polarity may remove impurities, such as copper metal from the negative electrode [4]. More recently, it has been proposed that surface activity may be improved by oxidizing adsorbed V(II) [5]. We hypothesize that V(II)/V(III) electrode degradation on graphitic carbon-fiber electrodes is primarily due to the adsorption of a contaminate that is oxidized when exposed to V(IV)/V(V) electrolyte. We will describe what we suspect is the relevant contaminate species, and we will show the stability of the V(II)/V(III) electrode can be substantially improved by simply removing certain electrolyte-wetted components from the VRFB test apparatus.

References

A. Bourke, D. N. Buckley, et.al., “JES, 170 (2020). 10.1149/1945-7111/acbc99

D. Aaron, T. A. Zawodzinski, et. al., ECS Electrochem. Letters, 2 (2013) 10.1149/2.001303eel

N. Pour, Y. Shao-Horn, et.al., J. of Physical Chemistry C,
119 (2015).10.1021/jp5116806

D. Reynard, H. Girault, et.al., ChemSusChem, 12 (2019). 10.1002/cssc201802895

T. Greese and G. Reichennauer, J. Power Sources, 500 (2021). 10.1016/j/jpowsour.2021.229958