bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Efficiency Electrocatalytic Oxygen Evolution Reaction for Water Splitting Using Vanadium-Based Transition Metal Oxides
Authors: El Issmaeli Youness , Lahrichi Amina , Pollet Bruno Georges
Published: December 2024

The process of water-splitting reactions provides a sustainable method for storing renewable energies by producing hydrogen fuel. Nevertheless, the effectiveness of this procedure is hindered by the oxygen evolution reaction (OER), which is an intricate four-electron oxidation half-reaction. In this study, we report on the synthesis of Vanadium-based Transition Metal Oxide (TM-VOx), a highly active and stable OER catalyst, by a simple hydrothermal method. The electrocatalysts were thoroughly analysed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. When used on nickel (Ni) foam, TM-VOx demonstrated an overpotential of +260 mV at a current density of 10 mA cm-2 in a 1.0 M KOH electrolyte. In addition, the system exhibited remarkable stability for a duration of more than 5 hours without interruption. These findings emphasise the potential of Vanadium-based Transition Metal Oxide materials as highly effective and enduring catalysts for efficient and stable overall water-splitting processes.

Keywords: Vanadium oxide; transition metals; KOH; oxygen evolution reaction; water splitting
Pt/C Catalyst Modified with 14-Membered Macrocyclic Complex for Oxygen Reduction Reaction
Authors: Hu Jiawei , Nagata Shinsuke , Notsu Hideo , Hatakeyama-Sato Kan , Hayakawa Teruaki , Nabae Yuta
Published: December 2024

The modification of Pt-based cathode catalysts with small molecules has emerged as a promising strategy to enhance their durability in the oxygen reduction reaction (ORR) within proton exchange membrane fuel cells (PEMFCs). This study investigates the efficacy of a novel compound, hexaaza macrocyclic ligand (H2HAM), as a modifier anticipated to establish a substantial interaction with the Pt surface. X-ray photoelectron spectroscopy (XPS) analyses, focusing on N1s and Pt4f spectra, reveal a significant electron donation from the ligand to the Pt surface, indicating an improved ligand-Pt interaction. Electrochemical studies demonstrate that the H2HAM-modified Pt/C catalyst maintains its electrochemical active surface area (ECSA) and mass-specific activity more durably compared to a pristine Pt/C catalyst. These findings underscore the potential of H2HAM as an effective modifier for enhancing the durability of Pt-based cathode catalysts in PEMFC applications.

Figure 1
The Effect of SOFC Flow Rate Conditions on the Composition of Lean Oxygen Gas Used in Trigeneration System
Authors: Inagaki Naoyasu , Shimada Iori , Osada Mitsumasa , Takahashi Nobuhide , Fukunaga Hiroshi
Published: December 2024

Solid oxide fuel cell (SOFC) is attracting attention for its high efficiency and low environmental impact. By integrating them into cogeneration systems, which harness the waste heat produced during power generation, significant overall efficiency gains can be achieved. Trigeneration systems (TGS), which extend this concept by incorporating exhaust gases alongside cogeneration, hold promise for reducing overall cost and energy required for the process. In this study, TGS was considered to utilize the exhaust gas from the SOFC cathode as a lean oxygen gas. Conventionally, nitrogen used as lean oxygen gas is obtained through energy-intensive deep cooling separation of air, and the process requires significant cost and energy. They are expected to be reduced by using SOFC exhaust gas to obtain lean oxygen gas. However, employing SOFC in TGS requires consideration of the tradeoff between oxygen concentration and power density. Consequently, this study aims to elucidate the impact of operating SOFC at high oxygen utilization on power generation characteristics. The influence of flow conditions on power generation characteristics was examined through experimental investigations under integral reactor conditions, where air was supplied to the cathode at a small flow rate, and under differential reactor conditions, where gas with a different composition was supplied at a larger flow rate. Additionally, simulations of oxygen concentration distribution within the flow channel were conducted.

Under integral reactor conditions, power generation characteristics of the SOFC exhibited voltage drops in the low current density region at lower flow rates. To investigate variations in oxygen utilization under different flow conditions, concentration and current density distributions within the cell were obtained from numerical analysis using the finite volume method1). A 1-D model was established for analysis, considering mass balance of gas flow in the channel direction. The distribution was calculated by correlating current density with overvoltage and oxygen concentration, as determined from results obtained under differential reactor conditions. The analysis revealed that as flow rates decreased, current density diminished towards the cell outlet, and at lower flow rates, with slight current flow observed near the outlet, indicating little oxygen is consumed there. Consequently, optimizing operating conditions to minimize the portion of the system where oxygen consumption is low are required for effective utilization of SOFC in TGS.

Acknowledgement

This work was supported by F. C. C. Co.

References

1) Y. Inui et al., IEEJ Trans. PE, 123(1), 66 (2003)
Development of Cos-PANI Core-Shell Structure Catalyst for Oxygen Reduction Reaction in Alkaline
Authors: Jae Sang Lee , Jung Won Suk
Published: December 2024

Anion exchange membrane fuel cells(AEMFCs) are a technology that generates electricity through environmentally friendly means by reacting hydrogen and oxygen, producing water as a byproduct. Unlike Polymer Electrolyte Membrane fuel cells(PEMFCs), AEMFCs utilize non-precious metal catalysts in an alkaline environment, promoting more stable reactions. They offer cost-effectiveness and environmentally superior advantages. However, there are still performance shortcomings, necessitating research to enhance the activity of non-precious metal catalysts.

In this study, we synthesized a non-precious metal catalyst using Cobalt sulfide(CoS) and the conductive polymer polyaniline(PANI), and conducted research to enhance its activity. The electrochemical and physicochemical characteristics of the catalyst were observed according to the synthesis temperature conditions of CoS, and the optimization of the synthesis temperature was conducted. Additionally, to protect the active sites, the ratio of the monomer aniline and the oxidant APS was optimized during the polymerization of PANI, resulting in a clustered structure rather than a fiber structure, for encapsulating CoS in a core-shell configuration.
Analysis of Binder Degradation By Measuring Fluorine Emission Rate in PEMFC MEA Made with Speek Membrane and Nafion Binder
Authors: Lee Mihwa , Yoo Donggeun , Park Kwonpil
Published: December 2024

In fuel cell vehicles for large commercial vehicles that require high power, oxygen must be sufficiently transmitted through the binder to the catalyst surface in the catalyst layer of the stack, and the durability of the binder must be high. Although research is actively underway to improve the durability of binders, an in-situ durability evaluation method for binders has not yet been established.

In this study, a study was conducted to accelerate degradation of the catalyst layer using Nafion as a binder with hydrocarbon-based sPEEK membrane and measure the binder degradation rate (FER, Fluorine Emission Rate) in-situ. The binder degradation rate was measured by analyzing the fluorine ion concentration of the condensate while deteriorating the binder in the catalyst layer using the catalytic accelerated degradation protocol. Impedance as in-situ analysis method was measured, and the data was organized using DRT(Distribution of Relaxation Time) and WLR(Warburg-like Response) methods and then compared with FER. It was shown that binder durability can be analyzed by in-situ FER measurement, and it was confirmed that research to increase the binder degradation rate is necessary to improve analysis accuracy.
Plasma-Induced Oxygen Vacancy-Controlled CuOx/N,Se Co-Doped Porous Carbon for Boosted Nitrate Reduction to Green Ammonia
Authors: Maeng Junbeom , Jang Daehee , Ha Jungseub , Kim Won Bae
Published: December 2024

Ammonia has recently emerged as a promising renewable energy carrier owing to its carbon-free nature and high energy density of 4.3 kW h kg−1. However, traditional industrial synthesis of ammonia via the Haber-Bosch process demands high temperatures (400–500°C) and pressures (100–200 atm), resulting in substantial energy consumption and greenhouse gas emissions. The electrochemical nitrate to ammonia reduction reaction (NO3RR) presents a viable alternative to the Haber-Bosch process, although its efficacy is hindered by low reaction performance, particularly due to competitive hydrogen evolution reactions (HER).

In this study, we successfully prepared oxygen vacancy-controlled copper oxide (CuOx) catalysts via a simple plasma treatment. These catalysts were supported on high surface area porous carbon supports co-doped with nitrogen and selenium species to enhance their electrochemical properties. Among these catalysts, the oxygen vacancy-increased CuOx catalyst supported on N,Se co-doped porous carbon (CuOx/NSePC) demonstrated the highest NO3RR performance, achieving a faradaic efficiency (FE) of 87.2% and a yield of 7.9 mg cm-2 h-1 for ammonia production. These results signify significant enhancements in FE and ammonia yield compared to the un-doped or oxygen vacancy-decreased catalysts. The observed high performance can be attributed to an increase in catalytic active sites facilitated by heteroatom doping and weakened N-O bonding strength, enhancing the adsorption of NO3
- ions on modulated oxygen vacancies.

Our findings underscore the importance of co-doping heteroatoms and regulating oxygen vacancies as key factors for enhancing NO3RR catalyst performance, offering valuable insights for effective catalyst design. This work presents a novel approach in the realm of electrochemical nitrate reduction for green ammonia production, providing a foundation for the development of high-efficiency metal oxide-based catalysts and extending their applicability to diverse electrochemical reactions

Figure 1
Numerical Analysis of Patterned Gas Diffusion Layers with Hydrophilic Surface in Proton Exchange Membrane Fuel Cell
Authors: Song Dong Kun , Kim Jung Soo , Lee Seung Heon , Min Gyeong Won , Jung Do Young , Lee Heeyun , Bai Seoung Jai , Cho Gu Young
Published: December 2024

Proton exchange membrane fuel cells (PEMFCs) are electrochemical energy conversion devices which have strengths in efficiency and versatility. Water management is a major research topic for PEMFCs due to their low operating temperatures below 100
℃
. The gas diffusion layers (GDL) play an important role in the water management of PEMFCs. The GDL typically get hydrophobic treatments to remove liquid water and facilitate high performance of PEMFCs. However, Islam et al. experimentally presented that hybrid wettability of GDL can promote liquid water transport by providing pathway for uninterrupted mass transfer.

In this study, the effects of hydrophilic surface on patterned GDL were investigated via three-dimensional multiphase simulation. Vertical and horizontal stripe patterned GDL on serpentine flow field were applied to the cathode side. The performance with and without the hydrophilic surface on each patterned GDL were compared. The mass transfer characteristics of each case, especially convection, were analyzed.
Formation of Atomically Thin Co Layer on Ru Nanoparticles through Surface Limited Redox Replacement of Underpotentially Deposited Zn
Authors: Suyama Kyota , Muramatsu Keisuke , Sugimoto Wataru
Published: December 2024

In order to promote the widespread commercialization of polymer electrolyte fuel cells, highly active electrocatalysts are necessary to reduce the usage of scarce and expensive Pt electrocatalysts. Among various approaches, alloying with non-Pt metals and/or fabricating core-shell structures have been recognized as effective methods to optimize the electronic state of Pt and enhance catalytic activity while reducing Pt loading.1 One ideal catalyst design to maximize Pt utilization involves depositing atomic layers of Pt onto heterogeneous metal surfaces. We have prepared Ru-core@Pt-shell nanostructures by using underpotentially deposited (UPD) Cu on Ru nanostructures and subsequent replacement with Pt atomic layers (Surface Limited Redox Replacement; SLRR).2 In this study, we aimed to control the electronic state of Pt atomic layer on Ru by using a Co-interlayer; i.e. Ru-core@Co-interlayer@Pt-shell nanoparticles.

Since Co cannot be replaced with UPD-Cu, we investigated a synthetic route involving UPD of Zn followed by Co replacement through SLRR. Ru nanoparticles supported on carbon (Ru(np)/C) with particle sizes of approximately 1–3 nm was synthesized according to a previous literature.3 Cyclic voltammetry of Ru(np)/C in an electrolyte solution containing Zn ions was conducted to examine the UPD potential (–0.10 to 0.85 V vs. RHE, 20 mV s–1, pH 11.2). Reduction current was observed near 0 V vs. RHE in the cathodic scan. The deposition potential of Zn in a solution with pH 11.2 was –0.44 V vs. RHE, while the hydrogen evolution potential was 0 V vs. RHE. Therefore, the reduction current most likely originates from UPD of Zn and hydrogen evolution. In the anodic scan, a peak attributed to oxidation of underpotentially deposited Zn was observed near 0.25 V vs. RHE. Subsequently, the Zn deposition amount was calculated by stripping of Zn after maintaining the potential at –0.04 V. The amount corresponds to approximately 40–50% of the ECSA of Ru(np). This result supports the deposition of Zn as atomic layers via UPD. After Zn deposition, Co was deposited through SLRR by immersing the electrode in an aqueous solution containing Co ions. EDS analysis showed a presence of Co and decrease in relative Zn content to Ru compared to Ru(np)/C sample after Zn UPD. Thus, it is suggested that Ru-core@Co-shell nanoparticles were synthesized via Zn UPD.

References

V. Stamenkovic, B. S. Mun, K. J. J. Mayrhofer, P. N. Ross, N. M. Markovic, J. Rossmeisl, J. Greeley and J. K. Nørskov, Angew. Chem. Int. Ed., 45, 2897 (2006).

D. Takimoto, T. Ohnishi, J. Nutariya, Z. Shen, Y. Ayato, D. Mochizuki, A. Demortière, A. Boulineau and W. Sugimoto, J. Catal., 345, 207 (2017).

Y. Takasu, T. Fujiwara, Y. Murakami, K. Sasaki, M. Oguri, T. Asaki and W. Sugimoto, J. Electrochem. Soc., 147, 4421 (2000).

Figure 1
Operando Fluorescence Spectroscopy Setup for Radical Detection during Proton Exchange Membrane Water Electrolysis Operation
Authors: Winkelmann Leonard , De Arghyadeep , Meier Stefan , Wagner Maximilian , Löttert Lukas , Martschin Philipp , Maier Maximilian , Herrmann Yanik , Boehm Thomas , Thiele Simon
Published: December 2024

In a world with an ever-increasing energy demand, efficient and durable energy conversion devices for renewable energy sources are of great importance. Proton exchange membrane water electrolyzers (PEMWEs) are among the industry-established systems for converting electricity into hydrogen as a chemical energy carrier. In these systems, the proton exchange membrane (PEM) has to separate the two evolved gases (H2 and O2). The degradation of this membrane during operation, e.g., membrane thinning, can lead to system failure due to electrical shorts or dangerous explosive gas mixtures of H2 in O2 [1]. Therefore, it is important to gain a detailed understanding of the membrane degradation mechanisms in order to develop suitable mitigation strategies and extend the device lifetime.

One possible cause of ionomer degradation is the evolution of reactive oxygen species (ROS), namely hydroxyl and hydroperoxyl radicals, during WE operation, causing main chain scission and leading to membrane thinning [2]. Due to the very short lifetime of these highly reactive species, direct detection within the PEM is challenging.

However, there is an indirect detection method possible that has already been applied to PEM fuel cells [3]: The membrane is infused with a radical-sensitive fluorescent dye and an optical probe is embedded within this dyed membrane [Fig.1]. This way, a fluorescence signal can be measured upon excitation with a suitable light source. With the membrane being exposed to ROS, the radicals attack the membrane as well as the dye molecules, which can be measured by a change in fluorescence intensity. This setup was adapted for the application in PEMWEs to measure the effect of various operating conditions of the cell on ROS production and, hence, to detect stressors for membrane degradation.

References

[1] Grigoriev, S. A., Dzhus, K. A., Bessarabov, D. G., & Millet, P. (2014). Failure of PEM water electrolysis cells: Case study involving anode dissolution and membrane thinning. International Journal of Hydrogen Energy, 39(35), 20440-20446.

[2] Zhang, Z., Han, Z., Testino, A., & Gubler, L. (2022). Platinum and Cerium-Zirconium Oxide Co-Doped Membrane for Mitigated H2 Crossover and Ionomer Degradation in PEWE. Journal of The Electrochemical Society, 169(10), 104501.

[3] Prabhakaran, V., Arges, C. G., & Ramani, V. (2012). Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy. Proceedings of the National Academy of Sciences, 109(4), 1029-1034.

Figure 1
Study on the Distribution of Platinum within Polymer Membrane during MEA Degradation in PEMFC
Authors: Yoo Donggeun , Oh Sohyeong , Jung Sunggi , Lee Junsub , Park Kwonpil
Published: December 2024

The Pt/C added to the PEMFC polymer membrane serves as a gas barrier, facilitating the generation of water through the hydrogen and oxygen combustion reactions on the Pt surface within the membrane. As water is produced, Pt acts as an antioxidant, humidifying the membrane and preventing radical generation, thus enhancing performance and durability. Pt needs to be closely spaced between particles to act as a radical scavenger, and it has been reported that under different operating and degradation conditions, the size and distribution of Pt within the membrane vary. Therefore, this experiment aimed to observe the movement and distribution changes of Pt/C within the membrane during accelerated degradation.

In this experiment, Pt/C was added to the cathode ionomer layer to manufacture a reinforced membrane with a thickness of 15 μm. The MEA was produced by hot pressing Pt/C electrodes onto the reinforced membrane, with a Pt loading of 0.4 mg/cm2. After assembling the MEA into a cell, chemical durability evaluations of the electrode catalyst, catalyst support, and membrane were conducted. The cross-sections of the MEA before and after degradation were analyzed using SEM and TEM to confirm the distribution of Pt within the membrane.

After chemical degradation of the polymer membrane, Pt/C within the membrane remained stationary, but dissolved/deposited Pt within the electrode layer migrated into the membrane, indicating a closer proximity between Pt/C and Pt. During catalyst and catalyst support degradation, movement of Pt/C within the membrane and changes in its distribution were observed.
Enhanced Electrochemical Hydrogenation of Aromatic Hydrocarbons in Alkaline Electrolytes
Authors: Markunas Brianna , Snyder Joshua David
Published: December 2024

Thermal chemical hydrogenation (TCH) is a key reaction for converting petroleum and biomass feedstocks to value-added fuels and chemicals. Electrochemical hydrogenation (ECH) is a mild alternative where applied potential drives the hydrogenation of hydrocarbons with protons sourced from the aqueous electrolyte near ambient conditions. Lignocellulose is an abundant renewable feedstock comprised of complex phenolic compounds that can be valorized via ECH. Phenol and benzaldehyde are simple model compounds for lignocellulose that have been the focus of recent ECH studies. When both phenol and benzaldehyde are present as reactants, phenol has been shown to act as a proton shuttle, enhancing benzaldehyde ECH rates but with negligible phenol turnover. [1] The study of the role of electrolyte on the ECH of these aromatic hydrocarbons is limited to a few buffer systems (typically acetate, phosphate, or sulfate) and in a pH range of 1-5. However, it well-known that the competing hydrogen evolution reaction (HER) kinetics are slower in base, and that molecules like phenol dissociate within a pH range of 1-14. Thus, a complete understanding of the role of electrolyte pH, especially in alkaline media where slowed HER rates may improve faradaic efficiency of ECH, is desirable.

In this work, we show using cyclic voltammetry and chronoamperometry with product analysis that there are contrasting pH trends between platinum and rhodium for phenol ECH, with the highest ECH rates on platinum at pH 1 and the highest ECH rates on rhodium at pH 10. In-situ electrochemical FTIR and electrochemical impedance spectroscopy reveal that this is the result of differences in hydrogen adsorption kinetics, phenol/H coverage, and competition with HER between the two metals. For phenol ECH on rhodium, we show that pH-driven changes dictate the balance between a hydrogen atom transfer (LH) mechanism and a phenol-mediated proton coupled electron transfer mechanism. We also discuss phenol’s role as a proton shuttle towards benzaldehyde hydrogenation in alkaline pH, near the pka of phenol. With this insight, we show that the unique properties of rhodium and strategic tuning of the acid-base chemistry of phenol and the electrolyte can be utilized to yield elevated ECH rates with enhanced FE through slowed HER.

[1] Sanyal, U., et al., Hydrogen Bonding Enhances the Electrochemical Hydrogenation of Benzaldehyde in the Aqueous Phase. Angew Chem Int Ed
2021, 60 (1), 290–296. https://doi.org/10.1002/anie.202008178.
One Scale to Rule them All – A Unified Redox Scale
Authors: Kienzle Timo , Oppermann Tanja , Radtke Valentin , Krossing Ingo
Published: December 2024

Thermodynamic quantities of single ions, such as the proton activity (i.e. pH values) or single ion Gibbs solvation energies (i.e. redox potential values), are widely used in chemistry and related sciences.[1] Thus, methods for the experimental determination of these values are of great interest. Our work focuses on the experimental determination of Gibbs transfer energies Δtrans
G(i, S1 → S2) of the ion i, between the different solvents S1 and S2, as the central values for the solvent independent, unified acidity scale pHabs
H2O and redox scale E
abs
H2O, and their two-dimensional combination, the Protoelectric Potential Map (PPM).[2] We established an 'ideal' ionic liquid salt bridge (ILSB) setup, using potential measurements between two electrochemical half cells (Fig. 1).[3] In this setup, the electroactive species is dissolved in different solvents, like water or acetonitrile, and the half-cells are connected by an ILSB. 'Ideal' regarding identical diffusion coefficients for both cation and anion of the ionic liquid to minimize liquid junction potentials at the phase boundaries.

Up to now, our research focused on solvents with high permittivity, like water or acetonitrile, utilizing the redox systems Ag+/Ag and Cl2/Cl−.[4] Within this contribution, we present the E
abs
H2O-scale extended by measured transfer energies in low permittivity solvents, like dichloromethane or fluorobenzene, which are not compatible with the previous setup due to the low solubility of the redox systems used. For this application the redox systems Ag+/Ag and Ferrocenium/Ferrocene (Fc+/Fc) were used. In this way, we can include several values measured by cyclic voltammetry.[5] The E
abs
H2O-scale gives the experimental chemist the possibility of a more straightforward synthesis design and the theoretical chemist values to benchmark his calculations.

REFERENCES

P. Hünenberger, M. Reif, Single-ion solvation. Experimental and theoretical approaches to elusive thermodynamic quantities, Royal Society of Chemistry, Cambridge, 2011.

V. Radtke, D. Himmel, K. Pütz, S. K. Goll, I. Krossing, Chem-Eur. J.
2014, 20, 4194.

a) V. Radtke, A. Ermantraut, D. Himmel, T. Koslowski, I. Leito, I. Krossing, Chem. Int. Ed.
2018, 130, 2368; b) A. Ermantraut, V. Radtke, N. Gebel, D. Himmel, T. Koslowski, I. Leito, I. Krossing, Angew. Chem. Int. Ed.
2018, 130, 2372.

a) V. Radtke, N. Gebel, D. Priester, A. Ermantraut, M. Bäuerle, D. Himmel, R. Stroh, T. Koslowski, I. Leito, I. Krossing, Eur. J.
2022, 28, e202200509.; b) V. Radtke, D. Priester, A. Heering, C. Müller, T. Koslowski, I. Leito, I. Krossing, Chem. Eur. J.
2023, 29, e202300609.

I. Krossing, C. Armbruster, M. Sellin, M. Seiler, T. Würz, F. Oesten, M. Schmucker, T. Sterbak, J. Fischer, V. Radtke et al., e-preprint DOI: 10.21203/rs.3.rs-3921217/v1.

Figure 1
Atomic-Scale Direct Observation on Cation Antisite Intermixing and Identification of Charge Conduction Mechanism in p-Type CuBi2O4 for Photocathodes
Authors: Lim Younghwan , Jung Hyun Joon , Park Ki Hyun , Park Chang Hyun , Chung Sung-Yoon
Published: December 2024

Cu-based p-type semiconducting oxides have been investigated for their potential as water-reduction photocathodes in order to enhance energy conversion efficiency in photoelectrochemical cells. Among these oxides, CuBi2O4 has recently gained significant attention as a promising candidate for converting light energy into electrochemical reactions because of its good light absorption property with an adequate bandgap. Despite the importance of identifying the major defect structure to comprehend the electronic conduction behavior, however, no direct experimental analysis has been suggested yet. While the formation of Cu cation vacancies may be discussed as a possible explanation of the p-type conduction behavior, direct evidence regarding the atomic-scale structural and chemical characteristics is still required.

In this research, a combination of advanced characterization techniques is employed to figure out a representative defect structure affecting the optoelectronic properties in CuBi2O4. Cs-corrected scanning transmission electron microscopy (STEM) analysis is conducted to identify a noteworthy occurrence of antisite point defects. Atomic-level energy-dispersive X-ray spectroscopy (EDS) analysis is also employed simultaneously, to clearly show the intermixing of BiCu-CuBi antisite cations as a crucial type of point defect in CuBi2O4. Additionally, a combined result of optical and electrical measurement and density functional theory (DFT) calculations demonstrates the presence of local Cu 3d polaron states in the bandgap. A new type of charge conduction mechanism is created by the hopping of hole-polarons between Cu sites, but it is seriously hindered by the BiCu cations occupying Cu sites. A higher degree of intermixing leads to a greater activation energy and decreased electronic conductivity due to the hindrance of hole-polaron hopping, as evidenced in the Arrhenius plot.

Overall, this research provides valuable insights into the role of antisite defects in CuBi2O4 and their impact on its potential as a photocathode material. The results highlight the significance of the combination of atomic-scale structure analysis and theoretical calculations to identify the possible existence of defects and gain a comprehensive understanding of the electric characteristics in complex oxides for (photo)electrocatalysis. By understanding how antisite defects affect electronic conductivity, various strategies can be developed by controlling the possible defects to optimize not only CuBi2O4 but also other complex oxides for energy-harvesting applications.

Figure 1
Enhanced Design: A User-Friendly 3D-Printed Electrochemical Cell for In Situ Raman Spectroscopy
Authors: Milton Antony Elvin Fernando , Kawashima Kenta , Son Yoon Jun , Chang Woo Je , Wang Ziqing , Marquez Raul A. , Rose Roger F. , Milliron Delia J , Mullins Charles Buddie
Published: December 2024

In energy conversion devices like electrolyzers and batteries, monitoring electrode surfaces during electrochemical processes is crucial for understanding their operation mechanisms. In situ Raman spectroscopy is a promising technique for this purpose, allowing analysis of electrode surface structure, surface species (reaction intermediate species), and localized electrolyte species.1 However, commercially available electrochemical cells designed for in situ Raman spectroscopy are often costly and complex, presenting a bottleneck for widespread use.

To address these issues, some research groups have introduced 3D-printed spectroelectrochemical cells with lower cost and complexity.2,3 However, existing designs typically limit the sample types to specific particles. There is a need for a more versatile, cost-effective, and user-friendly spectroelectrochemical cell that can accommodate a wider range of sample types.

This study presents an innovative spectroelectrochemical cell design capable of accommodating diverse sample types, such as metal foil strips, fluorine-doped tin oxide-coated glass, indium tin oxide-coated glass, and particles. Notably, we feature updates from the previous year's ECS fall conference (i.e., 244th ECS Meeting). Leveraging stereolithography (SLA) 3D printing with resin as the printing material, our cell design prioritizes versatility, affordability, and simplicity. Using the SLA 3D-printed spectroelectrochemical cell, we will demonstrate its practical utility and effectiveness in electrolyzer and battery applications.

References

W. Zheng, Chemistry–Methods, 3, e202200042 (2023).

M. F. dos Santos et al., Anal. Chem., 91, 10386–10389 (2019).

G. D. da Silveira et al., Anal. Chim. Acta, 1141, 57–62 (2021).
Search for Stable Structures of Adsorbed Molecules on Material Surfaces by Bayesian Optimization
Authors: Nogami Shogo , Tamura Tomoyuki , Karasuyama Masayuki
Published: December 2024

Titanium dioxide (TiO2) is one of the most technologically promising oxides with a broad range of catalytic and photocatalytic activities, and first-principles simulations of molecular adsorption onto TiO2 surface have been extensively performed. Our group experimentally reported that the formation of an amorphous structure on the TiO2 surface enhances its catalytic activity, and is investigating the origin of high activity for amorphous surface. From the theoretical point of view, searching for stable adsorption sites on an amorphous surface model based on first-principles calculations need much high computational cost due to many adsorption sites in a large supercell. In this study, to efficiently explore stable adsorption sites on an amorphous surface, we applied Bayesian optimization, a global search method for black-box optimization, and found the most stable adsorption site of a water molecule.

First-principles calculations are performed with SIESTA code [1] with localized basis, using the generalized gradient approximation (GGA) for the exchange-correlation energy functional. The amorphous surface models of TiO2 are generated by quenching a (101) surface model of anatase-type TiO2 crystal containing 162 atoms with first-principles molecular dynamics simulation. Fig. 1 shows one of TiO2 surface models.

The adsorption energy of a molecule adsorbate is defined as

Eads=Etot
(surf+mol)-(Etot
surf+Etot
mol )

Etot
(surf+mol) is the total energy of the surface with a molecule adsorbate, Etot
surf is the total energy of the clean surface, and Etot
mol is the energy of a molecular in a vacuum.

Bayesian optimization is adopted for searching the lowest energy site with fixing TiO2 surface configurations. A Gaussian kernel and an Expected Improvement (EI) for the acquisition function are used.

Absorption energies were calculated on mesh points in the six-dimension space of the atomic positions of the oxygen (x, y, z) and rotational angles. First, we performed Bayesian optimization in the six-dimension space of the position and the angle, but this did not work well due to the discontinuity of the potential surface. Thus, we performed Bayesian optimization in the structural-descriptor space. We adopted the smooth overlap of atomic positions (SOAP) and the radial distribution function (RDF) as structural descriptors. The lowest energy sites were much efficiently found in the descriptor space, and we achieved high search efficiency.

Figure 1
(Invited) Extrinsic and Intrinsic Methods to Increase the Rate Performance of MnO2 Electrodes
Authors: Sugimoto Wataru , Takemura Yuta , Saito Ryota , Hermawan Angga , Muramatsu Keisuke
Published: December 2024

MnO2 is one of the most well studied pseudocapacitive material for aqueous supercapacitors owing to the surface and near surface-confined redox processes. However, due to its poor electronic conductivity, a large amount of conducting additive, needs to be added to achieve high-rate charge storage. Since the conducting additive does not contribute much to the specific capacitance, this leads to decrease in total energy density of the cell in terms of both mass and volume. In addition, polymeric binders are also necessary to fabricate rigid electrode with good contact.

As an alternative to these typical conductive binders and polymer binders, we have studied the possibility of using RuO2 nanosheets as a novel inorganic binder with polymeric properties, high electronic conductivity and excellent pseudocapacitive properties. For example, by adding a small amount of RuO2 nanosheets to particulate MnO2, a large synergetic effect is observed leading to a high utilization of MnO2 pseudocapacitance.1 The optimized amount of RuO2 in the composite was 13 wt%, which is much lower than the amount generally used for conductive carbon additives. The size of nanosheet binders also affects the properties of the electrode. Using MnO2 nanosheets and RuO2 nanosheets with different lateral sizes, it has been shown that larger sized nanosheets affords better conductive binder properties through a better electronic conduction network structure.

Asides from using conductive binders, heterogeneous doping can increase the intrinsic conductivity of MnO2. We have shown that Ir-doped Birnessite shows faster redox behavior than pristine MnO2 and this enhanced kinetics are reflected on the exfoliated nanosheets. These properties can be discussed based on the electronic interaction between Mn and Ir.

The pseudocapacitive performance of MnO2 can also be manipulated by inducing cationic defects in Birnessite. Low temperature annealed MnO2 with higher number of defects shows higher specific capacitance at low rate, albeit at the loss of high-rate performance. This trade-off is discussed based grain-boundary resistance dominating the rate performance.

Acknowledgments

This work was supported in part by ISHIFUKU Metal Industry Co., Ltd. and a Japan Science and Technology Agency Program on Open Innovation Platform with Enterprises,

Research Institute and Academia (JST OPERA JPMJOP1843).

References:

Saito, Y. Sato, D. Takimoto, S. Hideshima, W. Sugimoto, Electrochemistry, 88(3), 107 (2020).

Saito, H. Tanaka, K. Teshima, D. Takimoto, S. Hideshima, W. Sugimoto, Inorg
.
Chem., 61, 4566 (2022).
(Invited) Application of Structured Electrodes for Photoelectrochemisry Under Dark
Authors: Fukushima Tomohiro , Itatani Masaki , Murakoshi Kei
Published: December 2024

We employed well-defined nano- and micro-structured electrodes for water electrolysis. Based on the observation of bubble generation induced by hydrogen and oxygen evolution reactions, the catalytic activity of the structured electrodes was characterized, suggesting the contribution of molecule polaritons to enhancing water reduction and oxidation, respectively. The potential application of this approach is discussed for photoelectrochemistry under dark conditions.
(Invited) Photocatalytic Semiconductor Membrane with Directional Flow of Charge Carriers
Authors: Kamat Prashant V
Published: December 2024

Designing a hybrid semiconductor nanocrystal:cocatalyst assembly in a polymer membrane is an effective approach to direct the flow of photogenerated charge carriers. Directing such vectorial charge transfer in a photocatalytic membrane is useful in suppressing undesired side reactions (e.g. reoxidation of a reduced product) and facilitating product separation. We have now made use of the ion exchange property of a cation exchange membrane, Nafion, to embed semiconductor nanoparticles (e.g., CdS, AgInS2). Bipolar membrane (BPM) are also employed to load the semiconductor photocatalyst on one side and metal electrocatalyst on the other side of the membrane. The photocatalytic semiconductor/metal membrane when inserted between the two compartments of an H-cell, serves the dual purpose of generating hydrogen while separating the oxidation and reduction products. The talk will focus on preparing photocatalytic membrane and their effectiveness in solar fuel production and some of the key factors that dictate the efficiency of solar fuel generation.
Surface and Defect Modulation via Flame Technique for Efficient Photoelectrochemical Water-Splitting
Authors: Tan Runfa , Jeong YooJae , Cho In Sun
Published: December 2024

The conversion of solar energy into chemical fuel via photoelectrochemical (PEC) water splitting shows great promise for solving the energy crisis, achieving carbon neutrality, and a sustainable future. Iron (Fe)-based materials have attracted tremendous attention from various light absorber materials due to their earth abundance, high light absorption, and robust PEC stability under harsh conditions[1]. However, diverse shortcomings, such as the short hole diffusion length, severe bulk/interface recombination, and sluggish water oxidation kinetics, limit the photocurrent generation for achieving high solar-to-hydrogen efficiency[2,3]. In particular, the high-temperature annealing requirement necessitates suitable synthesis and activation strategies to awaken their PEC activity.

In this talk, we present a novel high-temperature flame technique to activate two Fe-based model photoanodes, i.e., zinc ferrite (ZnFe2O4, ZFO) and hematite (Fe2O3). The flame-activated ZFO (just a few tens of seconds) exhibits an enhanced charge collection ability and enriched active sites compared to the non-activated ZFO. These improvements are attributed to the high-temperature induced grain growth, enhanced grain connection, and rich defect formation caused by the fuel-rich flame environment[4]. On the other hand, a unique textured and mesoporous hematite (tm-hematite) photoanode can be synthesized via the same flame technique combining solution chemistry. The resultant tm-hematite exhibited enlarged surface area, enhanced charge transport, and transfer properties. We show that the unique mesoporous morphology, dominated (110) plane, and rich Ti dopant concentration on grain surface are responsible for the enhanced PEC activity. Notably, the tm-hematite showed greatly enhanced photocurrent density (3.1 mA/cm2 at 1.23 V vs the reversible hydrogen electrode, RHE) compared to the conventional nanorod hematite (~1.4 mA/cm2 at 1.23 VRHE) under 1 sun illumination. The flame-activated ferrite photoanodes demonstrated excellent PEC stability for 50 hours, even without additional coating/treatments. Our flame technique shows extraordinary potential for synthesizing high-efficiency ferrite-based photoelectrodes and puts a step forward to achieving the goal of sustainable energy and environment future.

Keywords: Photoelectrochemical water splitting, Ferrites, Flame treatment, defect control, mesoporous structure, charge collection, photocurrent density, stability

References

[1] R. Tan, A. Sivanantham, B. J. Rani, Y. J. Jeong, I. S. Cho, Coord. Chem. Rev.
2023, 494, 215362.

[2] I. S. Cho, M. Logar, C. H. Lee, L. Cai, F. B. Prinz, X. Zheng, Nano Lett.
2014, 14, 24.

[3] I. S. Cho, H. S. Han, M. Logar, J. Park, X. Zheng, Adv. Energy Mater.
2016, 6, 1501840.

[4] R. Tan, Y. J. Jeong, Q. Li, M. Kang, I. S. Cho, J. Adv. Ceram.
2023, 12(3): 612-624.

Figure 1
(Invited) Innovation in Heterogeneous Catalysis: Constructive Interference at the Interface
Authors: Leddy Johna
Published: December 2024

Reaction rates are increased by better catalysts and by introduction of energy as heat or pressure. In electrochemical systems, energy is introduced as electrical potential that drives electron transfer across the electrode solution interface. In sonochemical systems, energy is imparted to bulk solvents by ultrasound that generates cavitation bubbles; as cavitation bubbles collapses extremes of temperature (> 5000 C) and pressure (> 1000 atm) are induced in a narrow domain about the collapsed bubble.

By coupling sonochemistry and electrochemistry, extremes of pressure are deposited at the electrode solution interface to increase electron transfer rates and to remove passivating layers such as oxides from the electrode surface.

The system is built as a thin layer electrochemical cell where sonicator and electrode are separated by about the wavelength of the ultrasound, on the order of a 1 cm. When properly aligned, constructive interference builds pressure at the electrode solution interface at a rate of about 1 J (mole s)-1. The oscillators operate in the range of 40 kHz, with little parasitic loss.

Constructive interference in thin layer sonoelectrochemical cells substantially increases rates of O2 reduction and alcohol electrolysis.

The financial support of the National Science Foundation (NSF CHE-1309366) is acknowledged.

References

Chester G. Duda, Brenna Parke, and Johna Leddy, “Thin Layer Sonoelectrochemistry:Impact on Slow Heterogeneous Electron Transfer,” Electrochimica Acta (2023) 468 143118 https://doi.org/10.1016/j.electacta.2023.143118.

Daniel L. Parr IV, Chester G. Duda, and Johna Leddy, “Why Sonochemistry in a Thin Layer? Constructive Interference," J. Physical Chemistry C (2023) 127(25) 12184-12193, https://doi.org/10.1021/acs.jpcc.3c00804.

Daniel L. Parr IV and Johna Leddy, “To Configure Thin Layer Sonoelectrochemical Experiments,” Journal of the Electrochemical Society (2021) 168(6) 066524, https://iopscience.iop.org/article/10.1149/1945-7111/ac0861.

J. Leddy, C. G. Duda, J. Lyon, and W. J. Leddy III, “Thin layer sonochemistry and sonoelectrochemistry devices and methods,” US Patent 10,300,453, May 2019, Assignee: Johna Leddy, https://patents.google.com/patent/US10300453.
(Invited) Tunable Electronic Charge Transport in Hexammineruthenium Hexacyanometallate Double-Complex Crystals and Their Prussian Blue Analog Thermal Decomposition Products
Authors: Robinson Donald "Donny" A , Sagar Srikrishna , Ghotbi Maryam , Shivanna Mohana , Smeaton Michelle A , Ferguson Andrew J , Wheeler Lance M , Jungjohann Katherine L , Babuena Perla B , Talin Albert Alec
Published: December 2024

The complex ions, hexammineruthenium [Ru(NH3)6]2+/3+ and hexacyanoferrate [Fe(CN)6]3-/4- are well known redox couples with reversible interfacial electron transfer kinetics, with rate constants that are too fast to measure with conventional electrochemical methods. This presentation will show that when mixed together, they form insoluble double-complex Ax[Ru(NH3)6][Fe(CN)6] crystals with rhombahedral symmetry, where A is a cationic species and 0≤x≤2. The analogous reaction of [Ru(NH3)6]2+/3+ with [Ru(CN)6]3-/4- produces Ax[Ru(NH3)6][Ru(CN)6] crystals. These materials thus provide an excellent model system to link outer-sphere molecular charge transfer theory with solid-state electronic charge transport. Thermal decomposition at mild temperatures removes ammine ligands and transforms these crystals into nanopolycrystalline/amorphous Prussian blue analogs (PBAs) that retain the macroscopic geometry of the double-complex crystals. This presentation will introduce the crystal structures, spectroscopic characterizations, and electronic charge transport measurements of the double-complex single-crystals and their PBA decomposition products prepared at different oxidation states, including mixed valence forms. Efforts to develop physical models based on density functional theory and Marcus theory to elucidate charge transport in double-complex crystals and PBAs will also be discussed, as well as methods to fabricate neuromorphic devices based on the tunable conductivity of the double-complex crystals and PBAs.
(Invited) Active Learning Strategies for Teaching Electrochemical Energy Conversion and Storage: Insights from Science Clubs
Authors: Marquez Raul A. , Kalokowski Emma , Espinosa Michael , Ramos-Sanchez Victor Hugo , Rodriguez Luis Carlos , Valenzuela de la Rosa Fernando , Mullins C Buddie
Published: December 2024

Electrochemistry is rapidly growing, yet its crucial role in emerging industries and research is not sufficiently mirrored in the curriculum of US and Mexican universities. While undergraduate students are briefly exposed to basic electrochemistry concepts within general and physical chemistry courses, dedicated electrochemistry education is often reserved for graduate programs. Furthermore, teaching electrochemistry is challenging as it is a multifaceted subject encompassing concepts from various disciplines. Despite this complexity, electrochemistry equips students with invaluable skills in analytical chemistry, experimental design, instrumental analysis, and device engineering. Recognizing the need for a skilled workforce to meet the demands of emerging industries, it is imperative to reinvigorate electrochemistry education and introduce it at the early undergraduate level to foster interest and deeper engagement.

To bridge this educational gap, we have developed a science workshop focusing on teaching electrochemical energy conversion and storage concepts to high school and early undergraduate students. As part of Clubes de Ciencia MX, a Mexican initiative promoting science and engineering summer workshops, this unique experience has utilized active learning strategies to teach and encourage electrochemistry for two consecutive years. The workshop covers five fundamental areas (Figure 1): electrochemistry basics, water electrolysis, electrocatalysis, fuel cells, and battery technology. By integrating short lectures, group discussions, and interactive learning through experiments, games, and project-based activities, we strive to ignite students' passion for electrochemistry. We have also conducted assessments to examine the workshop's effectiveness and influence on students' understanding of the role of electrochemistry in climate empowerment and sustainability. This unique experience aims to captivate and inspire early-career students, nurturing the next generation of scientists and engineers who will revolutionize our world.

Figure 1