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Abdel-Aziz AB, Heakal FET, El Nashar RM, Ghayad IM. Green synthesis and characterization of binary, ternary, and quaternary Ti/MMO anodes for chlorine and oxygen evolution reactions. Sci Rep 2024; 14:9821. [PMID: 38684728 PMCID: PMC11058822 DOI: 10.1038/s41598-024-59595-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Accepted: 04/12/2024] [Indexed: 05/02/2024] Open
Abstract
Dimensionally stable anodes of titanium (Ti) metal coated with mixed metal oxides (MMO) are widely used in several electrochemical applications, especially chloro-alkali electrolysis. Herein, we deposited MMO coatings on Ti substrates in different compositions, namely, (60%RuO2-40%TiO2), (60%RuO2-30%TiO2-10%IrO2), and (60%RuO2-20%TiO2-15%IrO2-5%Ta2O5), where RuO2 has the same percentage ratio in all coatings. The aim was to use these electrodes for chlorine evolution reaction (CER) and oxygen evolution reaction (OER) applications. Electrochemical characterization of the coated samples was performed to identify the best Ti/MMO electrodes with the highest efficiencies among the various prepared combinations. The role of IrO2 and Ta2O5 in enhancing corrosion resistance and electrochemical efficacy was up for debate. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were exploited to determine the surface morphology, chemical composition, crystallinity, surface composition, and chemical states of the acquired coatings. The differential scanning calorimetry (DSC) method was used to evaluate the apparent activation energy ( E a ) of the deposited MMO. Additionally, the electrochemical performance of our designed coatings was scrutinized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), a current on-off test, a CV stability test (ST), and an accelerated stability test (AST). Furthermore, linear sweep voltammetry (LSV) was incorporated to assess the catalytic efficacy of the prepared anodes toward the CER in a brine solution of pH 2 and the OER in 1 M H2SO4. It became clear that the CER and OER incurred almost the same potential value (1.1 V) on both Ti/RuO2-TiO2 and Ti/RuO2-TiO2-IrO2 electrodes. However, on the Ti/RuO2-TiO2-IrO2-Ta2O5 anode, there was a 0.2 V potential difference between the CER occurring at 1.1 V and the OER happening at 1.3 V.
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Affiliation(s)
- A B Abdel-Aziz
- October High Institute for Engineering & Technology, Giza, 12596, Egypt
| | - F El-Taib Heakal
- Chemistry Department, Faculty of Science, Cairo University, Giza, 12613, Egypt.
| | - R M El Nashar
- Chemistry Department, Faculty of Science, Cairo University, Giza, 12613, Egypt
| | - I M Ghayad
- Central Metallurgical Research and Development Institute (CMRDI), Cairo, 12422, Egypt.
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Choi S, Choi WI, Lee JS, Lee CH, Balamurugan M, Schwarz AD, Choi ZS, Randriamahazaka H, Nam KT. A Reflection on Sustainable Anode Materials for Electrochemical Chloride Oxidation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2300429. [PMID: 36897816 DOI: 10.1002/adma.202300429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 02/28/2023] [Indexed: 06/18/2023]
Abstract
Chloride oxidation is a key industrial electrochemical process in chlorine-based chemical production and water treatment. Over the past few decades, dimensionally stable anodes (DSAs) consisting of RuO2 - and IrO2 -based mixed-metal oxides have been successfully commercialized in the electrochemical chloride oxidation industry. For a sustainable supply of anode materials, considerable efforts both from the scientific and industrial aspects for developing earth-abundant-metal-based electrocatalysts have been made. This review first describes the history of commercial DSA fabrication and strategies to improve their efficiency and stability. Important features related to the electrocatalytic performance for chloride oxidation and reaction mechanism are then summarized. From the perspective of sustainability, recent progress in the design and fabrication of noble-metal-free anode materials, as well as methods for evaluating the industrialization of novel electrocatalysts, are highlighted. Finally, future directions for developing highly efficient and stable electrocatalysts for industrial chloride oxidation are proposed.
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Affiliation(s)
- Seungwoo Choi
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea
- Soft Foundry, Seoul National University, Seoul, 08826, South Korea
| | - Won Il Choi
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea
| | - Jun-Seo Lee
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea
| | - Chang Hyun Lee
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea
| | - Mani Balamurugan
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea
| | - Andrew D Schwarz
- Milton Hill Business and Technology Centre, Infineum, Abingdon, OX13 6BB, UK
| | - Zung Sun Choi
- Infineum Singapore LLP, Singapore, 098632, Singapore
| | | | - Ki Tae Nam
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea
- Soft Foundry, Seoul National University, Seoul, 08826, South Korea
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Shin S, Wi TU, Kong TH, Park C, Lee H, Jeong J, Lee E, Yoon S, Kim TH, Lee HW, Kwon Y, Song HK. Selectively Enhanced Electrocatalytic Oxygen Evolution within Nanoscopic Channels Fitting a Specific Reaction Intermediate for Seawater Splitting. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2206918. [PMID: 36567426 DOI: 10.1002/smll.202206918] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/04/2022] [Indexed: 06/17/2023]
Abstract
Abundant availability of seawater grants economic and resource-rich benefits to water electrolysis technology requiring high-purity water if undesired reactions such as chlorine evolution reaction (CER) competitive to oxygen evolution reaction (OER) are suppressed. Inspired by a conceptual computational work suggesting that OER is kinetically improved via a double activation within 7 Å-gap nanochannels, RuO2 catalysts are realized to have nanoscopic channels at 7, 11, and 14 Å gap in average (dgap ), and preferential activity improvement of OER over CER in seawater by using nanochanneled RuO2 is demonstrated. When the channels are developed to have 7 Å gap, the OER current is maximized with the overpotential required for triggering OER minimized. The gap value guaranteeing the highest OER activity is identical to the value expected from the computational work. The improved OER activity significantly increases the selectivity of OER over CER in seawater since the double activation by the 7 Å-nanoconfined environments to allow an OER intermediate (*OOH) to be doubly anchored to Ru and O active sites does not work on the CER intermediate (*Cl). Successful operation of direct seawater electrolysis with improved hydrogen production is demonstrated by employing the 7 Å-nanochanneled RuO2 as the OER electrocatalyst.
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Affiliation(s)
- Seokmin Shin
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Tae-Ung Wi
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, 77005, USA
| | - Tae-Hoon Kong
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Chanhyun Park
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Hojeong Lee
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Jihong Jeong
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Eunryeol Lee
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Subhin Yoon
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Tae-Hee Kim
- Ulsan Advanced Energy Technology R&D Center, KIER, Ulsan, 44776, Korea
| | - Hyun-Wook Lee
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Youngkook Kwon
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
| | - Hyun-Kon Song
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea
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Abstract
Fuel cells (FCs), water electrolyzers (WEs), unitized regenerative fuel cells (URFCs), and metal-air batteries (MABs) are among the emerging electrochemical technologies for energy storage, fuel (H2), oxidant (O2), and clean energy production. Their commercial applications are hindered by the low oxygen reduction reaction/oxygen evolution reaction (ORR/OER) bifunctional activity (for URFCs and MABs), OER selectivity (brine electrolysis in seawater and Martian environments), and high cost of the benchmark electrocatalysts (OER: RuO2, IrO2 and ORR: Pt/C) which affects the performance and affordability of the devices. Low-cost electrocatalysts with highly symmetric ORR/OER bifunctional activity and high OER selectivity are crucial for large-scale FC, WE, URFC, and MAB application. Recent studies have revealed that tuning the structure of pyrochlore oxides provides a pathway to enhancing OER and ORR activity over a wide range of pH. Pyrochlore oxides commonly contain a cubic A2B2O7-x structure with two types of tetrahedrally coordinated O atoms containing (1) A-O-A and (2) A-O-B types with a cationic radii mismatch of rA/rB > 1.5 and propensity toward oxygen vacancy formation. The variety of pyrochlore oxides and their tunable properties make them attractive for a wide spectrum of applications. Among all the metal oxides, Ru-based pyrochlores (e.g., Pb2Ru2O7-x) exhibit the best bifunctional oxygen electrocatalytic activity, i.e., low bifunctionality index (BI), in alkaline medium. Furthermore, pyrochlores exhibit high OER selectivity in brine electrolytes due to the presence of surface oxygen vacancies, making them suitable for space applications (brine electrolysis on Mars) and coastal hydrogen generation. Their bifunctional activity and selectivity can be further amplified by (1) substituting "A" and "B" sites of pyrochlores (AA'BB'O7-x), (2) tuning metal oxidation states of A and B by varying synthesis conditions, and (3) modulating oxygen vacancy concentration, each of which yield favorable structural and electronic variations. In recent years, research on the synthesis and understanding of pyrochlores has significantly enhanced their viability, offering a new horizon in the quest for economical and active electrocatalysts. However, an account that focuses on critical developments in this field is still lacking.In this Account, we focus on the recent development of a variety of pyrochlore electrocatalysts to understand intrinsic structure-activity-selectivity-stability relationships in these materials. Recent developments and applications of pyrochlore-based electrocatalysts are discussed under the following headings: (1) modulation of crystal and electronic structure of pyrochlores, (2) structure-activity-stability relationships of different pyrochlores for OER and ORR, (3) development of OER-selective pyrochlores for brine electrolysis, and (4) the application of pyrochlores in electrochemical devices. Finally, we highlight some unaddressed issues such as the precise identification of active sites, which can be addressed in the future through advanced in situ and ex situ characterization techniques coupled with the density functional theory-based analyses. This Account provides foundational understanding to guide the comprehensive development of highly active, selective, stable and low-cost structurally engineered pyrochlores for high performance electrochemical devices.
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Affiliation(s)
- Pralay Gayen
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Sulay Saha
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Vijay Ramani
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
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Gomer A, Bredow T. Effect of Doping on Rutile TiO 2 Surface Stability and Crystal Shapes. Chemistry 2022; 11:e202200077. [PMID: 35642133 PMCID: PMC9156812 DOI: 10.1002/open.202200077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/14/2022] [Indexed: 11/06/2022]
Abstract
Transition-metal-(TM-)doped TiO2 has been considered as promising electrode material for the oxygen evolution reaction (OER). OER activity is expected to depend on the coordination of the surface atoms. In this study, we theoretically investigate the stability of low-index surfaces of TM-doped rutile, (110), (100), (101) and (001), with 50 % of the Ti atoms substituted by Sc, Y, V, Nb or Ta. For Sc and Y, we also consider models with O vacancies providing the most stable oxidation state of Sc and Y. Surface energies are calculated with DFT(+U). Based on the Gibbs-Wulff theorem, the shape of the single crystals is predicted. It is observed that p-doping leads to spontaneous oxygen loss and O vacancies cause surface reconstruction. The Wulff shapes of n-doped TiO2 have smaller contributions of the (110) facet and, for Nb and Ta, larger contributions of other facets. Given the higher coordinative unsaturation of the TM atoms in the latter, a higher catalytic activity is expected.
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Affiliation(s)
- Anna Gomer
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Thomas Bredow
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
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High Selectivity Electrocatalysts for Oxygen Evolution Reaction and Anti-Chlorine Corrosion Strategies in Seawater Splitting. Catalysts 2022. [DOI: 10.3390/catal12030261] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Seawater is one of the most abundant and clean hydrogen atom resources on our planet, so hydrogen production from seawater splitting has notable advantages. Direct electrolysis of seawater would not be in competition with growing demands for pure water. Using green electricity generated from renewable sources (e.g., solar, tidal, and wind energies), the direct electrolytic splitting of seawater into hydrogen and oxygen is a potentially attractive technology under the framework of carbon-neutral energy production. High selectivity and efficiency, as well as stable electrocatalysts, are prerequisites to facilitate the practical applications of seawater splitting. Even though the oxygen evolution reaction (OER) is thermodynamically favorable, the most desirable reaction process, the four-electron reaction, exhibits a high energy barrier. Furthermore, due to the presence of a high concentration of chloride ions (Cl−) in seawater, chlorine evolution reactions involving two electrons are more competitive. Therefore, intensive research efforts have been devoted to optimizing the design and construction of highly efficient and anticorrosive OER electrocatalysts. Based on this, in this review, we summarize the progress of recent research in advanced electrocatalysts for seawater splitting, with an emphasis on their remarkable OER selectivity and distinguished anti-chlorine corrosion performance, including the recent progress in seawater OER electrocatalysts with their corresponding optimized strategies. The future perspectives for the development of seawater-splitting electrocatalysts are also demonstrated.
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Hong JC, Kuo TC, Yang GL, Hsieh CT, Shen MH, Chao TH, Lu Q, Cheng MJ. Atomistic Insights into Cl –-Triggered Highly Selective Ethylene Electrochemical Oxidation to Epoxide on RuO 2: Unexpected Role of the In Situ Generated Intermediate to Achieve Active Site Isolation. ACS Catal 2021. [DOI: 10.1021/acscatal.1c03574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Jia-Cheng Hong
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Tung-Chun Kuo
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Guo-Lin Yang
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Chi-Tien Hsieh
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Min-Hsiu Shen
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Tzu-Hsuan Chao
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Qi Lu
- State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 10084, China
| | - Mu-Jeng Cheng
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
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High-performance AEM unitized regenerative fuel cell using Pt-pyrochlore as bifunctional oxygen electrocatalyst. Proc Natl Acad Sci U S A 2021; 118:2107205118. [PMID: 34593643 DOI: 10.1073/pnas.2107205118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2021] [Indexed: 11/18/2022] Open
Abstract
The performance of fixed-gas unitized regenerative fuel cells (FG-URFCs) are limited by the bifunctional activity of the oxygen electrocatalyst. It is essential to have a good bifunctional oxygen electrocatalyst which can exhibit high activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this regard, Pt-Pb2Ru2O7-x is synthesized by depositing Pt on Pb2Ru2O7-x wherein Pt individually exhibits high ORR while Pb2Ru2O7-x shows high OER and moderate ORR activity. Pt-Pb2Ru2O7-x exhibits higher OER (η@10mAcm-2 = 0.25 ± 0.01 V) and ORR (η@-3mAcm-2 = -0.31 ± 0.02 V) activity in comparison to benchmark OER (IrO2, η@10mAcm-2 = 0.35 ± 0.02 V) and ORR (Pt/C, η@-3mAcm-2 = -0.33 ± 0.02 V) electrocatalysts, respectively. Pt-Pb2Ru2O7-x shows a lower bifunctionality index (η@10mAcm-2, OER - η@-3mAcm-2, ORR) of 0.56 V with more symmetric OER-ORR activity profile than both Pt (>1.0 V) and Pb2Ru2O7-x (0.69 V) making it more useful for the AEM (anion exchange membrane) URFC or metal-air battery applications. FG-URFC tested with Pt-Pb2Ru2O7-x and Pt/C as bifunctional oxygen electrocatalyst and bifunctional hydrogen electrocatalyst, respectively, yields a mass-specific current density of 715 ± 11 A/gcat -1 at 1.8 V and 56 ± 2 A/gcat -1 at 0.9 V under electrolyzer mode and fuel-cell mode, respectively. The FG-URFC shows a round-trip efficiency of 75% at 0.1 A/cm-2, underlying improvement in AEM FG-URFC electrocatalyst design.
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Saha S, Kishor K, Pala RGS. Climbing with support: scaling the volcano relationship through support–electrocatalyst interactions in electrodeposited RuO 2 for the oxygen evolution reaction. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00375e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The interfacial charge transfer and support-induced electrocatalyst faceting in thin catalysts enable ‘climbing up’ the volcano map for OER electrocatalysts. The conductivity of the support determines the OER activity of thick catalysts.
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Affiliation(s)
- Sulay Saha
- Department of Chemical Engineering
- Indian Institute of Technology
- Kanpur
- India
| | - Koshal Kishor
- Department of Chemical Engineering
- Indian Institute of Technology
- Kanpur
- India
- S. N. Patel Institute of Technology & Research Centre
| | - Raj Ganesh S. Pala
- Department of Chemical Engineering
- Indian Institute of Technology
- Kanpur
- India
- Materials Science Programme
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Abstract
NASA's current mandate is to land humans on Mars by 2033. Here, we demonstrate an approach to produce ultrapure H2 and O2 from liquid-phase Martian regolithic brine at ∼-36 °C. Utilizing a Pb2Ru2O7-δ pyrochlore O2-evolution electrocatalyst and a Pt/C H2-evolution electrocatalyst, we demonstrate a brine electrolyzer with >25× the O2 production rate of the Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) from NASA's Mars 2020 mission for the same input power under Martian terrestrial conditions. Given the Phoenix lander's observation of an active water cycle on Mars and the extensive presence of perchlorate salts that depress water's freezing point to ∼-60 °C, our approach provides a unique pathway to life-support and fuel production for future human missions to Mars.
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Exner KS. Design criteria for the competing chlorine and oxygen evolution reactions: avoid the OCl adsorbate to enhance chlorine selectivity. Phys Chem Chem Phys 2020; 22:22451-22458. [PMID: 32996945 DOI: 10.1039/d0cp03667f] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The formation of gaseous chlorine within chlor-alkali electrolysis is accompanied by a selectivity problem, as the evolution of gaseous oxygen constitutes a detrimental side reaction in the same potential range. As such, the development of electrode materials with high selectivity toward the chlorine evolution reaction is of particular importance to the chemical industry. Insight into the elementary reaction steps is ultimately required to comprehend chlorine selectivity on a molecular level. Commonly, linear scaling relationships are analyzed by the construction of a volcano plot, using the binding energy of oxygen, ΔEO, as a descriptor in the analysis. The present article reinvestigates the selectivity problem of the competing chlorine and oxygen evolution reactions by applying a different strategy compared to previous literature studies. On the one hand, a unifying material-screening framework that, besides binding energies, also includes the applied overpotential, kinetics, and the electrochemical-step symmetry index is used to comprehend trends in this selectivity issue for transition-metal oxide-based electrodes. On the other hand, the free-energy difference between the adsorbed oxygen and adsorbed hydroxide, ΔG2, rather than ΔEO is used as a descriptor in the analysis. It is demonstrated that the formation of the OCl adsorbate within the chlorine evolution reaction inherently limits chlorine selectivity, whereas, in the optimum case, the formation of the Cl intermediate can result in significantly higher chlorine selectivity. This finding is used to derive the design criteria for highly selective chlorine evolution electrocatalysts, which can be used in the future to search for potential electrode compositions by material-screening techniques.
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Affiliation(s)
- Kai S Exner
- Sofia University, Faculty of Chemistry and Pharmacy, Department of Physical Chemistry, 1 James Bourchier Avenue, Sofia 1164, Bulgaria.
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