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Journal ArticleDOI: 10.1007/S41918-020-00084-1

Understanding the Mechanism of the Oxygen Evolution Reaction with Consideration of Spin

05 Mar 2021-Vol. 4, Iss: 1, pp 136-145
Abstract: The oxygen evolution reaction (OER) with its intractably high overpotentials is the rate-limiting step in many devices, including rechargeable metal–air batteries, water electrolysis systems and solar fuel devices. Correspondingly, spin state transitions from spin singlet OH–/H2O reactants to spin triplet O2 product have not yet received enough attention. In view of this, this article will discuss electron behaviours during OER by taking into consideration of spin attribute. The main conclusion is that, regardless of the possible adopted mechanisms (the adsorbate evolution mechanism or the lattice oxygen mechanism), the underlying rationale of OER is that three in four electrons being extracted from adsorbates should be in the same spin direction before O=O formation, superimposing high requirements on the spin structure of electrocatalysts. Therefore, upon fully understanding of the OER mechanism with considerations of spin, the awareness of the coupling between spin, charge, orbital and lattice parameters is necessary in the optimization of geometric and electronic structures in transition metal systems. Based on this, this article will discuss the possible dependency of OER efficiency on the electrocatalyst spin configuration, and the relevance of well-recognized factors with spin, including the crystal field, coordination, oxidation, bonding, the eg electron number, conductivity and magnetism. It is hoped that this article will clarify the underlying physics of OER to provide rational guidance for more effective design of energy conversion electrocatalysts.

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Topics: Spin states (55%), Singlet state (53%)

9 results found

Journal ArticleDOI: 10.1021/ACSAMI.1C11101
Weimo Li1, Lusi Zhao1, Ce Wang1, Xiaofeng Lu1  +2 moreInstitutions (3)
Abstract: The development of highly efficient and cheap electrocatalysts for the oxygen evolution reaction (OER) is highly desirable in typical water-splitting electrolyzers to achieve renewable energy production, yet it still remains a huge challenge. Herein, we have presented a simple procedure to construct a new nanofibrous hybrid structure with the interface connecting the surface of CeO2 and CoO as a high-performance electrocatalyst toward the OER through an electrospinning-calcination-reduction process. The resultant CeO2-CoO nanofibers exhibit excellent electrocatalytic properties with a small overpotential of 296 mV at 10 mA cm-2 for the OER, which is superior to many previously reported nonprecious metal-based and commercial RuO2 catalysts. Furthermore, the prepared CeO2-CoO nanofibers display remarkable long-term stability, which can be maintained for 130 h with nearly no attenuation of OER activity in an alkaline electrolyte. A combined experimental and theoretical investigation reveals that the excellent OER properties of CeO2-CoO nanofibers are due to the unique interfacial architecture between CeO2 and CoO, where abundant oxygen vacancies can be generated due to the incomplete matching of atomic positions of two parts, leading to the formation of many low-coordinated Co sites with high OER catalytic activity. This research provides a practical and promising opportunity for the application of heterostructured nonprecious metal oxide catalysts for high-efficiency electrochemical water oxidation.

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Topics: Electrocatalyst (52%), Oxygen evolution (51%)

1 Citations

Open accessJournal ArticleDOI: 10.1063/5.0061703
Yuan Cao1, Linfeng Gao1, Zhenhai Lai2, Cheng Wang1  +3 moreInstitutions (2)
Abstract: Designing efficient oxygen evolution reaction (OER) electrocatalysts is essential for numerous sustainable energy conversion technologies. An obstacle that impedes the development of OER electrocatalysts is the insufficient emphasis on the spin attribution of electrons. Recently, the different spin configuration of reactants and products in the OER has been recognized as the factor that slows down the reaction kinetics. In this work, Mn substitution was introduced to LaCoO3, which brought about lattice expansion and reduced crystalline field splitting energy. This led to the increase in the effective magnetic moment, which triggers the transfer of Co3+ from low to higher spin states. Thus, the hybridization of Co eg and O 2p states across the Fermi level was strengthened. Specifically, with 25 at. % Mn substitution, LaCoO3 transits from a semiconductor to a half-metal, which benefits the spin-oriented electronic transport and resultantly promotes the OER. This method paves the way for the construction of spin pathways in catalysts.

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Topics: Spin states (50%)

Journal ArticleDOI: 10.1002/CSSC.202101898
Yanying Liu, Daojin Zhou1, Tianyin Deng, Guangli He  +4 moreInstitutions (2)
27 Oct 2021-Chemsuschem
Abstract: The development of a low-cost and high-efficiency oxygen evolution reaction (OER) catalyst is essential to meet the future industrial demand for hydrogen production by electrochemical water splitting. Given the limited reserves of noble metals and many competitive applications in environmental protection, new energy, and chemical industries, many studies have focused on exploring new and efficient non-noble metal catalytic systems, improving the understanding of the OER mechanism of non-noble metal surfaces, and designing electrocatalysts with higher activity than traditional noble metals. This Review summarizes the research progress of anode OER catalysts for hydrogen production by electrochemical water splitting in recent years, for noble metal and non-noble metal catalysts, where non-noble metal catalysts are highlighted. The categories are as follows: (1) Transition metal-based compounds, including transition metal-based oxides, transition metal-based layered hydroxides, and transition metal-based sulfides, phosphides, selenides, borides, carbides, and nitrides. Transition metal-based oxides can also be divided into perovskite, spinel, amorphous, rock-salt-type, and lithium oxides according to their different structures. (2) Carbonaceous materials and their composite materials with transition metals. (3) Transition metal-based metal-organic frameworks and their derivatives. Finally, the challenges and future development of the OER process of water splitting are discussed.

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Topics: Noble metal (57%), Water splitting (54%), Transition metal (53%) ... show more


56 results found

Journal ArticleDOI: 10.1039/C4CS00448E
Xiaoxin Zou1, Yu Zhang2Institutions (2)
Abstract: Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

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Topics: Water splitting (59%), Hydrogen economy (56%), Hydrogen production (54%) ... show more

3,353 Citations

Journal ArticleDOI: 10.1126/SCIENCE.1212858
09 Dec 2011-Science
Abstract: The efficiency of many energy storage technologies, such as rechargeable metal-air batteries and hydrogen production from water splitting, is limited by the slow kinetics of the oxygen evolution reaction (OER). We found that Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3–δ (BSCF) catalyzes the OER with intrinsic activity that is at least an order of magnitude higher than that of the state-of-the-art iridium oxide catalyst in alkaline media. The high activity of BSCF was predicted from a design principle established by systematic examination of more than 10 transition metal oxides, which showed that the intrinsic OER activity exhibits a volcano-shaped dependence on the occupancy of the 3d electron with an e g symmetry of surface transition metal cations in an oxide. The peak OER activity was predicted to be at an e g occupancy close to unity, with high covalency of transition metal–oxygen bonds.

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Topics: Oxide (54%), Oxygen evolution (53%), Perovskite (structure) (52%) ... show more

3,135 Citations

Journal ArticleDOI: 10.1002/CCTC.201000397
11 Jul 2011-Chemcatchem
Abstract: Trends in electrocatalytic activity of the oxygen evolution reaction (OER) are investigated on the basis of a large database of HO* and HOO* adsorption energies on oxide surfaces. The theoretical overpotential was calculated by applying standard density functional theory in combination with the computational standard hydrogen electrode (SHE) model. We showed that by the discovery of a universal scaling relation between the adsorption energies of HOO* vs HO*, it is possible to analyze the reaction free energy diagrams of all the oxides in a general way. This gave rise to an activity volcano that was the same for a wide variety of oxide catalyst materials and a universal descriptor for the oxygen evolution activity, which suggests a fundamental limitation on the maximum oxygen evolution activity of planar oxide catalysts.

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Topics: Oxygen evolution (57%), Oxide (57%), Overpotential (53%) ... show more

2,154 Citations

Journal ArticleDOI: 10.1038/NCHEM.1069
01 Jul 2011-Nature Chemistry
Abstract: The prohibitive cost and scarcity of the noble-metal catalysts needed for catalysing the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries limit the commercialization of these clean-energy technologies. Identifying a catalyst design principle that links material properties to the catalytic activity can accelerate the search for highly active and abundant transition-metal-oxide catalysts to replace platinum. Here, we demonstrate that the ORR activity for oxide catalysts primarily correlates to σ-orbital (e(g)) occupation and the extent of B-site transition-metal-oxygen covalency, which serves as a secondary activity descriptor. Our findings reflect the critical influences of the σ orbital and metal-oxygen covalency on the competition between O(2)(2-)/OH(-) displacement and OH(-) regeneration on surface transition-metal ions as the rate-limiting steps of the ORR, and thus highlight the importance of electronic structure in controlling oxide catalytic activity.

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Topics: Catalysis (52%), Oxide (51%)

1,875 Citations

Journal ArticleDOI: 10.1021/ACSCATAL.6B02479
02 Nov 2016-ACS Catalysis
Abstract: Increasing demand for finding eco-friendly and everlasting energy sources is now totally depending on fuel cell technology. Though it is an eco-friendly way of producing energy for the urgent requirements, it needs to be improved to make it cheaper and more eco-friendly. Although there are several types of fuel cells, the hydrogen (H2) and oxygen (O2) fuel cell is the one with zero carbon emission and water as the only byproduct. However, supplying fuels in the purest form (at least the H2) is essential to ensure higher life cycles and less decay in cell efficiency. The current large-scale H2 production is largely dependent on steam reforming of fossil fuels, which generates CO2 along with H2 and the source of which is going to be depleted. As an alternate, electrolysis of water has been given greater attention than the steam reforming. The reasons are as follows: the very high purity of the H2 produced, the abundant source, no need for high-temperature, high-pressure reactors, and so on. In earlier days,...

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Topics: Steam reforming (62%), Photoelectrolysis (57%), Energy source (56%) ... show more

1,238 Citations

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