Oxygen evolution in spin-sensitive pathways
TL;DR: In this paper, the effects of spin in OER based on the recent advances and summarize the recently proposed mechanisms of the OER in spin-sensitive pathways under the lattice oxygen oxidation mechanism, the interaction of two M−O entity mechanism, and the adsorbate evolution mechanism.
About: This article is published in Current Opinion in Electrochemistry.The article was published on 2021-12-01. It has received 22 citations till now. The article focuses on the topics: Oxygen evolution.
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TL;DR: In this paper , the authors survey recent advances in using a magnetic field in different electrochemical applications organized by the effect of the generated forces on fundamental electrochemical principles and focus on how the magnetic field leads to the observed results.
Abstract: Abstract Developing new strategies to advance the fundamental understanding of electrochemistry is crucial to mitigating multiple contemporary technological challenges. In this regard, magnetoelectrochemistry offers many strategic advantages in controlling and understanding electrochemical reactions that might be tricky to regulate in conventional electrochemical fields. However, the topic is highly interdisciplinary, combining concepts from electrochemistry, hydrodynamics, and magnetism with experimental outcomes that are sometimes unexpected. In this Review, we survey recent advances in using a magnetic field in different electrochemical applications organized by the effect of the generated forces on fundamental electrochemical principles and focus on how the magnetic field leads to the observed results. Finally, we discuss the challenges that remain to be addressed to establish robust applications capable of meeting present needs.
27 citations
TL;DR: In this article , a strategy to regulate the electron density distribution by integrating NiFe layered double hydroxides (NiFe−LDH) nanosheets with Co3O4 nanowires to construct the NiFe•LDH/Co3O 4 p−n heterojunction supported on nickel foam for electrocatalytic oxygen evolution reaction (OER) is proposed.
Abstract: Here, a strategy to regulate the electron density distribution by integrating NiFe layered double hydroxides (NiFe‐LDH) nanosheets with Co3O4 nanowires to construct the NiFe‐LDH/Co3O4 p‐n heterojunction supported on nickel foam (NiFe‐LDH/Co3O4/NF) for electrocatalytic oxygen evolution reaction (OER) is proposed. The p‐n heterojunction can induce the charge redistribution in the heterogeneous interface to reach Fermi level alignment, thus modifying the adsorption free energy of *OOH and improving the intrinsic activity of the catalyst. As a result, NiFe‐LDH/Co3O4/NF exhibits outstanding OER performance with a low overpotential of 274 mV at a current density of 50 mA cm−2 and long‐time stability over 90 h. Moreover, NF can serve as a magnetic core that induces the exchange bias effect between the magnetic substrate and the active species under the action of the magnetic field, resulting in decreased magnetoresistance and weakened scattering of spin electrons, which further lowers the OER overpotential by 25 mV @ 50 mA cm−2 under a 10 000 G magnetic field. This work provides a new perspective on the design of p‐n heterojunction catalysts and a deeper understanding of the magnetic field‐enhanced electrocatalytic reactions.
22 citations
TL;DR: In this article , the spin-regulated inner-sphere ET can be enhanced by both exchange and superexchange interactions in [Fe4S4]-dependent SAM enzymes, which enable the efficient cleavage of the S −C(γ) or S−C5' bond of SAM.
Abstract: Electron transfer (ET) is a fundamental process in transition-metal-dependent metalloenzymes. In these enzymes, the spin-spin interactions within the same metal center and/or between different metal sites can play a pivotal role in the catalytic cycle and reactivity. This Perspective highlights that the exchange and/or superexchange interactions can intrinsically modulate the inner-sphere and long-range electron transfer, thus controlling the mechanism and activity of metalloenzymes. For mixed-valence diiron oxygenases, the spin-regulated inner-sphere ET can be dictated by exchange interactions, leading to efficient O-O bond activations. Likewise, the spin-regulated inner-sphere ET can be enhanced by both exchange and superexchange interactions in [Fe4S4]-dependent SAM enzymes, which enable the efficient cleavage of the S─C(γ) or S─C5' bond of SAM. In addition to inner-sphere ET, superexchange interactions may modulate the long-range ET between metalloenzymes. We anticipate that the exchange and superexchange enhanced reactivity could be applicable in other important metalloenzymes, such as Photosystem II and nitrogenases.
7 citations
TL;DR: In this paper , the authors comprehensively discuss all possible effects of magnetic fields on the oxygen evolution reaction (OER), including the magnetohydrodynamic effect in the electrolyte, the spin selectivity and spin alignment in the interface, and the spin alignment and magnetothermal effects in electrocatalysts.
Abstract: Overall water splitting efficiency is retarded by the kinetics of the sluggish oxygen evolution reaction (OER). Recently, increasing attention has been attracted to the spin-sensitive nature of the OER and the utility of magnetic fields (MF) for enhancing catalytic performance. Actually, MF should have performed even better, if we had a correct and comprehensive understanding of its possible effects on the whole OER system. Herein, we comprehensively discuss all possible effects of MF on the OER, including the magnetohydrodynamic effect in the electrolyte, the spin selectivity effect in the interface, and the spin alignment and magnetothermal effects in electrocatalysts. We point out that the MF type/setup and the magnetism of electrocatalysts are the two primary determinants for the real effectiveness of MF. This perspective is expected to provide instructive guidance for utilizing magnetic fields to improve the performance of water splitting as well as other spin-sensitive energy conversion reactions.
4 citations
TL;DR: In this article , the chiral induced spin selectivity (CISS) effect was used to improve the efficiency of top-performing catalysts through control over reaction intermediate spin alignment during electrolysis, and the improvement in OER manifested as an increase in Faradaic efficiency, decrease in reaction overpotential, and change in the rate determining step for chiral nanocatalysts over compositionally analogous achiral nano-graphs.
Abstract: Continual progress in technologies that rely on water splitting are often hampered by the slow kinetics associated with the oxygen evolution reaction (OER). Here, we show that the efficiency of top-performing catalysts can be improved, beyond typical thermodynamic considerations, through control over reaction intermediate spin alignment during electrolysis. Spin alignment is achieved using the chiral induced spin selectivity (CISS) effect and the improvement in OER manifests as an increase in Faradaic efficiency, decrease in reaction overpotential, and change in the rate determining step for chiral nanocatalysts over compositionally analogous achiral nanocatalysts. These studies illustrate that a defined spatial orientation of the nanocatalysts is not necessary to exhibit spin selectivity and therefore represent a viable platform for employing the transformative role of chirality in other reaction pathways and processes.
4 citations
References
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TL;DR: 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 eg symmetry of surface transition metal cations in an oxide.
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.
3,876 citations
TL;DR: In this paper, density functional theory (DFT) calculations are performed to analyze the electrochemical water-splitting process producing molecular oxygen (O 2 ) and hydrogen (H 2 ).
2,063 citations
TL;DR: Using in situ 18O isotope labelling mass spectrometry, direct experimental evidence is provided that the O2 generated during the OER on some highly active oxides can come from lattice oxygen.
Abstract: Understanding how materials that catalyse the oxygen evolution reaction (OER) function is essential for the development of efficient energy-storage technologies. The traditional understanding of the OER mechanism on metal oxides involves four concerted proton-electron transfer steps on metal-ion centres at their surface and product oxygen molecules derived from water. Here, using in situ 18O isotope labelling mass spectrometry, we provide direct experimental evidence that the O2 generated during the OER on some highly active oxides can come from lattice oxygen. The oxides capable of lattice-oxygen oxidation also exhibit pH-dependent OER activity on the reversible hydrogen electrode scale, indicating non-concerted proton-electron transfers in the OER mechanism. Based on our experimental data and density functional theory calculations, we discuss mechanisms that are fundamentally different from the conventional scheme and show that increasing the covalency of metal-oxygen bonds is critical to trigger lattice-oxygen oxidation and enable non-concerted proton-electron transfers during OER.
1,207 citations
TL;DR: This tutorial review, of relevance for the surface science and heterogeneous catalysis communities, provides a molecular-level discussion of the nature of the active sites in metal catalysis, and establishes a strict partitioning between the so-called "electronic" and "geometrical" effects.
Abstract: This tutorial review, of relevance for the surface science and heterogeneous catalysis communities, provides a molecular-level discussion of the nature of the active sites in metal catalysis. Fundamental concepts such as “Bronsted–Evans–Polanyi relations” and “volcano curves” are introduced, and are used to establish a strict partitioning between the so-called “electronic” and “geometrical” effects. This partitioning is subsequently employed as the basis for defining the concept “degree of structure sensitivity” which can be used when analyzing the structure sensitivity of catalytic reactions.
642 citations
TL;DR: A general principle is concluded that the occupancy of the active cation in the octahedral site is the activity descriptor for the ORR/OER of spinels, consolidating the role of electron orbital filling in metal oxide catalysis.
Abstract: Exploring efficient and low-cost electrocatalysts for the oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER) is critical for developing renewable energy technologies such as fuel cells, metal-air batteries, and water electrolyzers. A rational design of a catalyst can be guided by identifying descriptors that determine its activity. Here, a descriptor study on the ORR/OER of spinel oxides is presented. With a series of MnCo2 O4 , the Mn in octahedral sites is identified as an active site. This finding is then applied to successfully explain the ORR/OER activities of other transition-metal spinels, including Mnx Co3-x O4 (x = 2, 2.5, 3), Lix Mn2 O4 (x = 0.7, 1), XCo2 O4 (X = Co, Ni, Zn), and XFe2 O4 (X = Mn, Co, Ni). A general principle is concluded that the eg occupancy of the active cation in the octahedral site is the activity descriptor for the ORR/OER of spinels, consolidating the role of electron orbital filling in metal oxide catalysis.
487 citations