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掺杂氧化镍上水氧化机理的光谱电化学分析

Spectroelectrochemical Analysis of the Water Oxidation Mechanism on Doped Nickel Oxides.

作者信息

Rao Reshma R, Corby Sacha, Bucci Alberto, García-Tecedor Miguel, Mesa Camilo A, Rossmeisl Jan, Giménez Sixto, Lloret-Fillol Julio, Stephens Ifan E L, Durrant James R

机构信息

Department of Chemistry, Centre for Processable Electronics, Imperial College London, London W12 0BZ, U.K.

Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avinguda Països Catalans 16, 43007 Tarragona, Spain.

出版信息

J Am Chem Soc. 2022 May 4;144(17):7622-7633. doi: 10.1021/jacs.1c08152. Epub 2022 Apr 20.

Abstract

Metal oxides and oxyhydroxides exhibit state-of-the-art activity for the oxygen evolution reaction (OER); however, their reaction mechanism, particularly the relationship between charging of the oxide and OER kinetics, remains elusive. Here, we investigate a series of Mn-, Co-, Fe-, and Zn-doped nickel oxides using UV-vis spectroscopy coupled with time-resolved stepped potential spectroelectrochemistry. The Ni/Ni redox peak potential is found to shift anodically from Mn- < Co- < Fe- < Zn-doped samples, suggesting a decrease in oxygen binding energetics from Mn- to Zn-doped samples. At OER-relevant potentials, using optical absorption spectroscopy, we quantitatively detect the subsequent oxidation of these redox centers. The OER kinetics was found to have a second-order dependence on the density of these oxidized species, suggesting a chemical rate-determining step involving coupling of two oxo species. The intrinsic turnover frequency per oxidized species exhibits a volcano trend with the binding energy of oxygen on the Ni site, having a maximum activity of ∼0.05 s at 300 mV overpotential for the Fe-doped sample. Consequently, we propose that for Ni centers that bind oxygen too strongly (Mn- and Co-doped oxides), OER kinetics is limited by O-O coupling and oxygen desorption, while for Ni centers that bind oxygen too weakly (Zn-doped oxides), OER kinetics is limited by the formation of oxo groups. This study not only experimentally demonstrates the relation between electroadsorption free energy and intrinsic kinetics for OER on this class of materials but also highlights the critical role of oxidized species in facilitating OER kinetics.

摘要

金属氧化物和羟基氧化物在析氧反应(OER)中展现出了先进的活性;然而,它们的反应机理,尤其是氧化物的电荷与OER动力学之间的关系,仍然难以捉摸。在此,我们使用紫外可见光谱结合时间分辨阶梯电位光谱电化学法研究了一系列锰、钴、铁和锌掺杂的氧化镍。发现镍/镍氧化还原峰电位从锰掺杂 < 钴掺杂 < 铁掺杂 < 锌掺杂的样品中阳极移动,这表明从锰掺杂到锌掺杂的样品中氧结合能降低。在与OER相关的电位下,使用光吸收光谱,我们定量检测了这些氧化还原中心的后续氧化。发现OER动力学对这些氧化物种的密度具有二级依赖性,这表明涉及两个氧代物种耦合的化学速率决定步骤。每个氧化物种的本征周转频率随镍位点上氧的结合能呈现火山趋势,对于铁掺杂样品,在300 mV过电位下具有约0.05 s的最大活性。因此,我们提出,对于那些与氧结合过强的镍中心(锰和钴掺杂的氧化物),OER动力学受O - O耦合和氧脱附限制,而对于那些与氧结合过弱的镍中心(锌掺杂的氧化物),OER动力学受氧代基团形成限制。这项研究不仅通过实验证明了这类材料上OER的电吸附自由能与本征动力学之间的关系,还突出了氧化物种在促进OER动力学中的关键作用。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/3900/9073940/217862ea8e17/ja1c08152_0002.jpg

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