Understanding the Mechanism of the Oxygen Evolution Reaction with Consideration of Spin
- PDF / 1,224,076 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 45 Downloads / 178 Views
REVIEW ARTICLE
Understanding the Mechanism of the Oxygen Evolution Reaction with Consideration of Spin Xiaoning Li1 · Zhenxiang Cheng1 · Xiaolin Wang1 Received: 29 June 2020 / Revised: 10 August 2020 / Accepted: 1 October 2020 © Shanghai University and Periodicals Agency of Shanghai University 2020
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. Keywords Oxygen evolution reaction · Water splitting · Spin · Mechanism · Descriptors
1 Introduction The oxygen evolution reaction (OER) is underdeveloped compared with the hydrogen evolution reaction (HER) in overall water splitting. For example, ultrathin twodimensional HER electrocatalysts such as phosphates CoP can achieve cathodic current densities of 20 mA cm−2 at overpotentials of 85 mV due to substantial active sites with low dimensions and good conductivity [1]. Contrastingly, current high-performance OER electrocatalysts such as phosphates Fe-Co-P require high overpotentials of at least 250 mV to achieve anodic current densities of 10 mA cm−2 [2]. And despite nearly a century of research into OER electrocatalysts, its intractably sluggish kinetics * Zhenxiang Cheng [email protected] 1
Institute for Superconducting and Electronic Materials (ISEM), Australia Institute for Innovative Materials, Innovation Campus, University of Wollongong, North Wollongong, NSW 2500, Australia
still inhibits the development of clean energy applications such as rechargeable metal–air batteries, water electrolysis systems and solar fuels devices [3, 4]. O
Data Loading...
