Electrocatalytic Oxyanion Reduction: From Fundamental Principles to Rational Catalyst Design
The electrochemical reduction of oxyanions offers a versatile and sustainable pathway for environmental remediation and the synthesis of value-added chemical feedstocks. This review provides a comprehensive analysis of the electrocatalytic conversion of a broad spectrum of oxyanions, including nitrate/nitrite, (bi)carbonate, bromate, perchlorate, (bi)chromate, and selenate/selenite. We highlight the progress in the typical used electrocatalysts and common mechanistic features that govern these reactions, such as multi-electron/proton transfer pathways, key intermediate adsorption, and competitive side processes, and discuss how mechanistic understanding can inform catalyst design. Particular emphasis is placed on the rational design of catalysts to simultaneously enhance activity, selectivity, and stability. We systematically evaluate engineering approaches to boost intrinsic activity, including increasing electrical conductivity and regulating electronic structures, and apparent activity, including exposing highly active facets, reducing the spatial dimensions of active sites, promoting H* generation and tailoring the interfacial microenvironment. To achieve precise product selectivity, we delineate fundamental principles focused on optimizing the adsorption energy for key intermediates, deliberately manipulating atom coupling pathways, and strictly inhibiting the competitive hydrogen evolution reaction. Furthermore, we summarize advanced strategies to address the critical challenge of long-term stability, encompassing both the intrinsic atomic-scale durability of active sites and systemic robustness under practical operational conditions. Finally, we outline emerging opportunities and future directions for developing next-generation electrocatalysts capable of operating at high current densities under practical conditions. This review aims to establish a consolidated mechanistic framework to accelerate the development of advanced catalytic platforms for the sustainable conversion of oxyanion pollutants and feedstocks.