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ArticleCathodic Corrosion-Induced Structural Evolution of CuNi Electrocatalysts for Enhanced CO2 ReductionWenjin Sun 1,†, Bokki Min 2,†, Maoyu Wang 3, Xue Han 4, Qiang Gao 1, Sooyeon Hwang 5, Hua Zhou 3, and Huiyuan Zhu 1,2,*1 Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA2 Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904, USA3 Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA4 Department of Chemical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA5 Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA* Correspondence: kkx8js@virginia.com† These authors contributed equally to this work.Received: 22 October 2024; Revised: 25 November 2024; Accepted: 27 November 2024; Published: 4 December 2024 Abstract: The electrochemical CO2 reduction reaction (CO2RR) has attracted significant attention as a promising strategy for storing intermittent energy in chemical bonds while sustainably producing value-added chemicals and fuels. Copper-based bimetallic catalysts are particularly appealing for CO2RR due to their unique ability to generate multi-carbon products. While substantial effort has been devoted to developing new catalysts, the evolution of bimetallic systems under operational conditions remains underexplored. In this work, we synthesized a series of CuxNi1−x nanoparticles and investigated their structural evolution during CO2RR. Due to the higher oxophilicity of Ni compared to Cu, the particles tend to become Ni-enriched at the surface upon air exposure, promoting the competing hydrogen evolution reaction (HER). At negative activation potentials, cathodic corrosion has been observed in CuxNi1−x nanoparticles, leading to the significant Ni loss and the formation of irregularly shaped Cu nanoparticles with increased defects. This structural evolution, driven by cathodic corrosion, shifts the electrolysis from HER toward CO2 reduction, significantly enhancing the Faradaic efficiency of multi-carbon products (C2+).