ABSTRACT The low stability of copper‐based catalysts caused by dynamic reconstruction during the electrocatalytic CO 2 reduction (ECR) process restricts their practical applications. Here, we developed a high performance Cu 2 O polycrystalline catalyst for the ECR, featuring enhanced stability and selectivity toward multi‐carbon products. This is achieved through targeted grain boundary engineering (GBE) where the grain size and boundary density of the catalyst were manipulated via varying the concentrations of metal source and precipitant. The as‐prepared catalyst with an optimal grain size and high boundary density demonstrated an excellent selectivity (> 80%) toward multi‐carbon products under ampere‐level current density and a promising stability (∼100 h) under industry‐related conditions (200 mA cm −2 ). By employing in situ and online characterization techniques, it was found that Cu 2 O catalyst with moderate grain sizes exhibited the lowest dissolution and reconstruction rates during ECR resulting in significantly enhanced stability. Furthermore, a volcano‐like relationship between the grain size and ECR stability was identified. The beneficial impacts of concave grain boundaries on the stability of Cu‐based catalysts were evidenced, and insights into the molecular interactions at play as well as the origin of the observed volcano‐like relationship were obtained by density functional theory (DFT) calculations.
Zhang et al. (2025) studied this question.