Meng Zhou, Yiyong Wang, Shiqiang Liu, Yaoyu Yin, Yaguang Peng, Jiapeng Jiao, Jiahao Yang, Wengling Zhao, Hengan Wang, Ran Duan, Qinggong Zhu, Xiaofu Sun, Yi Xu, Jianling Zhang, Xinchen Kang, Buxing Han
Abstract Electrochemical CO 2 methanation is crucial for sustainable carbon recycling, transforming a greenhouse gas into a valuable fuel. However, achieving high selectivity toward CH 4 , particularly at high current densities, remains a significant challenge. In this study, a remarkable Faradaic efficiency for CH 4 (FE CH4 ) of 88.7% with a current density of 461.0 mA cm −2 was achieved at −1.3 V vs. RHE over CuCeSiO x electrode in a ternary electrolyte of 1 M tetrapropylammonium hydroxide (TPAOH) + 5 mM KCl, setting a new record for CO 2 electroreduction to CH 4 . By employing other Cu‐based catalysts, high CH 4 selectivity can also be obtained in this ternary electrolyte. Mechanistic studies reveal the synergistic effect of mixed K + and TPA + in the electrochemical double layer plays a critical role in controlling the reaction pathway. Specifically, K + modulates *CO adsorption and promotes water dissociation, generating abundant H • radicals, while TPA + aggregates stabilize these radicals, accelerating the reaction kinetics, and facilitating the deep hydrogenation from *CO to CH 4 .