Enhanced CO<sub>2</sub> Electroreduction Selectivity toward Ethylene on Pyrazolate-Stabilized Asymmetric Ni–Cu Hybrid Sites
Liang Huang, Ziao Liu, Ge Gao, Cailing Chen, Yanrong Xue, Jiwu Zhao, Qiong Lei, Mengtian Jin, Chongqin Zhu, Yu Han, Joseph S. Francisco, Lu Xu
Abstract
Metal–organic frameworks (MOFs) possess well-defined, designable structures, holding great potential in enhancing product selectivity for electrochemical CO 2 reduction (CO 2 R) through active site engineering. Here, we report a novel MOF catalyst featuring pyrazolate-stabilized asymmetric Ni/Cu sites, which not only maintains structural stability under harsh electrochemical conditions but also exhibits extraordinarily high ethylene (C 2 H 4 ) selectivity during CO 2 R. At a cathode potential of −1.3 V versus RHE, our MOF catalyst, denoted as Cu 1 Ni-BDP, manifests a C 2 H 4 Faradaic efficiency (FE) of 52.7% with an overall current density of 0.53 A cm –2 in 1.0 M KOH electrolyte, surpassing that on prevailing Cu-based catalysts. More remarkably, the Cu 1 Ni-BDP MOF exhibits a stable performance with only 4.5% reduction in C 2 H 4 FE during 25 h of CO 2 electrolysis. A suite of characterization tools─such as high-resolution transmission electron microscopy, X-ray absorption spectroscopy, operando X-ray diffraction, and infrared spectroscopy─and density functional theory calculations collectively reveal that the cubic pyrazolate–metal coordination structure and the asymmetric Ni–Cu sites in the MOF catalyst synergistically facilitate the stable formation of C 2 H 4 from CO 2 .