Concurrently Maximize CO ₂ RR and Minimize HER: A Dual Catalytic Active Site Approach for Ampere‐Level CO ₂ ‐to‐CO Electrolysis

Abstract

Abstract The practical application of electrocatalytic CO 2 reduction reaction (CO 2 RR) holds a great promise but is hindered by low CO 2 solubility. Under CO 2 mass transfer limitations, the competing hydrogen evolution reaction (HER) is promoted, resulting in a decrease in CO 2 RR Faradaic efficiency. Before CO 2 supply reaches its maximum capacity, in neutral or alkaline conditions, increasing CO 2 RR selectivity requires additional hydrogen source from solvent H 2 O dissociation for CO 2 protonation. However, it is challenging to concurrently achieve CO 2 reduction and H 2 O dissociation at single active site. Herein, we synthesized a neighboring Ni‐Cr atomic pair configuration with distance of ∼2.7 Å. COMSOL Multiphysics finite‐element studies demonstrate that appropriate distance between dual active sites should be on the order of a few angstroms. Operando XAS and soft NEXAFS characterizations indicate that the Ni‐N 3 promotes CO 2 activation and Cr‐N 2 accelerates H 2 O dissociation. Theoretical investigations unveil the thermodynamic and kinetic superiorities of dual‐active‐site mechanism. Ni‐N 3 /Cr‐N 2 exhibits higher FE CO than Ni‐N 3 , whereas Cr‐N 4 displays a strong preference for HER. The zero‐gap MEA attains J of up to −1000 mA cm −2 with a FE CO exceeding 85% at a cell voltage of −4.0 V, and maintains stable operation for over 100 h at a J of −200 mA cm −2 .