Concurrently Maximize CO₂RR and Minimize HER: A Dual Catalytic Active Site Approach for Ampere-Level CO₂-to-CO...

The practical application of electrocatalytic CO₂ reduction reaction (CO₂RR) holds a great promise but is hindered by low CO₂ solubility. Under CO₂ mass transfer limitations, the competing hydrogen evolution reaction (HER) is promoted, resulting in a decrease in CO₂RR Faradaic efficiency. Before CO₂ supply reaches its maximum capacity, in neutral or alkaline conditions, increasing CO₂RR selectivity requires additional hydrogen source from solvent H₂O dissociation for CO₂ protonation. However, it is challenging to concurrently achieve CO₂ reduction and H₂O 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-N₃ promotes CO₂ activation and Cr-N₂ accelerates H₂O dissociation. Theoretical investigations unveil the thermodynamic and kinetic superiorities of dual-active-site mechanism. Ni-N₃/Cr-N₂ exhibits higher FE_CO than Ni-N₃, whereas Cr-N₄ 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.