Dual-Site Activation for Efficient Acidic CO₂ Electroreduction at Industrial-Level Current Densities.

Abstract

Electroreduction of CO₂ to formic acid in acidic media offers a promising approach for value-added CO₂ utilization. However, achieving high selectivity for formic acid in acidic electrolytes remains challenging due to the competitive hydrogen evolution reaction (HER), particularly at industrially relevant current densities. Herein, a charge redistribution modulation strategy is demonstrated by constructing the CuS /SnS₂ Mott-Schottky catalyst to enhance formic acid selectivity. Experiments and calculation results reveal the broadening of Sn orbitals and reduced orbital symmetry of Sn orbitals contribute to enhanced CO₂ adsorption, while the modulated Cu sites with a stronger Lewis acid character stabilize ^*OCHO intermediates more effectively. This enables dual-site activation for efficient CO₂ electroreduction into formic acid synthesis. Consequently, the optimized CuS/SnS₂ catalysts achieve a maximum formic acid Faradaic efficiency (FE) of 99% in acidic electrolytes and maintain selectivity above 80% at a current density of 1 A cm^-2, significantly surpassing the performance of CuS and SnS₂ alone. Moreover, the excellent selectivity across pH-universal electrolytes demonstrates that dual-site activation is a promising strategy for designing highly efficient CO₂ reduction reaction catalysts.