Exfoliated Ultrathin ZnIn₂S₄ Nanosheets with Abundant Zinc Vacancies for Enhanced CO₂ Electroreduction to Formate

Electrocatalytic conversion of carbon dioxide (CO₂) is promising for balancing carbon cycles while producing value-added feedstocks. Herein, ultrathin ZnIn₂S₄ nanosheets with abundant Zn vacancies are demonstrated for electrochemically reducing CO₂ to formate. Specifically, a partial current density of 245 mA cm⁻² with a near-unity faradaic efficiency of 94 % for formate generation was achieved over the ultrathin ZnIn₂S₄ nanosheets in a flow cell configuration. Experimental and theoretical results revealed that abundant Zn vacancies in the ultrathin ZnIn₂S₄ nanosheets with a high electrochemically active surface area synergistically optimized the intermediate binding energy and contributed to the boosted selectivity and activity. This work may provide useful understandings in designing efficient catalysts for selective CO₂ electroreduction.