Ligand-Controlled Electroreduction of CO₂ to Formate over Facet-Defined Bimetallic Sulfide Nanoplates

CO₂ reduction (CO₂R) catalyzed by an efficient, stable, and earth-abundant electrocatalyst offers an attractive means to store energy derived from renewable sources. Here, we describe the synthesis of facet-defined Cu₂SnS₃ nanoplates and the ligand-controlled CO₂R property. We show that thiocyanate-capped Cu₂SnS₃ nanoplates possess excellent selectivity toward formate over a wide range of potentials and current densities, attaining a maximum formate Faradaic efficiency of 92% and partial current densities as high as 181 mA cm^-2 when tested using a flow cell with gas-diffusion electrode. In situ spectroscopic measurements and theoretical calculations reveal that the high formate selectivity originates from favorable adsorption of HCOO* intermediates on cationic Sn sites that are electronically modulated by thiocyanates bound to adjacent Cu sites. Our work illustrates that well-defined multimetallic sulfide nanocrystals with tailored surface chemistries could provide a new avenue for future CO₂R electrocatalyst design.