The p-Orbital Delocalization of Main-Group Metals to Boost CO2 Electroreduction

Abstract

Enhancing the p-orbital delocalization of a Bi catalyst (termed as POD-Bi) via layer coupling of the short inter-layer Bi-Bi bond facilitates the adsorption of intermediate *OCHO of CO₂ and thus boosts the CO₂ reduction reaction (CO₂ RR) rate to formate. X-ray absorption fine spectroscopy shows that the POD-Bi catalyst has a shortened inter-layer bond after the catalysts are electrochemically reduced in situ from original BiOCl nanosheets. The catalyst on a glassy carbon electrode exhibits a record current density of 57 mA cm^-2 (twice the state-of-the-art catalyst) at -1.16 V vs. RHE with an excellent formate Faradic efficiency (FE) of 95 %. The catalyst has a record half-cell formate power conversion efficiency of 79 % at a current density of 100 mA cm^-2 with 93 % formate FE when applied in a flow-cell system. The highest rate of the CO₂ RR production reported (391 mg h^-1 cm² ) was achieved at a current density of 500 mA cm^-2 with formate FE of 91 % at high CO₂ pressure.

Keywords: CO2 electroreduction; bismuth; delocalization; formate; heterogeneous catalysis.