Transition-Metal Single Atoms in a Graphene Shell as Active Centers for Highly Efficient Artificial Photosynthesis

Abstract

Utilizing solar energy to fix carbon dioxide (CO2) with water into chemical fuels and oxygen, a mimic process of photosynthesis in nature, is becoming increasingly important but still challenged by the low selectivity and activity, especially in CO2 electrocatalytic reduction. Here we report transition metal atoms coordinated in graphene shell as active centers for aqueous CO2 reduction to carbon monoxide (CO), with high Faradaic efficiencies over 90 % under significant currents up to ~ 60 mA/mg (12 mA/cm2). Three-dimensional atom probe tomography was employed to directly identify the single Ni atomic sites in graphene vacancies. Theoretical simulations suggest that compared to metallic Ni, the Ni atomic sites present significantly different electronic structures which facilitate CO2 to CO conversion and suppress the competing hydrogen evolution reaction dramatically.