Increasing exposure of atomically dispersed Ni sites via constructing hierarchically porous supports for enhanced electrochemical CO2 reduction

Abstract

Abstract Atomically dispersed metal catalysts have been widely utilized for electrocatalysis, such as the electrochemical reduction of CO2, due to their low coordination number and maximum utilization of metal active sites. However, it remains a major challenge to develop an effective and convenient strategy for fully exposing the active sites of atomically dispersed metal catalysts within supports. Herein, we describe an operationally simple and sustainable strategy for preparing hierarchically porous thin-wall carbon networks with highly exposed atomically dispersed Ni sites by directly pyrolyzing a ground mixture of metal salts and organic ligands. Compared with the preformed metal organic framework-derived materials, the amount of exposed active Ni sites can be increased by ~50% for hierarchically porous materials. The hierarchically porous atomically dispersed Ni electrocatalyst shows obviously enhanced CO2RR catalytic performance with higher CO Faradaic efficiency (over 99% at −0.88\xa0V) and high TOF value of 7025\xa0h−1 (72.6% higher than that for the metal organic framework-derived materials). The excellent activity can be attributed to the increased exposure of atomically dispersed Ni sites with hierarchically porous structure and interconnected thin-wall carbon networks, which ensure the fully exposure of electrocatalytically active sites and promotion of mass transport and electron transfer. Density functional theory calculations further suggest that the fully exposed Ni sites are responsible for highly efficient activation of CO2 rather than the carbon layer-covered Ni sites.