Graphene Quantum Sheet Catalyzed Silicon Photocathode for Selective CO₂ Conversion to CO

Abstract

The reduction of carbon dioxide (CO 2 ) into chemical feedstock is drawing increasing attention as a prominent method of recycling atmospheric CO 2 . Although many studies have been devoted in designing an efficient catalyst for CO 2 conversion with noble metals, low selectivity and high energy input still remain major hurdles. One possible solution is to use the combination of an earth‐abundant electrocatalyst with a photoelectrode powered by solar energy. Herein, for the first time, a p‐type silicon nanowire with nitrogen‐doped graphene quantum sheets (N‐GQSs) as heterogeneous electrocatalyst for selective CO production is demonstrated. The photoreduction of CO 2 into CO is achieved at a potential of −1.53 V versus Ag/Ag + , providing 0.15 mA cm −2 of current density, which is 130 mV higher than that of a p‐type Si nanowire decorated with well‐known Cu catalyst. The faradaic efficiency for CO is 95%, demonstrating significantly improved selectivity compared with that of bare planar Si. The density functional theory (DFT) calculations are performed, which suggest that pyridinic N acts as the active site and band alignment can be achieved for N‐GQSs larger than 3 nm. The demonstrated high efficiency of the catalytic system provides new insights for the development of nonprecious, environmentally benign CO 2 utilization.