Electronically Coupled SnO2 Quantum Dots and Graphene for Efficient Nitrogen Reduction Reaction

Abstract

Electrocatalytic N 2 reduction reaction (NRR) provides an effective and renewable approach for artificial NH 3 production, but still remains a grand challenge because of the low NH 3 yield and Faradaic efficiency (FE). Herein, we reported that the SnO 2 quantum dots (QDs) supported on reduced graphene oxide (RGO) could efficiently and stably catalyze NRR at ambient conditions. The NRR performance of resulting SnO 2 /RGO was studied by both experimental techniques and density functional theory calculations. It was found that the ultrasmall SnO 2 QDs (2 nm) grown on RGO could provide abundant sites for efficient N 2 adsorption. Significantly, the strongly electronically coupled SnO 2 QDs and RGO brought about the enhanced conductivity and the decreased work function, which led to a considerably lowered energy barrier of *N 2 → *N 2 H that was the rate-determining step of the NRR process. Meanwhile, the SnO 2 /RGO exhibited inferior hydrogen evolution reaction activity. As a result, the SnO 2 /RGO delivered a high NH 3 yield of 25.6 μg h –1 mg –1 (5.1 μg cm –2 h –1 ) and an FE of 7.1% in 0.1 M Na 2 SO 4 at −0.5 V (vs RHE), together with the outstanding selectivity and stability, endowing it as a promising electrocatalyst for N 2 fixation.