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

Electrocatalytic N₂ reduction reaction (NRR) provides an effective and renewable approach for artificial NH₃ production, but still remains a grand challenge because of the low NH₃ yield and Faradaic efficiency (FE). Herein, we reported that the SnO₂ quantum dots (QDs) supported on reduced graphene oxide (RGO) could efficiently and stably catalyze NRR at ambient conditions. The NRR performance of resulting SnO₂/RGO was studied by both experimental techniques and density functional theory calculations. It was found that the ultrasmall SnO₂ QDs (2 nm) grown on RGO could provide abundant sites for efficient N₂ adsorption. Significantly, the strongly electronically coupled SnO₂ QDs and RGO brought about the enhanced conductivity and the decreased work function, which led to a considerably lowered energy barrier of *N₂ → *N₂H that was the rate-determining step of the NRR process. Meanwhile, the SnO₂/RGO exhibited inferior hydrogen evolution reaction activity. As a result, the SnO₂/RGO delivered a high NH₃ yield of 25.6 μg h^–1 mg^–1 (5.1 μg cm^–2h^–1) and an FE of 7.1% in 0.1 M Na₂SO₄ at −0.5 V (vs RHE), together with the outstanding selectivity and stability, endowing it as a promising electrocatalyst for N₂ fixation.