Synergy of Bi2O3 and RuO2 Nanocatalysts for Low-Overpotential and Wide pH-Window Electrochemical Ammonia Synthesis

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is still seriously impeded by the inferior NH3 yield and low Faradaic efficiency, especially at low overpotentials. Herein, we report the synthesis of nano-sized RuO2 and Bi2O3 particles grown on functionalized exfoliated graphene (FEG) through in situ electrodeposition, denoted as RuO2-Bi2O3/FEG. The prepared self-supporting RuO2-Bi2O3/FEG hybrid with a Bi mass loading of 0.70 wt% and Ru mass loading of 0.04 wt% shows excellent NRR performance at low overpotentials in acidic, neutral and alkaline electrolytes. It achieves a large NH3 yield of 4.58 +/- 0.16 mu g(NH3) h(-1) cm(-2) with a high Faradaic efficiency of 14.6 % at -0.2 V versus reversible hydrogen electrode in 0.1 M Na2SO4 electrolyte. This performance benefits from the synergistic effect between Bi2O3 and RuO2 which respectively have a fairly strong interaction of Bi 6p orbitals with the N 2p band and abundant supply of *H, as well as the binder-free characteristic and the convenient electron transfer via graphene nanosheets. This work highlights a new electrocatalyst design strategy that combines transition and main-group metal elements, which may provide some inspirations for designing low-cost and high-performance NRR electrocatalysts in the future.

Automated summary

In this study, nano-sized RuO2-Bi2O3 particles were synthesized on FEG, showing excellent NRR performance in acidic, neutral, and alkaline electrolytes with high NH3 yield and Faradaic efficiency achieved at low overpotentials. The synergistic effect between Bi2O3 and RuO2, as well as the binder-free characteristic and convenient electron transfer via graphene nanosheets, contribute to the superior NRR performance. This work highlights a new electrocatalyst design strategy that may inspire future development of low-cost and high-performance NRR electrocatalysts.