Oxidation State Modulation of Bismuth for Efficient Electrocatalytic Nitrogen Reduction to Ammonia

Electrocatalytic nitrogen reduction reaction (NRR) is a promising strategy for ammonia (NH3) production under ambient conditions. However, it is severely impeded by the challenging activation of the N equivalent to N bond and the competing hydrogen evolution reaction (HER), which makes it crucial to design electrocatalysts rationally for efficient NRR. Herein, the rational design of bismuth (Bi) nanoparticles with different oxidation states embedded in carbon nanosheets (Bi@C) as efficient NRR electrocatalysts is reported. The NRR performance of Bi@C improves with the increase of Bi-0/Bi3+ atomic ratios, indicating that the oxidation state of Bi plays a significant role in electrochemical ammonia synthesis. As a result, the Bi@C nanosheets annealed at 900 degrees C with the optimal oxidation state of Bi demonstrate the best NRR performance with a high NH3 yield rate and remarkable Faradaic efficiency of 15.10 +/- 0.43% at -0.4 V versus RHE. Density functional theory calculations reveal that the effective modulation of the oxidation state of Bi can tune the p-filling of active Bi sites and strengthen adsorption of *NNH, which boost the potential-determining step and facilitate the electrocatalytic NRR under ambient conditions. This work may offer valuable insights into the rational material design by modulating oxidation states for efficient electrocatalysis.

Automated summary

This study reports an efficient NRR electrocatalyst by rational design of Bi nanoparticles and optimization of oxidation state, achieving efficient ammonia synthesis under ambient conditions. By modulating the oxidation state of Bi, the p-filling of active sites and adsorption of *NNH were enhanced, facilitating the electrocatalytic NRR.