Heterogeneous crystalline–amorphous interface for boosted electrocatalytic nitrogen reduction to ammonia

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) is promising for achieving clean ammonia (NH₃) production under mild conditions but suffers from the difficult adsorption/activation of nitrogen molecules and the severe hydrogen evolution reaction (HER). Herein, crystalline–amorphous interfaces between crystalline Bi and amorphous MoO_x anchored on reduced graphene oxide (RGO) (Bi–MoO_x@RGO) are constructed for achieving the electrochemical NRR. The Bi–MoO_x@RGO electrocatalysts show excellent NRR performance with an NH₃ yield rate of 19.93 ± 0.47 μg h⁻¹ mg⁻¹ at −0.4 V vs. reversible hydrogen electrode (RHE) and a faradaic efficiency of 17.17 ± 0.81% at −0.3 V vs. RHE. The combination of experimental results and theoretical calculations reveals that the boosted NRR performance is due to the crystalline Bi–amorphous MoO_x interfaces which facilitate the adsorption/activation of N₂ while suppressing the competitive HER, thus achieving the simultaneous enhancement of NH₃ yield rate and the faradaic efficiency of the NRR. The utilization of the gas diffusion electrode in the flow cell further increased the NH₃ yield rate to 35.29 ± 1.08 μg h⁻¹ mg⁻¹ at −0.3 V vs. RHE by virtue of enhanced N₂ transportation. This work paves the way for the rational design of electrocatalysts by phase engineering and interface modulation for the efficient electrocatalytic NRR.