Electron-Rich Bismuth Enabled π-Backdonation in Ni–Bi2MoO6 for Efficient Ammonia Synthesis

Abstract

The inherent high activation energy barrier of the N₂ molecule severely impedes the practical application of electrocatalytic nitrogen reduction reaction (NRR). To overcome this bottleneck, this study employs a Ni²⁺ doping strategy to precisely modulate the electronic structure of bismuth molybdate, inducing the formation of electron-rich sites on adjacent Bi³⁺ ions and transforming them into efficient π-backdonation donor centers. This significantly accelerates electron transfer into the N₂ antibonding orbitals, promoting N₂ activation. Consequently, under 0.1 M HCl electrolyte and an applied potential of −0.2 V versus RHE, the catalyst achieves an exceptional ammonia yield of 92.3 µg mg⁻¹ h⁻¹ and a Faradaic efficiency of 72.6%, surpassing the performance of most reported NRR catalysts. In situ diffuse reflectance Fourier transform infrared spectroscopy confirms the π-backdonation mechanism is crucial for efficient N≡N bond activation, while cycling tests highlight the material's outstanding stability. This work lays the groundwork for developing highly efficient and selective NRR catalysts and significantly advances sustainable ammonia synthesis technologies.