Electrochemistry-Assisted Photoelectrochemical Reduction of Nitrogen to Ammonia

Ammonia (NH₃) is a basic chemical feedstock for the production of fertilizers and pharmaceuticals, and it emerges as a new hydrogen energy carrier for renewable energy sources such as solar and wind power. A photoelectrochemical nitrogen reduction reaction (PEC NRR) under mild operating conditions represents a potentially green and convenient approach for the synthesis of NH₃. However, a generally applicable PEC NRR featuring a high NH₃ yield and a satisfactory conversion efficiency remains elusive. Herein, we report on a simple and effective electrochemistry-assisted strategy to enhance the PEC fixation of N₂ to NH₃. Using this strategy, we harness a steel-based cathode-assisted Au/SiO₂/Si photocathode to seamlessly combine two critical reaction stepsN₂ activation and hydrogenationto realize an NH₃ yield rate of 22.0 μg·cm^–2·h^–1 and a faradic efficiency of 23.7% at −0.2 V versus a reversible hydrogen electrode under one sun illumination. We also provide an accessible reaction setup to avoid the disturbance of a contamination by air, human breath, and N₂ stream, leading to a reliable production of NH₃ by the PEC NRR. An operando characterization and a theoretical calculation uncover the active sites and reaction mechanism of the whole system for an electrochemistry-assisted PEC NRR. This work demonstrates the capability of an electrochemistry-assisted excitation in PEC NRR, and it introduces a new design concept for addressing pertinent challenges in photoelectrochemical and other chemical fields.