Understanding the key role of vanadium in p-type BiVO4 for photoelectrochemical N2 fixation

The photoelectrochemical N 2 reduction reaction (PEC NRR) is extremely charming to the synthetic ammonia (NH 3 ), for its mild operating conditions and low carbon footprint. Taking account of the strong chemical inertness of N 2 and competitive hydrogen evolution reaction, it is necessary to explore a robust and stable photoelectrocatalyst. Herein, a robust p-type BiVO 4 (p-BiVO 4 ) photocathode is firstly reported for NRR under ambient conditions. Interestingly, V sites are proved as the mainly ideal active center for N 2 adsorption/activation based on the density functional theory (DFT) calculations. The ammonia evolution rate ( V NH3 : 11.6 × 10 −8  mol h −1  cm −2 ) and Faradaic efficiency (16.2%) were obtained at −0.1 V vs. RHE in 0.1 M Li 2 SO 4 solution, outperforming most of the photoelectrocatalysts reported thus far. Moreover, the 1 H nuclear magnetic resonance result confirmed that the source of N was completely from the feeding N 2 gas. This work provided a new opportunity to tap the V-based photocathode in the field of PEC NRR.