Half reaction over a Ni2P/Bi2O2S composite for photocatalytic overall nitrogen fixation

Abstract

Nitrate and ammonium are recognized as essential industrial feedstocks; however, the conventional synthesis procedure causes high energy consumption and massive greenhouse gas emission. Photocatalysis offers an environmentally friendly alternative for green nitrogen fixation to produce nitrates and ammonium compounds. However, the effectiveness is still limited by the low utilization of visible light and the rapid recombination of photogenerated charge carriers. This work detailed the synthesis and characterization of a Bi₂O₂S/Ni₂P composite material with a distinctive S-scheme heterojunction, which unveiled superior photocatalytic overall nitrogen fixation activity. The optimized sample, denoted as the Bi₂O₂S–Ni₂P 0.1 composite, demonstrated a nitrate yield of 103.9 μmol g⁻¹ h⁻¹ and an ammonium yield of 353.3 μmol g⁻¹ h⁻¹. The experimental findings, supported by a comprehensive analytical characterization, revealed the formation of a unique S-scheme charge transfer pathway at the Bi₂O₂S/Ni₂P interface. This pathway could effectively separate photogenerated electron–hole pairs and optimize their redox potential, leading to the observed high photocatalytic efficiency. This study provides novel insights into the design of Bi₂O₂S-based photocatalysts for efficient overall nitrogen fixation driven by the S-scheme charge transfer mechanism.