Phase-evolved BiOCl/Bi3O4Cl S-scheme Heterojunction for Enhanced Photocatalytic Nitrogen Fixation

Abstract

Photocatalytic nitrogen reduction provides a sustainable alternative to conventional ammonia synthesis but is limited by inefficient charge separation and sluggish N2 activation. In this work, molecular dynamics simulations were first performed to evaluate the thermodynamic feasibility of the BiOCl to Bi3O4Cl phase evolution, providing theoretical guidance for interface construction. Guided by these insights, a BiOCl/Bi3O4Cl heterojunction nanosheet was subsequently fabricated via an in situ solvothermal strategy. Structural and spectroscopic analyses confirm the intimate interfacial contact and the formation of a built-in electric field. Optical, electrochemical, and theoretical results reveal that the heterojunction exhibits enhanced light absorption and efficient directional charge transfer. Density functional theory calculations further demonstrate that interfacial electronic redistribution lowers the reaction barrier for nitrogen activation. In-situ DRIFTS analysis indicates that nitrogen reduction proceeds preferentially through a distal associative pathway. Results show that, without sacrificial agents, the nitrogen fixation rate of BiOCl/Bi3O4Cl reaches 93.7 μmol g-1 h-1. As a result, the BiOCl/Bi3O4Cl heterojunction delivers significantly improved photocatalytic ammonia production under mild conditions. This study demonstrates a theory-guided route for constructing efficient heterojunction photocatalysts for sustainable nitrogen fixation.