Structure-performance driven discovery of efficient Bi2S3 monolayer photocatalysts for solar water splitting

Developing efficient and stable photocatalysts is critical for solar-driven hydrogen production. However, the structural diversity of metal sulfide systems poses challenges for rational material design. Here, we perform high-throughput first-principles screening of 1038 Bi₂S₃ monolayer allotropes to identify promising candidates for overall water splitting. Sixteen structures are dynamically stable, and seven exhibit appropriate band edge positions and overpotentials. Notably, six candidates achieve solar-to-hydrogen efficiencies exceeding 10 %, with Bi₂S₃-IV reaching 20.77 %. Ab initio molecular dynamics simulations confirm their thermodynamic stability, while Gibbs free energy analyses reveal favorable hydrogen and oxygen evolution reaction pathways. A feasible structural transformation from Bi₂S₃-I to Bi₂S₃-IV is identified via nudged elastic band calculations. Additionally, nanosecond-scale carrier lifetimes and low exciton binding energies suggest excellent charge separation and transport. The outstanding performance originates from unique structural motifs that induce internal electric fields and enhance light absorption. This work provides a robust structure-guided design framework for discovering efficient two-dimensional photocatalysts for solar fuel generation.