Exploiting MoSi2N4, WSi2N4 and WGe2N4 monolayers for efficient photocatalytic overall water splitting across a broad pH range†

The pursuit of developing highly potent and environmentally friendly photocatalysts for water dissociation is crucial for the advancement and storage of unlimited solar energy, although it remains a massive challenge. Herein, we conducted a screening process for the photocatalytic water splitting capabilities of a multitude of members from the extensive MA₂N₄ family. Using first-principles calculations, we found MoSi₂N₄, WSi₂N₄ and WGe₂N₄ structures with excellent potential for photocatalytic applications. To be specific, these members possess semiconductor characteristics, featuring suitable band gap structures and pronounced optical absorption capabilities in the UV-visible light spectrum. Our findings suggest that with nitrogen vacancies present on the surface, MoSi₂N₄, WSi₂N₄, and WGe₂N₄ all demonstrate near-zero Gibbs free energy in driving the hydrogen evolution reaction. Simultaneously, MoSi₂N₄, WSi₂N₄, and WGe₂N₄ can spontaneously catalyze the overall water splitting reaction under light illumination at pH values of 4, 12, and 8, respectively. This investigation provides fresh perspectives in terms of designing highly efficient photocatalysts.