Design and performance of a promising Z-scheme photocatalyst: a BP/PtO2 heterojunction for efficient water splitting

Photocatalytic water splitting harnesses solar energy to produce clean hydrogen, addressing energy and environmental challenges. Z-scheme heterojunctions improve charge separation and light utilization while maintaining high redox power, boosting photocatalytic efficiency. Taking first-principles theory as the foundation, this paper comprehensively examines the geometrical structure, electronic features, and light-driven catalytic behavior of the BP/PtO₂ heterojunction. The BP/PtO₂ heterostructure exhibits a typical Type-II band alignment and Z-scheme carrier transport mechanism. The indirectly narrow bandgap of 1.309 eV and special transport modes promote the segregation of photogenerated carriers. Moreover, the band edge alignment of the BP/PtO₂ heterojunction covers the potential range necessary for water splitting at pH values less than or equal to 7, allowing the material to facilitate photocatalytic reactions in acidic environments. During water decomposition, the reduction reaction is dominated by the conduction band (CB) of BP to produce hydrogen, while the oxidation reaction occurs on the valence band (VB) of PtO₂ to produce oxygen; these reactions promote water decomposition. Under compressive strain ranging from 0 to 5%, the energy band structure of the heterojunction remains suitable for driving water splitting reactions under acidic conditions. Finally, the BP/PtO₂ heterojunction exhibits excellent light absorption performance, with a light absorption peak of 2.67 × 10⁵ cm⁻¹. Both tensile and compressive strains enhance the heterojunction's ability to absorb light, thereby improving its optical performance. The BP/PtO₂ heterojunction is a promising candidate for photocatalytic water decomposition.