n-Bi2MoO6 Nanoflake-Decorated p-CuBi2O4 Microrod Photoanode for Simultaneous Hydrogen Evolution and Rhodamine B Degradation in Alkaline Electrolyte and Natural Seawater

Herein, n-Bi₂MoO₆ nanoflake-decorated p-CuBi₂O₄ microrod photoanode (CB) is successfully fabricated. To the best of the knowledge, this is the first report demonstrating the simultaneous photoelectrocatalysistic (PEC) of RhB degradation and hydrogen evolution using a single photoanode under visible light in both alkaline electrolyte and natural seawater. The enhanced performance of the composite photoanode is attributed to improved charge separation efficiency via the creation of an internal electric field as supported by Mott–Schottky, transient photocurrent, and EIS studies. The proposed PEC mechanism reveals that direct hole oxidation played a decisive role in the degradation of RhB and that the presence of RhB can boost the H₂ production. In natural seawater, the PEC degradation of RhB is markedly improved, attributed to the high conductivity of seawater. Although the hydrogen evolution is significantly suppressed in seawater due mainly to the deposition of Mg(OH)₂ and Ca(OH)₂ at Pt cathode, the findings are the first to show the potential application of p-CuBi₂O₄/n-Bi₂MoO₆ photoanode for PEC water purification and simultaneous renewable energy production in natural seawater. This work may pave the way for more sustainable solutions in water and energy management for real-world applications.