Catalytic engineering of a cerium vanadate–bismuth vanadate system to yield a bifunctional photocatalyst for simultaneous hydrogen generation and pollutant degradation

Abstract

A cerium vanadate–bismuth vanadate (CV–BV) composite is developed to facilitate dual functionality in photocatalytic hydrogen generation and degradation and is synthesized via a one pot hydrothermal method. Despite its strong pollutant degradation capability, BV remains ineffective for hydrogen evolution, whereas CV, with favourable band position, actively participates in hydrogen evolution. BV shows a pollutant degradation rate of 90% in 1 hour but does not produce hydrogen, while CV exhibits a hydrogen evolution rate of 590.0 μmol h⁻¹ g⁻¹ but only a 10% degradation of methyl orange (MO) for the same duration. Notably, the CV–BV heterojunction, governed by an S-scheme mechanism that favours charge carrier separation and redox potential, exhibits excellent performance, simultaneously achieving a hydrogen evolution rate of 1011 μmol h⁻¹ g⁻¹ and a 98% degradation efficiency for MO. The total organic carbon analysis indicates 93% removal of organic carbon from the dye solution. The system maintains stable catalytic performance over five consecutive cycles, indicating its durability. The solar-to-hydrogen (STH) efficiency for the CV–BV system is determined to be 3.99%. The activity of the CV–BV catalyst is demonstrated in actual wastewater, achieving 96% dye degradation and 803.0 μmol h⁻¹ g⁻¹ hydrogen generation. Its dual performance remained effective even in MO-contaminated seawater (310.0 μmol h⁻¹ g⁻¹ and 98% MO degradation), proving its adaptability to harsh, complex environments. The heterojunction efficiently absorbs a broad light spectrum, generating electron–hole pairs, and conduction band electrons of CV participate in proton reduction to produce hydrogen in the presence of a hole scavenger while superoxide radicals partake in degradation as proven from the radical trapping experiments. The synergistic S-scheme charge transfer mechanism within the CV–BV system enhances its bifunctional efficiency, demonstrating significant potential for fuel generation from wastewater with simultaneous environmental remediation.