The Role of Cocatalysts on Bismuth Vanadate in the Abatement of Endocrine Disrupting Chemicals and Related Compounds under Visible Light

Visible light photocatalysis is one of the technology pillars contributing to the future energy sustainability based on solar. Here, the the mechanistic roles of cocatalysts deposited on bismuth vanadate (BiVO₄, bandgap 2.45 eV) in the photocatalytic degradation of endocrine disrupting chemicals and related compounds is reported. Because of its low conduction band edge potential, the photocatalytic activity of BiVO₄ is limited by its ability to catalyze an otherwise efficient one-electron reduction of O₂ (to form superoxide radical anion). As such, the deposition of cocatalysts is necessary to promote the alternative multielectron reduction of O₂ in the following order: Pt > Pd > Ag. The general enhancement in activity is traced to the coupled effects of Schottky barrier-type charge separation (a function of the metal cocatalyst work function) and the catalytic surface electron transfer. Although the Pt and Pd deposits are more efficient in the former, the Ag is more active in cocatalyzing the surface charge transfer process. The optimum 2% Pt/BiVO₄ shows high efficiencies in the visible light degradation of bisphenol A, thiodiphenol, and 2,4,6-trichlorophenol; moderate efficiencies toward bisphenol S, 4-chlorophenol and 2,4-dichlorophenol; and ineffective toward diphenyl sulfoxide and triclosan. The trend is related to the adsorption capacity of the substrates on the photocatalyst.