Photoelectrocatalytic Degradation of Rhodamine B in the Presence of TiO₂-BiVO₄

The discharge of printing and dyeing wastewater has become a key concern in global water pollution control due to its high pollutant concentration, dark color, refractory biodegradability and toxic characteristics. Photoelectrocatalytic (PEC) technology has gained widespread attention as it can effectively treat refractory organic pollutants. In this study, titanium dioxide (TiO₂)-bismuth vanadate (BiVO₄) composite materials were synthesized through the sol-gel/solvothermal hybrid method, and layered heterojunction structures were fabricated via sol-gel precursor preparation followed by spin-coating deposition. The PEC degradation efficiency of rhodamine B (RhB) was systematically evaluated under varying operational conditions in the presence of TiO₂-BiVO₄. The four-layer BiVO₄/four-layer TiO₂ material showed the optimal catalytic activity among the tested structures, achieving an 80.3% removal of RhB under an applied bias of 4 V and illumination intensity of 14,000 lx. Through the equilibrium adjustment of the Fermi levels, the type Ⅱ heterostructure was formed. Moreover, superoxide radical (O₂^-) was identified as the predominant reactive oxygen species driving the degradation mechanism. Mechanistic analysis revealed that RhB degradation was accomplished through deethylation, benzene ring cleavage, and subsequent ring-opening mineralization. This study prepared an efficient PEC material, which provides a theoretical basis for the PEC treatment of printing and dyeing wastewater.