Enhancing Rhodamine B Adsorption on Bi₄Ti₃O₁₂ Nanoplates Prior to Catalysis via the Synergistic Effect of Light and Ultrasound

Bismuth titanate (Bi₄Ti₃O₁₂, BiTO) has gained significant interest in piezo-photocatalysis. Adsorption, as a key prerequisite for catalytic reactions, directly affects factors such as the activation degree of reactants and reaction pathways, playing a significant role in regulating subsequent catalytic processes. However, there is still a lack of relevant research on the adsorption process of BiTO. In this work, highly crystalline BiTO nanosheets synthesized via a molten-salt method are used to systematically investigate the impacts of light, ultrasound, and pH of the solution on the adsorption performance toward photocatalytic degradation of dyes. The results demonstrate that BiTO exhibits enhanced RhB adsorption under acidic conditions. Notably, under the synergistic effect of light and ultrasound, the adsorption rate increased to 34.15 × 10⁻³ min⁻¹, which is eight times higher than that without external stimuli. Mechanism analysis reveals that the piezoelectric effect induces surface polarization charges and forms a built-in electric field, which promotes the separation of photogenerated carriers and significantly alters the surface potential of the catalyst, thereby enhancing the electrostatic attraction toward RhB molecules. This study highlights the crucial role of external stimuli in regulating the adsorption in piezo-photocatalytic systems, provides new insights into understanding and optimizing the interfacial mechanisms in dye degradation, and offers alternative perspectives for improving the efficiency of piezo-photocatalytic materials in water pollution treatment.