Modulating the oxidative active species by regulating the valence of palladium cocatalyst in photocatalytic degradation of ciprofloxacin

Nano-structured metal cocatalysts are easy to be oxidized and form mixed valences and interfaces which would facilitate the catalytic performance in previous studies. Herein, as an example in photocatalysis, three kinds of Pd cocatalysts with various valence distributions (PdO70-Pd30/CN, PdO50-Pd50/CN and PdO30-Pd70/CN) were loaded on g-C3N4 nanosheets with the close loading amounts (similar to 1 wt%) and uniform sizes (2-3 nm). Then, the results of the photocatalytic degradation of ciprofloxacin showed that the generated oxidative active species are highly related to the distribution of palladium valence. Pd2+ (PdO) benefits the production of center dot O-2(-), while Pd-0 benefits the production of h(+). The theoretical simulations revealed that surface states e.g., electron distribution and the adsorption ability of O-2 on different Pd species determined the production of center dot O-2(-) and h(+). Besides, PdO50-Pd50/CN showed the best performance for degrading ciprofloxacin, due to the joint action of center dot O-2(-) and h(+) in the CIP degradation.