Palladium–Copper Alloy Nanoparticles Supported on Carbon Nitride Nanosheets as a Photocatalyst for Degradation of Ciprofloxacin

Optimization regarding the electronic structure of nanometal cocatalysts via alloying is considered as a promising strategy to regulate the formation of reactive oxygen species (ROS) in photocatalytic degradation. Herein, a series of g-C3N4-supported PdCu alloy cocatalysts were constructed to investigate the regulatory effect and mechanism of alloying on photocatalytic active species. Photocatalytic degradation experiments using ciprofloxacin (CIP) as a model pollutant demonstrated that optimal alloying with PdCu (Cu ≤ 0.5 wt %) significantly boosts the production of active species and incrementally enhances the contribution of superoxide anions (·O2–). The introduction of Cu leads to the redistribution of surface electrons in the PdCu alloy, resulting in a gradual strengthening of the O2 adsorption as the Cu content increases up to 0.5 wt %. The CIP degradation rate reaches a maximum of 80.5% at pH 6.7. Inorganic ions such as Na+ and Ca2+ inhibit degradation, while low concentrations of Fe3+ promote that. The CIP degradation rate in actual water samples ranges from 71.1 to 78.2%. Furthermore, the degradation pathway initiated from carbonyl destruction induced by a higher ·O2– concentration was proposed. This comprehensive study provides valuable insights into the design of alloyed photocatalysts, emphasizing the significance of optimizing metal composition to regulate ROS generation and enhance photocatalytic efficiency.