Thermo-responsive functionalized PNIPAM@Ag/Ag₃PO₄/CN-heterostructure photocatalyst with switchable photocatalytic activity

It is extremely important for photocatalysts to exhibit intelligent responsiveness to their environment. Herein, a poly N-isopropyl acrylamide (PNIPAM)-modified Ag/Ag₃PO₄-20/CN hybrid material with excellent convertible photocatalytic activity is prepared. PNIPAM has good hydrophilicity below the lower critical solution temperature (LCST); this increases the capacity of the photocatalyst for adsorbing tetracycline (TC) molecules. In addition, the PNIPAM-modified Ag/Ag₃PO₄-20/CN can prevent the loss of Ag₃PO₄. The dispersity is improved by loading g-C₃N₄ nanosheets (CN) for enhancing the efficiency of photocatalytic activity. Furthermore, a Z-scheme heterostructure is formed between CN and Ag₃PO₄, accelerating the separation efficiency of the holes and electrons. Ag nanoparticles can be used as electron-shuttle mediators, and electrons receiving more energy are transferred via the localized surface plasmon resonance (LSPR) effect. Furthermore, the PNIPAM@Ag/Ag₃PO₄-20/CN photocatalyst exhibits an excellent degradation rate for the degradation of TC when the temperature is lower than the LCST. The photoluminescence spectra and photocurrent curves prove that the carrier-separation efficiency of PNIPAM@Ag/Ag₃PO₄-20/CN is higher than those of Ag/Ag₃PO₄/CN and CN. The main active species of ·O₂⁻ and h⁺ are detected to reveal the plausible mechanism of the PNIPAM@Ag/Ag₃PO₄-20/CN hybrid material system. This work provides a way to develop intelligent materials for switchable photocatalytic applications.