Rational design of graphite carbon nitride-decorated zinc oxide nanoarrays on three-dimensional nickel foam for the efficient production of reactive oxygen species through stirring-promoted piezo-photocatalysis.

Stirring-promoted piezo-photocatalysis based on a three-dimensional foam architecture has great potential applications in wastewater treatment and water splitting. However, the detailed mechanism of stirring-promoted piezo-photocatalysis has not been quantitatively studied, and the utilization of visible light needs to be further improved. In this work, the high solar-driven piezo-photocatalytic ability of graphite carbon nitride (g-CN)-decorated zinc oxide (ZnO) nanoarrays on nickel (Ni) foam is experimentally achieved and first simulated by the finite element method (FEM). The water flow velocity, depending on the stirring rate, is significantly increased by turbulence-induced fluid eddies while flowing through 3D macropores and nanoarrays, resulting in higher piezoelectricity. Reactive oxygen species (ROS) are experimentally examined by the electron spin resonance (ESR) technique and theoretically calculated by density functional theory (DFT) to confirm the configurations of the heterojunction under photocatalysis and piezo-photocatalysis. In particular, the large enhancement of O generation suggests the potential of piezo-photocatalysis in biological applications. The mechanism of piezo-photocatalysis is proposed in which the S-scheme heterojunction is realized by piezoelectricity to improve photocatalysis by retaining high redox ability and inhibiting recombination. This work provides a possible approach to harvesting energy sources for piezoelectricity and expands the scope of solar-driven piezo-photocatalysis.