Self-powered photoelectrochemical quartz/TiO2 microsystem through piezopotential sensitized photocatalytic process

Abstract

A self-powered photoelectrochemical microsystem comprising quartz prism microrods assembled with TiO2 nanoparticles (NPs; quartz/TiO2) is developed and demonstrates a marked catalytic effect on organic dye degradation and hydrogen evolution through a piezopotential sensitized photocatalytic process (referred to as synergistically piezophotocatalytic processes or piezophototronics herein). The results of piezoresponse force microscopy (PFM) and the electrical output of the piezoelectric nanogenerator suggest that the quartz microrods act as a self-powered bias subjected to mechanical stress that can produce an additional electric field around the surrounding TiO2 NPs. With the finite element method, the simulation results indicate that the interfacial stress effect between the two materials plays a vital role in enhancing piezoelectric potential (piezopotential). The reaction rate constant (kobs) for the dye degradation of the quartz/TiO2 heterostructure reaches 0.0624 min−1 under a piezophototronic effect, approximately 2.2 times greater than that for photocatalysis (rate constant kobs = 0.0281 min−1). Additionally, hydrogen production reaches 438.48 µmol·g−1·h−1 through the synergistic piezophototronic effect, a 225% increase when compared with that of pristine quartz. This improvement is attributable to mechanical force–induced piezoelectric polarization, which acts as an internal bias modulating the TiO2 band structure and ejecting the photogenerated electrons and holes in opposite directions, thereby retarding recombination behaviors and facilitating redox reactions.