Unraveling photoexcited electron transfer pathway of oxygen vacancy-enriched ZnO/Pd hybrid toward visible light-enhanced methane detection at a relatively low temperature

In this work, we present a novel CH4 oxidation photocatalyst based on oxygen vacancy-enriched ZnO nanorods/Pd nanoparticles hybrid (OV ZnO/Pd), which could be incorporated into a high-performance photocatalysis-enhanced CH4 sensor operating under visible light illumination at a relatively low temperature. By introducing visible light illumination, the CH4 response of the sensor based on OV ZnO/Pd was enhanced by 6 times compared to that in the dark. The CH4 sensing performance was found to be directly related to the photocatalytic CH4 oxidation activity of the sensing materials. O-2 temperature-programmed desorption analysis and in-situ FT-IR spectroscopy suggested the synergistic effect of oxygen vacancies and Pd nanoparticles on promoting the surface oxygen activation and catalytic CH4 oxidation over the OV ZnO/Pd hybrid. Photoelectrochemical measurements revealed a new photoexcited electron transfer pathway in the hybrid, which involved the direct transfer of hot electrons from Pd nanoparticles to the surface oxygen vacancies on ZnO.