A cascading gradient pore microstructured photoanode with enhanced photoelectrochemical and photocatalytic activities

In this work, a novel photoanode with a cascading gradient pore microstructure is proposed to enhance photoelectrochemical and photocatalytic activities, which consists of a nanocrystalline TiO 2 layer synthesized by the sol–gel method, a microporous layer, and a macroporous layer formed by adding PEG and PMMA as the template, respectively. The gradient pore microstructure can not only enhance the mass and photon transfer and improve the light utilization, but also increase the electrical conductivity and restrain the recombination of photoexcited electron–hole pairs. Furthermore, the cascading design helps to establish tighter interparticle connections between layers. Because of these merits, it has been found that the cascading gradient pore microstructured photoanode exhibited a 63% improvement over the conventional photoanode in terms of photoelectrochemical activity. This new design also enhanced the photocatalytic activity, leading to a much higher methylene blue degradation efficiency (76.7%) than that of conventional photoanodes (62.5%). The effect of the PMMA/TiO 2 ratio on the structure and performance of the proposed photoanode was also investigated. The highest performance was achieved with a PMMA/TiO 2 ratio of 1:1. The obtained results establish a new avenue for designing the photoanodes of photoelectrochemical systems.