Recent Advances in TiO2-based Photoanodes for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting has attracted a great attention in the past several decades which holds great promise to address global energy and environmental issues by converting solar energy into hydrogen. However, its low solar-to-hydrogen (STH) conversion efficiency remains a bottleneck for practical application. Developing efficient photoelectrocatalysts with high stability and high STH conversion efficiency is one of the key challenges. As a typical n-type semiconductor, titanium dioxide (TiO 2 ) exhibits high PEC water splitting performance, especially high chemical and photo stability. But, TiO 2 has also disadvantages such as wide band gap and fast electron-hole recombination rate, which seriously hinder its PEC performance. This review focuses on recent development in TiO 2 -based photoanodes as well as some key fundamentals. The corresponding mechanisms and key factors for high STH, and controllable synthesis and modification strategies are highlighted in this review. We conclude finally with an outlook providing a critical perspective on future trends on TiO 2 -based photoanodes for PEC water splitting.

In Situ Growth of ZIF-8 Nanocrystals on the Pore Walls of 3D Ordered Macroporous TiO2 for a One-Pot Cascade Reaction

It is wise to mimic a bioinspired system to design a nanoreactor as a catalyst containing multiple components for a cascade reaction. Here, we report the uniform growth of well-dispersed nano-scale ZIF-8 crystals on the pore walls of 3DOM TiO2 via the TEA-assisted crystallization process. The UV-vis spectra indicate that the ZIF-8 photosensitizer can extend the visible-light absorption of 3DOM TiO2. The obtained nanoreactor can efficiently catalyze the one-pot aromatic alcohol oxidization and Knoevenagel condensation cascade reaction for larger molecules. This work offers an important strategy for preparing semiconductor–MOF multifunctional composites with a spatially separated compartmentation for the cascade reaction.