Mesoporous TiO<sub>2</sub>: Comparison of Classical Sol−Gel and Nanoparticle Based Photoelectrodes for the Water Splitting Reaction

This paper describes a systematic comparison of the photoelectrochemical properties of mesoporous TiO<sub>2</sub> films prepared by the two most prevalent templating methods: The use of preformed, crystalline nanoparticles is generally considered advantageous compared to the usage of molecular precursors such as TiCl<sub>4</sub>, since the latter requires a separate heat treatment at elevated temperature to induce crystallization. However, our photoelectrochemical experiments clearly show that sol−gel derived mesoporous TiO<sub>2</sub> films cause an about 10 times higher efficiency for the water splitting reaction than their counterparts obtained from crystalline TiO<sub>2</sub> nanoparticles. This result indicates that for electrochemical applications the performance of nanoparticle-based metal oxide films might suffer from insufficient electronic connectivity.