The development of sustainable materials capable of capturing and transforming solar energy into green chemical fuels has become of great interest in the last years. Several semiconductors have been studied for this application and the search for the ideal material continues. It is becoming increasingly evident that a single material will not be able to fully satisfy all the requirements needed to produce a practical device. Therefore, nanocomposites, where two or more compounds are combined in a new material at the nanoscale, are an interesting starting point towards the design of integrated systems for solar fuels production. In this work we present the synthesis of mesoporous TiO2 thin films prepared via a sol-gel approach. These films can be easily modified with a cobalt catalyst (CoPi). We studied the effect of the catalyst loading on the photoelectrochemical water splitting efficiency. The results show that these systems present two regimes: at low potentials (<1.5 V vs RHE) the catalyst mainly reduces the photocurrent densities probably due to increased recombination at the TiO2/CoPi interface, while at high applied potentials (> 1.5 V vs RHE) water oxidation is enhanced due to the intrinsic electrocatalytic activity of CoPi. These results open new questions to understand the interplay between the components in these type of composite nanosystems.

Mesoporous TiO2 photoelectrodes for water splitting: effect of Co catalyst deposition

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