Electrochemical Doping as a Way to Enhance Water Photooxidation on Nanostructured Nickel Titanate and Anatase Electrodes

A number of metal oxides have been proposed as useful materials for the photoelectrochemical (PEC) production of hydrogen from water. However, up to now, an ideal standalone material has not been found. We have investigated the possible use of nickel titanate (NiTiO3) nanorods as a photoanode. Although these electrodes absorb visible light, they show a modest PEC behavior. Interestingly, the photocurrent for water oxidation undergoes a 30-fold enhancement after an optimized reductive electrochemical pretreatment. Here, the induced doping is studied and compared with the corresponding for anatase nanoporous electrodes. The results reveal the key role of the electrolyte pH as well as the size of the electrode building blocks. The photocurrent promotion upon the electrochemical pretreatment can be ascribed to an enhanced charge transport linked to the ability of proton insertion in the crystal structure.