Optimized photoactive coatings prepared with functionalized TiO2

Abstract

Functionalization of TiO2 nanoparticles with silane coupling agents was investigated aimed at low-temperature photoelectrode manufacturing for solar driven water splitting application. Different silanes were grafted on the surface of TiO2 in toluene solvent under mild condition. The electrodes were prepared with spin coating by dispersing functionalized particles in DMAc onto FTO glass and dried under vacuum atmosphere at low temperature. UV–Vis spectroscopy of TiO2 powder and its electrodes was studied, and it was found that the spectrum of the modified TiO2 slightly shifted to higher wavelengths. The electrode prepared with functionalized TiO2 showed photocurrent density of up to 0.14 mA cm−2 compared to 0.04 mAcm−2 for pristine TiO2 at 1.23 V, in the water oxidation reaction. The increase in photocurrent density was due to better binding of the TiO2 particles to the substrate resulting in better charge collection observed under SEM. To enhance the photoelectrochemical efficiency, heat treatment was performed and 300 °C was found to be the best heat treatment temperature. The incident photon to current efficiency measurement exhibited an external quantum efficiency up to 4.9% for this heat-treated electrode. Mott-Schottky was plotted to examine the flat band potential. The result showed that the modification resulted in a decrease in the flat band potential suggesting that the charge recombination loss is lower compared to neat TiO2 electrode.