Kinetic study of the effects of pH on the photocatalytic hydrogen production from alcohols

Solution pH is an important parameter in photocatalytic reactions that substantially affects the process by changing photocatalyst agglomeration and substrate adsorption on photocatalyst surface. In this work, a kinetic study was performed on photocatalytic hydrogen production from alcohols and an intrinsic kinetic model was developed to predict the rate of hydrogen production from different alcohols as a function of pH. Glycerol, ethanol, and methanol were selected as representative substrates and tested in a pH range of 2-12. The very good agreement between model predictions and experimental data was confirmed by statistical analyses (R-2, R-adj(2), RMS, AAD, and MAE). The results revealed that for all substrates investigated, the maximum hydrogen rate was obtained at a pH similar to 8. A local minimum for hydrogen production was observed around pHzpc, as a result of catalyst agglomeration. The results of this study can be very useful in future investigations of the effects of pH on other aqueous phase photocatalytic processes. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.