Photocatalytic H2 production from ethanol(aq) solutions: The effect of intermediate products

The production of H2 via the photocatalytic transformation of aqueous solutions of ethanol, over Pt/anatase was studied in a semi-batch reactor. High H2/COx ratios were obtained indicating that the photoreforming of ethanol only occurred in a small proportion of the ethanol. The main products detected in the liquid phase after the photocatalytic conversion of ethanol solutions were acetaldehyde, acetic acid and 2,3-butanediol, with acetaldehyde being the most abundant. The photoreaction of acetaldehyde(aq), acetic acid(aq) or 2,3-butanediol(aq) resulted in lower amounts of H2 compared with that of ethanol(aq). The main reaction pathway for the photocatalytic transformation of acetaldehyde(aq) is via the formation of acetic acid and H2. Then, CO2 and CH4 are formed from the decomposition of acetic acid(aq). The decrease in the H2 production rate during the photocatalytic reforming of ethanol solutions is related to the presence of the intermediate products formed in the liquid phase that are not removed from the reaction medium. Carboxylate species and metallic Pt were present on the surface of the post-reaction catalyst.