Biomass-Derived Compounds Photoelectrolysis in PGM-Free Continuous Flow Cells for the Simultaneous Production of Hydrogen and Valuable Chemicals

This study explores the reforming of biomass-derived compounds, namely, glycerol, glucose, and fructose, in a continuous photoelectrocatalytic cell utilizing PGM-free electrodes, specifically TiO2 nanotubes (NTs) photoanodes for selective oxidation and a Ni foam cathode. TiO2 NTs with varying structural characteristics were grown on Ti felt through an anodization process, followed by annealing to promote crystallization. Notably, in this study, photoelectrolysis of glucose and fructose was investigated for the first time in a continuous PEC cell. These electrodes were tested in acidic aqueous solutions (pH = 2) without and with biomass-derived compound addition. In their presence within the reaction mixture, hydrogen production occurred simultaneously with the formation of valuable partial oxidation compounds─dihydroxyacetone (DHA) and glyceraldehyde (GA) from glycerol and gluconic acid (GluA) and formic acid (FA) from glucose or fructose─achieving faradic efficiencies (FEs) of 13, 53, 54, and 18%, respectively. Compared to previous studies, the continuous cell employed in this study allowed for significantly higher FEs and high value-added production rates, demonstrating an enhanced utilization of photogenerated holes for selective biomass-derived compounds oxidation. Additionally, the photoanodes and the cathode exhibited excellent mechanical and chemical stability, maintaining performance over time and allowing for their reuse for numerous cycles after a simple cleaning step. These results highlight the potential of this photoelectrocatalytic process for both biomass-derived compound valorization and hydrogen production.