Effect of pH and Applied Bias on H2 and HVA Products Through Photoelectrocatalytic Glycerol Oxidation

Abstract

This study explores how pH and applied bias influence the generation of H2 and high-value-added products resulting from glycerol photooxidation, specifically targeting 1,3-dihydroxyacetone (DHA) and glyceraldehyde (GA), within a photoelectrochemical cell. TiO2 NTs with a length of 760 nm were utilized as the photoanode, while Ni foam served as the cathode. The experiments were carried out under acidic, neutral, and alkaline pH conditions, with applied biases ranging from 0.1 to 1 V vs. Ag/AgCl reference electrode. The findings demonstrated that the highest faradaic efficiency towards high-value-added products, namely DHA and GA, was achieved at pH 7 with an applied bias of 0.5 V vs. Ag/AgCl, and this efficiency remained stable at higher bias values. Notably, at pH levels of 2 and 7, both glycerol mineralization into CO2 and H2, and glycerol photooxidation into DHA and GA were more pronounced. Conversely, at higher pH, the faradaic efficiency towards DHA, GA, and CO2 decreased, while the photocurrent increased. This observed trend suggests a heightened water splitting effect at higher pH, leading to a reduction in faradaic efficiency towards H2 due to subsequent reactions with O2 in the gas phase.