Methanol, ethylene glycol, and glycerol photoelectrochemical oxidation reactions on BiVO4: Zr,Mo/Pt thin films: A comparative study

Abstract

The green H₂ production plays a key role in the energy transition, however it still needs improvements to be applied in a large scale. The water oxidation reaction, as an anodic process to provide both protons and electrons for H₂ production, possesses kinetic limitations. Therefore, the use of an alternative process like the oxidation of biomass-derivative species is extremely desired to replace water oxidation during H₂ production. In this work, we provide a comparative study of different small organic molecules (methanol, ethylene glycol (EG), and glycerol) as alternatives to water oxidation at pristine BiVO₄, Mo-Zr dopped BiVO₄, and Pt co-catalyst BiVO₄ photoanodes in neutral media. While the band energy diagram and surface morphology are similar for the distinct materials, the presence of Zr-Mo increases the charge carriers density. The presence of Pt acts as co-catalyst for the organic molecules. Regardless of the material employed, the activity order for each organic molecule reaction was: j_water < j_methanol < j_EG < j_glycerol affeered by both linear potential sweep and chronoamperometry at 1.23 V vs RHE. The presence of both Zr-Mo and Pt increases the photoactivity for the alcohol's oxidation, however the presence of Pt is more advantageous for glycerol oxidation than for other species, maintaining 80 % of activity after 24 h electrolysis. The reactivity of alcohols can be tentatively explained by the greater stability of radicals formed from larger molecules.