Photoelectrochemical glyoxylates and hydrogen production from polyethylene terephthalate wastes using BiVO4 anode with dominant (040) facets

In this study, the oxidation reaction of ethylene glycol (EGOR) for hydrogen production is investigated in a photoelectrochemical configuration to reduce the energy barrier in water splitting. For this, BiVO₄ photoanode with exposed (040) facets is synthesized and with increase of the constitution of (040) facets, the onset potential for EGOR is reduced to 0.215 V (vs. RHE), the photocurrent density is 3.55 mA cm⁻² at 0.5 V in N₂-saturated EG-containing alkaline electrolyte (vs. RHE). Cyclic voltammetry is then performed in the potential window from 0.5 V to −0.3 V (vs. RHE) in N₂-saturated PET plastic alkaline solution, where hydrogen evolution rate reaches 1.41 μmol cm⁻² h⁻¹, making a 7.4-fold increase compared to the flat BVO. Notably, in this potential window, the oxidation products are identified to be glyoxal and glyoxylate, with production rates of 61.6 and 134.7 μmol cm⁻² h⁻¹, respectively. (040) Facet of BVO plates is thermodynamically favourable for EGOR by DFT calculations, and such configuration allows for high active surface area and fast charge transfer kinetics. This work thus offers valuable insights on upcycling of PET wastes utilizing abundant metal oxide photoelectrodes via a sustainable approach.