Photoreforming of PET and PLA microplastics for sustainable hydrogen production using TiO2and g-C3N4photocatalysts

Abstract

Photoreforming of polyethylene terephthalate (PET) and polylactic acid (PLA) microplastics has been investigated as a sustainable approach for hydrogen evolution. Thermodynamic analysis confirmed the feasibility of hydrogen evolution during the degradation of PET and PLA under UV irradiation (254anm). Photolysis experiments in water demonstrated that hydrogen, methane, and carbon monoxide were the primary gaseous products. PLA yields higher amounts of hydrogen than PET. The presence of NaOH significantly reduced hydrogen evolution, likely because of the scavenging of hydrogen radicals with hydroxide ions and neutralisation of carboxylic groups. Photocatalytic experiments in water using TiO2 and graphitic carbon nitride (g-C3N4) further increased the hydrogen yields of PET and PLA, with a more pronounced effect on PLA. However, in NaOH suspensions, hydrogen evolution increased only for PLA in the presence of TiO2, while g-C3N4 had no effect. This was attributed to the instability of g-C3N4 under alkaline conditions, as confirmed by the structural analysis.