Photoreforming of PET and PLA microplastics for sustainable hydrogen production using TiO2 and g-C3N4 photocatalysts

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 (254 nm). 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 TiO 2 and graphitic carbon nitride (g-C 3 N 4 ) 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 TiO 2 , while g-C 3 N 4 had no effect. This was attributed to the instability of g-C 3 N 4 under alkaline conditions, as confirmed by the structural analysis. • The photoreforming of PET and PLA microplastics under UV light has been studied. • The photoreforming was performed by photolysis and photocatalysis • Hydrogen was the main photoreforming product along with CO and CH 4 . • Higher hydrogen yields were obtained from the water suspensions of PLA.