Bifunctional Pd-Al:SrTiO₃ photocatalyst sheet for m²-scale waste PET photoreforming and feasibility study

Photocatalytic reforming of waste plastics offers a route towards a circular plastics economy and sustainable energy generation by producing commodity chemicals and green H₂ while mitigating plastics accumulation in the environment. As a monomer of polyethylene terephthalate (PET), a dominant waste plastic, ethylene glycol (EG) has gained attention as a promising substrate for reforming processes, but photocatalytic EG oxidation suffers from low product selectivity, slow reaction rates, and poor stability due to the limited availability of efficient cocatalysts. Here, a bifunctional Pd nanoparticle cocatalyst is introduced on an Al-doped SrTiO₃ (Al:SrTiO₃) semiconductor to simultaneously promote EG oxidation and H₂ evolution reactions. Considerations for Pd utilisation at scale in photocatalytic technologies is supported by its projected increase in availability. The Pd-decorated Al:SrTiO₃ system was coated onto glass substrates to fabricate scalable photocatalytic sheets for a 1 m²-scale outdoor demonstration of waste PET bottle reforming. In three days of continuous operation under natural sunlight, 48, 45, 19 and 3 mmol m^-2 of H₂, formate, glycolate and glycolaldehyde, respectively, were produced. A comprehensive feasibility study was performed based on this prototype waste PET reforming system to identify key areas to prioritise in future research. Although photocatalytic reforming was unsurprisingly found to be premature for practical application, reactor cost and photocatalyst stability were identified as critical issues to realise a feasible large-scale system in the future. This work presents a robust bifunctional photocatalyst system and provides a systematic feasibility assessment of large-scale PET reforming.