Photocatalytic production of ethylene and propionic acid from plastic waste by titania-supported atomically dispersed Pd species

Abstract

Current chemical recycling of bulk synthetic plastic, polyethylene (PE), operates at high temperature/pressure and yields a complex mixture of products. PE conversion under mild conditions and with good selectivity toward value-added chemicals remains a practical challenge. Here, we demonstrate an atomic engineering strategy to modify a TiO 2 photocatalyst with reversible Pd species for the selective conversion of PE to ethylene (C 2 H 4 ) and propionic acid via dicarboxylic acid intermediates under moderate conditions. TiO 2 -supported atomically dispersed Pd species exhibits C 2 H 4 evolution of 531.2 μmol g cat −1 hour −1 , 408 times that of pristine TiO 2 . The liquid product is a valuable chemical propanoic acid with 98.8% selectivity. Plastic conversion with a C 2 hydrocarbon yield of 0.9% and a propionic acid yield of 6.3% was achieved in oxidation coupled with 3 hours of photoreaction. In situ spectroscopic studies confirm a dual role of atomic Pd species: an electron acceptor to boost charge separation/transfer for efficient photoredox, and a mediator to stabilize reaction intermediates for selective decarboxylation.