Photocatalytic Reactions Using Palladium-Decorated Nanocomposite Materials

Two of the most important environmental issues we face are the cleanup of persistent organic pollutants produced in the past and the development of renewable energy sources for the future. Photocatalysis is a technology that may offer solutions to both problems. Photocatalysts can use light energy, abundantly available in the form of sunlight, to degrade toxic pollutants, and to provide an alternative to fossil fuel-based processes in the production of fine chemicals. Two semiconductor photocatalysts with Pd nanoparticle surface decoration are the focus of this work: Cu₂O@Pd and BiVO₄/BiOBr/Pd. Both materials harness light energy to produce hydrogen from a mixture of ethanol and water; the hydrogen is then activated on the surface of Pd nanodomains and is available to perform chemical transformations. These materials are employed here in the degradation of polybrominated diphenylethers (PBDEs), a class of persistent halogenated organic pollutants, once used extensively as fire-retardant compounds. Of the PBDEs, the one known as BDE-47 (2,2’,4,4’-tetrabromodiphenyl ether) is singled-out for detailed study, due to its prevalence in the environment and its known and suspected harmful effects. This investigation then goes beyond environmental remediation applications and examines the use of BiVO₄/BiOBr/Pd as a catalyst for solar energy-driven hydrogenation of olefins and other organic compounds. Finally, some interesting avenues for further exploration are proposed.