Mechanistic analysis identifying reaction pathways for rapid reductive photodebromination of polybrominated diphenyl ethers using BiVO ₄/BiOBr/Pd heterojunction nanocomposite photocatalyst

Abstract

BDE-47, a significant environmental pollutant, is rapidly and completely debrominated to diphenyl ether using the nanocomposite photocatalyst, BiVO ₄/BiOBr/Pd. Mechanistic details of the degradation pathway are probed.

Abstract

Polybrominated diphenyl ethers (PBDEs), previously incorporated in a wide variety of common products, can now be found throughout the environment. Because of their environmental persistence and the potential health hazards they pose to humans and wildlife, they have been added to the Stockholm Convention on Persistent Organic Pollutants, and they continue to be of significant concern. We report herein the first application of a nanocomposite catalyst consisting of a m-BiVO ₄/BiOBr heterojunction surface-decorated with Pd nanoparticles in the photocatalytic reductive debromination of PBDEs using visible light. Specifically, this system demonstrated both rapid and complete debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), with an exceedingly large initial pseudo-first-order rate constant of 1.33 min ⁻¹. Analysis of the reaction mechanism identified the stepwise degradation pathway to generate the final diphenyl ether product as well as the role of the alcohol-based sacrificial reagent. Such information provides routes towards new approaches for environmental remediation by identifying reaction pathways for common organic pollutants that remain challenging to degrade via sustainable methods.