Efficient interfacial charge transfer through plasmon sensitized Ag@Bi2O3 hierarchical photoanodes for photoelectrocatalytic degradation of chlorinated phenols

Abstract

The present work demonstrates an extremely proficient and robust study of efficient interfacial charge transfer through plasmonic Ag decorated Bi₂O₃ hierarchical photoanodes for the photoelectrochemical treatment of chlorinated phenols. Unique 2D flake-like Bi₂O₃ hierarchical nanostructures were grown onto a fluorine-doped tin oxide (FTO) substrate by a simple chemical bath deposition method using triethanolamine as complexing agent. The formation of Bi₂O₃ on FTO was governed by the decomposition of a nucleated bismuth-hydroxyl complex (Bi₂O_1−x(OH)_x) and modification to the electrode was carried out by the deposition of Ag via a chemical reduction method using hydrazine hydrate. Both the fabricated electrodes were well characterized for their photo- and electro-optical properties. Efficient charge separation was observed due to the surface plasmon resonance phenomenon of silver nanoparticles with the favorable intrinsic properties of Bi₂O₃ under application of a small electric bias of 1 V preventing the recombination of charge carriers and thereby increasing the rate of photoelectrocatalytic degradation of the chlorinated phenols. PEC degradation using the Ag@Bi₂O₃ photoelectrode followed the trend 4-CP < 2,4-DCP < 2,4,6-TCP < P-CP due to efficient attack at the chlorinated positions by reactive oxygen species with increasing chlorine substitution and also due to the absence of an expected chain reaction of the generated chlorine radicals (Cl˙) during the PEC reaction. The PEC activity of Ag@Bi₂O₃ was 1.5 times higher than a Bi₂O₃ nanoflake electrode for 4-CP over 2 h. The fabricated Ag@Bi₂O₃ proved to be an efficient photoelectrode with synergistic solar-induced photoactivity. A detailed mechanistic study in the presence of scavengers suggests degradation by produced hydroxyl radical species. Thus, physical insights into the degradation of chlorinated phenols were obtained.