Synergy of Adsorption and Plasmonic Photocatalysis in the Au-CeO 2 Nanosystem: Experimental Validation and Plasmonic Modeling

• Published in: Langmuir 2022-06, Vol.38 (24), p.7628-7638
• Main Authors: Nath, Manash P, Biswas, Sritam, Nath, Pabitra, Choudhury, Biswajit
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.2c01056

Adsorption-mediated water treatment leaves adsorbents as secondary pollutants in the environment. However, photocatalysis aids in decomposing the contaminant into its nontoxic forms. In this context, we demonstrate an adsorption-photocatalysis pairing in Au-CeO nanocomposites for a total methylene blue (MB) removal from water. We synthesized Au-CeO through the citrate ( ) reduction method at different Au loading and studied its adsorption capacity with kinetics and thermodynamic models. We observe that the high adsorption capacity of Au-CeO is primarily because of the presence of Ce states in CeO and citrate ligands on Au NPs. The Ce states interact and transfer their electrons to supported Au NPs, rendering a negative charge over Au. The negatively charged Au surface and the carboxyl (-COO ) group of citrate ligands mediate an electrostatic interaction/adsorption of cationic MB. The total removal of MB is expedited under white light and lasers. A control experiment with Au NPs shows less adsorption-photocatalysis. The size of Au NPs and Au-CeO interfacial interaction is responsible for the surface plasmon resonance spectral position at 550-600 nm. Linear sweep voltammetry (LSV) and plasmonic field simulation show surface plasmon-driven photocatalysis in Au-CeO . LSV shows a 3-fold higher photocurrent density in Au-CeO than colloidal Au NPs under white light. The simulated electric field intensity in Au-CeO is maximum at SPR excitation and the closest interfacial separation ( = 0 nm). The plasmon-driven photocatalysis in colloidal Au NPs is mainly due to the interaction of hot electrons with the adsorbed MB molecule. Notably, near-field light concentration, hot electrons, and interfacial charge separation are responsible for excellent MB removal in the Au-CeO nanosystem. The total MB removal through adsorption-photocatalysis pairing is 99.3% (Au-CeO ), 30.7% (Au NPs), and 13% (CeO ).