Green synthesis of nano-silver-titanium nanotube array (Ag/TNA) composite for concurrent ibuprofen degradation and hydrogen generation.

Silver deposited titanate nanotube array composite (Ag/TNA-c) was successfully synthesized using tea leaves and ground coffee as reducing agent for the first time. The synthesis method was effective, eco-friendly, and reproducible in producing quality nano-composite. The Ag/TNA composite was characterized via XPS, SEM, UV-vis, XRD, and electrochemical analyses for chemical and physical properties. Additionally, chlorogenic acid, caffeine, and catechin were selected as reducing agents for purpose of comparison. Results indicated that catechin and chlorogenic acid were the main reducing agents responsible for Ag+ reduction in tea leaves and ground coffee, respectively. The synthesized Ag/TNA-c exhibited the best photocatalytic (PC) performance in terms of photo-current response, EIS, Ibuprofen degradation, and hydrogen generation in a PEC system. Pairing with a Pt cathode, the photoelectrochemical (PEC) system using the synthesized Ag/TNA composite photo-anode, was capable of concurrent anodic oxidation of Ibuprofen and cathodic generation of hydrogen. Deposition of nano-Ag particles on TNA enhanced the concurrent oxidation and reduction reaction in the PEC system. Results of ESR analysis confirmed the role of hydroxyl radical on Ibuprofen degradation over Ag/TNA-c in the PEC system. Mechanism of Ag/TNA PEC system was proposed to illustrate the oxidation and reduction reaction.