Microwave-Assisted Synthesis of Ag-Decorated TiO2 Nanotubes for Photocatalytic Hydrogen Evolution

Abstract

Microwave (MW)-assisted aqueous synthesis of nanostructures offers an environmentally friendly alternative that aligns with green chemistry principles. In this study, we report the synthesis of silver nanoparticles (AgNPs) using a standard commercial MW oven and an aqueous extract of fresh cassava root, which served simultaneously as solvent and reducing/stabilizing agent. TiO2 nanotubes (NTs), synthesized via a MW digestion system, were impregnated with the as-prepared AgNPs, and their photocatalytic activity was evaluated for hydrogen generation. The physicochemical properties of the synthesized AgNPs were characterized using various techniques, including FTIR, HAADF-STEM, UV–visible (vis)DRS, RBS, and XPS. The average diameter of the AgNPs impregnated on TiO2 NTs, as measured by HAADF-STEM, was (1.7 ± 0.2) nm. Increasing the AgNO3 concentration led to the formation of larger particles with a broader size distribution. Incorporation of very small AgNPs into TiO2 NTs resulted in a significant enhancement of the hydrogen evolution rate during methanol photoreforming at room temperature, increasing from 2.45 µmol g−1 h−1 for pristine TiO2 NTs to 4.1 µmol g−1 h−1. Reports on the use of green AgNPs prepared by MW-assisted irradiation in hydrogen photogeneration experiments remain scarce in the literature, suggesting promising opportunities for advancing sustainable energy applications.