Solar irradiated selective nitroaromatics reduction over plasmonic Ag-TiO2: Deposition time dependent size growth and oxidation state of co-catalyst

Solar irradiated plasmonic Ag-TiO2 (P25) nanocomposites have proficiently harvested solar energy towards nitroaromatics reduction comparatively to almost irresponsive bare TiO2. p-Nitrotoulene (p-NT) and p-nitro-benzaldehyde (p-NBAL) were potentially reduced to p-aminotoulene (p-AT, 87% and 50%) and p-aminobenzaldehyde (p-ABAL, 70% and 38%) with Ag-5-P25 (5 min photodeposition time (PDT)) and Ag 30 -P25 (30 min PDT) respectively. The focus of this study was mainly on the role of PDT (3-30 min) which was found to be directly co-related with size, distribution and oxidation state of deposited Ag nanoparticles (NPs) over titania surface, responsible for superior photocatalytic activity. HR-TEM images confirmed the average size of Ag nanoparticles to be similar to 1-2 nm and similar to 7-8 nm for Ag-5-P25 and Ag-30-P25 respectively. Further, XPS analysis suggested the formation of ternary hybrid (Ag2O/Ag-P25) in case of 5 min PDT whereas only metallic Ag was found to be photodeposited as the times was increased to 30 min.