Dual-function silver nanoparticles catalyst supported on ZnO nanoparticles from plant extract: high-TOF hydrogen...

A green hybrid AgNPs@ZnO nanocomposite (NC) was prepared, employing Cyperus scariosus root extract as a natural reducing and stabilizing agent. The prepared nanostructure was thoroughly investigated via UV-vis, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Thermogravimetric Analysis (TGA), and Brunauer-Emmett-Teller (BET) analyses and confirmed the success of Ag deposition and the mesoporous support with considerably increased surface area and stable nature. The dual-functional catalytic activity of AgNPs@ZnO was also tested for hydrogen evolution reaction (HER) at low temperature with Formic Acid (FA) as a hydrogen source and the photo-catalytic degradation of Tetracycline (TC) under solar light. The catalytic dehydrogenation of formic acid (FA) on Ag@ZnO NCs was systematically investigated under various experimental conditions. The catalyst exhibited outstanding efficiency at pH 4 with a TOF of 3935 h^-1 owing to abundant protons and a thermodynamically favorable Ag-ZnO interfacial synergy. The FA/Sodium Format (SF) molar ratio (3 : 1) and the catalyst amount (15 mg) were optimized, whereas water was evaluated as being more effective than DMF or methanol. These results reveal that Ag@ZnO NCs are highly active catalysts for the efficient, selective, and recyclable hydrogen generation from FA under an optimal reaction condition. Photocatalytic degradation of TC was carried out using AgNPs@ZnO, showing an efficient and fast removal (∼99% over 45 min) following pseudo-first-order kinetics, with a low Activation Energy (E _a) value (4.94 kJ mol^-1) and favorable thermodynamic parameters (ΔH = 2.32 kJ mol^-1 and ΔG ≥ 27 kJ mol^-1). The studies of scavenger and band-edge showed that superoxide (˙O₂ ^-) and hydroxyl (˙OH) radicals were major Reactive oxygen species (ROS) in the system, and were enhanced by the synergistic Ag-ZnO effects. The good recyclability of the nano catalyst revealed the potential of NCs for practical applications toward energy and the environment.