Natural solar light-driven preparation of plasmonic resonance-based alloy and core-shell catalyst for sustainable enhanced hydrogen production: Green approach and characterization

Abstract

Plasmonic Co and/or Ag monometal and their combinations as bimetal alloy and core-shell nanoparticles were prepared under natural sun light, using aqueous glycerol (in-situ reducing agent) and TNP (stabilizer). The formation of bimetallic alloy and core-shell NPs, and their uniform dispersion on the surface of TNP were evidenced by different characterization techniques. Ultraviolet-visible diffuse reflectance spectroscopy evidenced the two distinct characteristic surface plasmon resonance (SPR) absorption bands for the core-shell nanoparticles and a single distinct characteristic SPR band for the alloy. X-ray photoelectron spectroscopy revealed the presence of Ag and Co in the metallic form. The results of H2-temperature programmed reduction of fresh and used samples emphasized the characteristic reduction peaks for the reduction of monometal/bimetal oxide to metallic/bimetallic particles. The interaction of the loaded bimetallic particles with TNP resulted in a shift in the Raman bands. The photoluminescence spectra of the used samples revealed the formation of bimetallic alloy and core-shell structures, which resulted in a decrease in the recombination of charge carriers. X-ray diffraction, electron paramagnetic resonance spectroscopy, high-resolution transmission electron microscopy, and cyclic voltammetry analyses substantiated the same. The monometal-loaded photocatalysts and the bimetal alloy and core-shell nanoparticle-loaded photocatalysts were further examined for H2 production with pure water/aqueous glycerol/crude glycerol under natural solar light irradiation. The (Ag-Co)coloadedTNP catalyst yielded the maximum H2 evolution rate of 63 mmol g−1. For comparison, experiments were conducted under artificial solar light irradiation with similar experimental conditions. Based on the results, different mechanistic paths for insitu photoreduced Ag-Co bimetallic alloy and core-shell nanoparticles on TNP for H2 production are envisaged.