Effect of deposition method on metal loading and photocatalytic activity of Au/CdS for hydrogen production in water electrolyte mixture

Au nanoparticles of size ranging 2-6 nm were deposited over hexagonal CdS using three conventional metal deposition methods namely; deposition precipitation (DP), incipient wet impregnation (WI), photo-deposition (PD) and a recently reported ICI method by our group [1]. The later involves reduction of Au3+ ions with iodide ions. XRD results confirmed the formation of CdS hexagonal phase from as prepared cubic phase at 600 degrees C under the N-2 atmosphere. Transmission electron spectroscopy (TEM), diffused reflectance spectroscopy (DRS), X-Ray fluorescence (XRF), ICP-OES and photoreactions were conducted to study the effect of Au particle size, Au loading and Au plasmonic properties on H-2 production activity. It was found that surface plasmon resonance (SPR) is directly linked to Au particle size. Among all four methods, 3 wt.% Au deposited over hexagonal CdS by KI method with mean Au particle size of 4 nm showed highest performance for hydrogen production from water electrolyte mixture under visible light irradiation (>420 nm and a flux of 35 mW/ cm2). XPS results of Au/CdS prepared by ICI method showed that Au is exclusively present in zero oxidation state before and after photocatalytic H-2 production testes indicating the stable nature of Au/CdS catalyst. The H-2 production activity of Au/CdS catalysts prepared by different metal deposition methods and H-2 production mechanism in a water electrolyte is discussed in detail. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.