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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 KI method by our group [1]. The later involves reduction of Au 3+ ions with iodide ions. XRD results confirmed the formation of CdS hexagonal phase from as prepared cubic phase at 600 °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/cm 2 ). XPS results of Au/CdS prepared by KI 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. [ABSTRACT FROM AUTHOR]