Lastly, theresulting powder was reduced with H2for 2 h at 573 K and then oxi-dized by air for 1 h at 473 K to form a core-shell structure of Ni/NiOcluster.Pt/WO3catalyst was prepared by a photo-deposition process.Firstly, H2PtCl6solution of desired concentration was mixed withcommercial WO3(Aldrich 99.995%) powder to give a 0.5 wt.%of Pt-loaded. The well-mixed solution was next irradiated byUV lamp with an intensity of 5 W/cm2for 1.5 h to perform thephoto-deposition process. The resulting powder was subsequentlywashed by de-ionized water and centrifuged several times toensure that there was no residual Cl−remaining on the photocata