EFFECTS OF SURFACE ETCHING ON THE STRUCTURE AND PERFORMANCE OF RH2O3 CDS CATALYST/

The effect of heat treatment at high temperature and etching with acet ic acid on the composition, oxidation state and photoactivity of RhOx/ CdS catalysts was investigated. Our results indicate that heat treatme nt at high temperature is a crucial step in the enhancement of the pho tocatalytic activity of RhOx/CdS catalysts, and they confirm the oxida tion of RhCl3 into Rh2O3 during heat treatment at 773 K in air (Xray d iffraction (XRD) and X-ray photoelectron spectroscopy (XPS) observatio ns). Our results also indicate the formation of CdO, CdSO4 and CdCl2 d uring treatment at 773 K and their removal by washing with acetic acid solution at pH 4.5, The photoactivity results reveal that the pretrea ted catalyst exhibits a much higher activity for hydrogen generation f rom H2S decomposition and methanol dehydrogenation on visible light ir radiation. CdO shows no photoactivity regardless of the method used to prepare the catalyst. No evidence of Cd(OH)(2) or Rh2S3 formation was found in our investigation, XPS data suggest that there is a strong i nteraction between Rh2O3 and CdS after heating at 773 K. The possible mechanism of enhanced photocatalytic activity is discussed.