DEVELOPMENT OF Cu-Ni/TiO2 BIMETALLIC CATALYST FOR PHOTOHYDROGEN PRODUCTION UNDER VISIBLE LIGHT ILLUMINATION

• Main Author: ELA, ELA NURLAELA
• Format: Thesis
• Language: English
• Published: 2011
• Online Access: http://utpedia.utp.edu.my/2796/1/Ela_Thesis.doc; http://utpedia.utp.edu.my/2796/

Photocatalytic hydrogen production from water using TiO2 as photocatalyst is one of the most promising method to produce hydrogen due to its low cost and environmental friendly process. However, it lacks the efficiency which is required in order to be economically feasible. This study is focused on enhancing the activity of TiO2 to utilize visible light by Cu-Ni incorporation onto its surface, and also improving the overall photocatalytic hydrogen production by the addition of sacrificial agent. The incorporation of Cu-Ni onto TiO2 was achieved by employing precipitation method and parameters such as calcination temperature and duration, Cu:Ni mass composition, and total metal loading were studied. The physical and chemical properties of the modified photocatalysts were investigated using Thermogravimetric Analysis (TGA), Fourier-Transformed Infrared Spectroscopy (FTIR), Field-emission Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (FESEM-EDX), Diffuse Reflectance UV-Vis Spectroscopy (DRUV-Vis), Surface area and porosity analysis, Temperature-programmed Reduction (TPR), and powder X-ray Diffraction (XRD). Morphology of the photocatalyst particle was spherical with slight agglomeration and high metal dispersion was achieved which was confirmed by XRD and FESEM-EDX analyses. It is believed that monometallic Cu/TiO2 and Ni/TiO2, and bimetallic Cu-Ni/TiO2, were in their oxide form. The presence of Cu-Ni mixed oxide was detected by TPR analysis although it was not confirmed by XRD analysis due to the high metal dispersion. DRUV-Vis characterization showed that incorporation of Cu, Ni, and Cu-Ni onto TiO2 shifted the absorption edge into visible region thus reducing the bandgap energy. The surface area of photocatalysts was found to be increased higher than that of bare TiO2. In addition, the Cu-Ni/TiO2 photocatalysts were studied for photocatalytic hydrogen production under visible light illumination from two reaction media: distilled water (H2O), and mixture of distilled water and glycerol (H2O+gly). The photocatalytic study revealed that incorporation of Cu-Ni greatly enhances the photocatalytic activity of TiO2. The highest amount of hydrogen evolved was 6.1 mL, three times higher compared to that obtained using bare TiO2. 10wt%_9Cu1Ni_200_1, 10wt% metal loading photocatalyst with 9:1 of Cu:Ni mass composition, calcined at 200 oC for 1 h, was found as the best photocatalyst. The addition of glycerol (H2O+gly) as sacrificial agent increased the amount of hydrogen evolved almost 1.5 times higher compared to that in (H2O). The value added product as intermediates of glycerol oxidation such as glyceraldehyde, glycolic acid, and oxalic acid were also detected. The kinetics study also showed that the addition of glycerol addition enhanced the rate of photocatalytic reaction. The values of apparent rate constant (k) for photocatalytic hydrogen production from (H2O) and from mixture of (H2O+gly) were 0.3195 g0.84L0.16min-1 and 0.3989 g0.805L0.195min-1, respectively. On the other hand, the reaction order (n) with respect to photocatalyst amount were 0.160 and 0.195, for photocatalytic hydrogen production from distilled water (H2O) and from mixture of water and glycerol (H2O+gly), respectively.