Influence of nickel in the hydrogen production activity of TiO2

Abstract

Sol–gel synthesised TiO2 developed by our group was modified through the addition of nickel nitrate and ammonium carbonate in the synthesis process. Photocatalysts were synthesised with different Ni/Ti molar ratios (0.015, 0.030, 0.045) and constant Ni/N ratio equal to 1.5 and subjected to post-calcination at temperatures of between 400 °C and 700 °C. Characterisation was carried out with: X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDX), thermal analysis (TGA, DTA), aggregate size distribution, Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption-desorption isotherm (BET). Photoactivity in terms of photocatalytic hydrogen production was tested using a suspension of photocatalyst at 25 vol.% methanol. With a continuous flow of N2 in headspace the hydrogen produced was conducted to a gas chromatograph for quantification. No evidence of the presence of N was found in the photocatalyst. However, the presence of Ni enhanced TiO2 photoactivity, with a calcination temperature of 550 °C resulting in the highest photoactivity value of 260.76 μmol h−1.