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CoO–MoO3/Al2O3catalysts with different contents of citric acid were prepared by the simultaneous impregnation method and were tested for sulfur-resistant methanation. The catalysts were characterized with N2-physisorption, XRD, scanning electron microscopy (SEM), H2-TPR, Raman spectroscopy, ultraviolet–visible spectroscopy, and XPS. The N2-physisorption and SEM results indicated that the addition of citric acid could increase the BET surface area and the amount of smaller particles in catalysts, improving the monolayer loading capacity. It would result in the better dispersion of metal active components (Co, Mo species). The combined results of various characterization suggested that the addition of citric acid could avoid the formation of crystalline CoMoO4while the Mo–CA complex was found in the Raman spectrum. As the mole ratio of n(CA)/n(Mo) increased up to 2.0, the catalysts showed the highest activity in sulfur-resistant methanation as there were the most MoS2on the surface of Al2O3supports according to the results of XPS.

Efficient and visible-light responsive CuO/TiO2photocatalysts were fabricated by six methods: simple wet impregnation (SWI), ethanol impregnation (EI), stepwise impregnation (SI), in situ sol–gel (SG), chemical adsorption decomposition (CAD), and composite precipitation (CP). The prepared CuO/TiO2composites were characterized using X-ray diffraction, nitrogen adsorption desorption isotherms, transmission electron microscopy, UV–Vis diffuse reflectance spectra, and H2-temperature programmed reduction. Due to the different preparation processes, the hydrogen evolution rate from water splitting on the as-prepared CuO/TiO2nanocomposites was recorded. The results showed that the photocatalytic hydrogen evolution rate decreased in the sequence of CAD sample > CP sample > EI sample > SWI sample > SI sample > SG sample. The hydrogen evolution rate of the CAD sample was proved to be the highest among the samples and reached 3155.7 μmol/(g·h), which was 2.46 times larger than that of SG sample. In addition, the stability of the CAD sample and the EI sample was compared. The addition of copper could efficiently suppress the recombination of electron/hole pairs in titanium dioxide, improve the transfer of interfacial charge, enhance visible-light adsorption and provide plentiful photocatalytic reaction active sites.