No abstract

No abstract

No abstract

No abstract

We have studied the gas phase H 2 production by methanol thermo-photoreforming using Cu-modified TiO 2 . Metal cocatalyst has been deposited by means of photodeposition method. The concentration of methanol in the steam was also considered. It appears that H 2 production is notably higher as temperature increases. Moreover, the optimum H 2 yield is achieved using methanol concentration of 10 % v/v. CO and CO 2 were monitored as side products of the overall reaction. It has been stated that CO evolution is significant at lower temperatures. As temperature increases, CO evolution is hindered and H 2 appeared boosted. We have demonstrated that other reactions such water-gas-shift or formate dehydration would participate in the overall process. On this basis, optimal operational condition for H 2 production is attained for thermo-photocatalytic reforming of methanol solution 10 % v/v at 200°C.

A bimetallic CuPd/TiO2 system has been prepared by a two‐step synthesis and was used for a methanol steam photoreforming reaction. By sequential deposition, palladium is deposited over copper nanoclusters through a galvanic replacement process. Hydrogen production by steam reforming from methanol was achieved by both thermo‐photocatalytic and photocatalytic processes. It appears that H2 production on the bimetallic system is notably higher than the Pd monometallic reference. Moreover this difference in the catalytic performance could be related to the higher CO evolution observed for the monometallic Pd1.0 TiO2 system which is partially inhibited in the bimetallic catalyst. In addition, an important thermal effect can be envisaged in all cases. Nevertheless, this improved effect in the thermo‐photocatalytic process is accompanied by a remarkable CO evolution and SMSI effect (important strong metal‐support interactions) that hindered the efficiency as temperature increases. On this basis, optimal operational conditions for H2 production are obtained for thermo‐photocatalytic reforming at 100 °C, for which the synergetic effect is higher with lower CO production (H2/CO=4).

Different Cu@Pd–TiO2 systems have been prepared by a two-step synthesis to obtain a bimetallic co-catalyst for the H2 photoreforming reaction. We find that the tailored deposition of Pd covering the Cu nanoclusters by a galvanic replacement process results in the formation of a core@shell structure. The photocatalytic H2 production after 18 h is 350 mmol/g on the Cu@Pd1.0–TiO2 bimetallic system, which is higher than that on the monometallic ones with a H2 production of 250 mmol/g on Pd-supported TiO2. Surface characterization by high-angle annular dark-field scanning transmission electron microscopy, H2-temperature-programed reduction, CO-FTIR spectroscopy, and XPS gives clear evidence of the formation of a core@shell structure. With a Pd loading of 0.2–0.3 at. %, we propose a full coverage of the Cu nanoparticles with Pd. Long-time photoreforming runs show the enhanced performance of supported Cu@Pd with respect to bare palladium leading to a more stable catalyst and ultimately higher H2 production.

A series of Ni‐Ce catalysts supported on SBA‐15 has been prepared by co‐impregnation, extensively characterized and evaluated in the carbon dioxide reforming of methane (DRM). The characterization by TEM, XRD and TPR has allowed us to determine the effect of metal loading on metal dispersion. Cerium was found to improve nickel location inside the mesopores of SBA‐15 and to suppress coke formation during the DRM reaction. The analysis by XPS allowed us to associate the high cerium dispersion with the presence of low‐coordinated Ce3+ sites, being main responsible for its promotional effect. A combination of XAS and XPS has permitted us to determine the physicochemical properties of metals under reduction conditions. The low nickel coordination number determined by XAS in N‐Ce doped systems after reduction suggests the generation of very small nickel particles which showed greater catalytic activity and stability in the reaction, and a remarkable resistance to coke formation.