A study by in-situ thermo-Raman spectroscopy was carried out to understand the structural changes occurring during the reduction of R-NiMoO 4 in different atmospheres (viz., H 2 , CO, and C 3 H 6 ) at different temperatures and time. In addition, the dynamics of R-NiMoO 4 during reduction/reoxidation were also investigated. The products from reoxidation of reduced R-NiMoO 4 in different atmospheres were analyzed by XRD. During the reaction of H 2 with R-NiMoO 4 at 400 °C a new band was detected at 455 cm -1 , which is characteristic of reduced surface molybdenum oxide species. Thus, the formation NiMoO 3 and/or Ni 2 Mo 3 O 8 suboxide intermediates was suggested. On the other hand, reversible H 2 reduction/O 2 reoxidation dynamics was observed, where the main Raman features of H 2 -reduced R-NiMoO 4 were restored completely after reoxidation by oxygen. On the contrary, during the reaction of C 3 H 6 with R-NiMoO 4 the formation of a stable suboxide was difficult to detect, and irreversible C 3 H 6 reduction/O 2 reoxidation dynamics was suggested as the extensive heating of the C 3 H 6 -reduced sample in 10% O 2 /He for 2 h at 400 °C did not restore the Raman features of the R-NiMoO 4 observed prior to reduction. No significant change was observed in the Raman spectra of R-NiMoO 4 during heating in a flow of 10% CO/He, except for the steady decrease in the intensities of all bands with increasing temperature. This may be due to the fact that at high temperatures CO decomposed and the produced carbon deposited on the sample surface.

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The hydrogen production by the catalytic partial oxidation of methanol (POM) 6 over rare earth oxide (RE = La, Dy, Gd and Ce)-modified ZnO-supported silver catalysts, as well 7 as silver supported on Ce 1-X Gd X O y -modified ZnO catalysts, was investigated. The effect of the 8 temperature on the activity was studied in the range between 150°C and 400°C, and the catalyst 9 stability was monitored with time-on-stream (TOS). The addition of rare earth metal oxide 10 promoters resulted in a significant improvement in the catalytic performance. The optimal 11 performance in methanol oxidation was achieved using AgCe20Zn, which exhibited a hydrogen 12 selectivity of 90.8% with 95.2% methanol conversion at 350°C; however, the catalyst suffered 13 from marked deactivation with TOS. The good stability of the Ag/ZnO catalyst was verified 14 using a gadolinium promoter. Doping of the AgCe20Zn catalyst by Gd greatly enhanced its life 15 span over at least 24 h on-stream and markedly reduced the CO content (down to <1%). X-ray 16 diffraction analysis indicated the formation of a Ce-Gd solid solution; hence, more oxygen 17 vacancies were generated by the substitution of Ce 4+ cations with Gd 3+ . It is proposed that the 18 oxygen vacancies in the AgCeGdZn catalysts provide a method to increase the Ag-support 19 interaction and inhibit metal sintering. H 2 -temperature-programmed reduction and transmission 20 electron microscopy results confirmed that the reducibility and dispersion of the Ag particles on 21 catalyst was greatly enhanced by Gd doping, which could contribute to the good 22 long-term activity observed for the POM reaction over AgCeGdZn catalysts. 23

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