Low temperature hydrogen production from methane on cerium nickel- and zirconium-based oxyhydrides

Hydrogen production from methane has been obtained at low temperature, in presence of O2, over cerium nickel and zirconium CeZrzNixOy (z = 0 or 0.5 and 0 < x ≤ 3) oxyhydrides. A H2 yield of 100% is obtained at high temperature (650 °C), at 200 °C a yield of 34% is reached with a stable methane conversion at 53% and selectivity in H2 at 64% when the solid is previously in situ treated in H2 at 200 °C. Different physicochemical techniques have been used to characterize the catalysts. Depending on the composition and metal loading, a solid solution and/or a highly dispersed nickel oxide in ceria (or ceria–zirconia) can be obtained. Ion sputtering followed by XPS analysis has been very useful for estimating the size of small NiO clusters (10–15 Å) present in the compounds. Correlations among the species present in the solid, and the catalytic performances are discussed, an active site based on the formation of anionic vacancies and a mechanism involving a heterolytic abstraction of a hydride species from methane are proposed.