Abundant hydrogen production over well dispersed nickel nanoparticles confined in mesoporous metal oxides in partial oxidation of methane

To improve the stability of Ni catalysts and employ reactive oxygen species in reducible metal oxides, the Ni nanoparticles were confined within mesoporous metal oxides (La₂O₃, Yb₂O₃, ZrO₂, CeO₂) via evaporation-induced self assembly technique utilizing 3D honeycomb-like silica as substrate for partial oxidation of methane (POM). Compared with supported catalysts, the prepared catalysts showed superior catalysts stability especially 3D honeycomb-like ZrO₂ and CeO₂ supported Ni catalysts (Ni/3HL-ZrO₂-SiO₂ and Ni/3HL-CeO₂-SiO₂) due to confinement effect and strong interaction between Ni and metal oxides. CH₄ conversion reached 90%–92%. Outstanding catalytic activity was attributed to highly dispersity of active metal. More importantly, abundant hydrogen production was observed over mesoporous CeO₂, ZrO₂ supported catalysts and the ratio of H₂/CO changed from nominal value 2 to 3. DFT theoretical calculations illuminated structural defect sites of reducible support like CeO₂, ZrO₂ afforded generation of surface hydroxyl group, which can be regenerated by activation of water and reoxidation of CeO₂, ZrO₂. Hydroxyl group was beneficial to accelerate greatly water gas shift reaction, promoting the production of hydrogen. This may provide a strategy to regulate production composition of POM to expand its downstream process.