Role of Hydrogen and Oxygen Activation over Pt and Pd-Doped Composites for Catalytic Hydrogen Combustion.

Removal of excess amount of hydrogen in a catalytic route is a safety measure to be implemented in fuel cell technologies and in nuclear power plants. Hydrogen and oxygen activation are crucial steps for hydrogen combustion that can be achieved by modifying supports with suitable noble metals. In the present study, Pt- and Pd-substituted Co3O4-ZrO2 (CZ) were synthesized using PEG-assisted sonochemical synthesis. Ionic states of Pt and Pd in CZ supports were analyzed by X-ray photoelectron spectroscopy. Pd and Pt improved H2 and O2 activation extensively, which reduced the temperature of 50% conversion (T50%) to 33 °C compared with the support (CZ). The activation energy of PdCZ catalyst was decreased by more than 2 folds (13.4 ± 1.2 kJ mol-1) compared with CZ (34.3 ± 2.3 kJ mol-1). The effect of oxygen vacancies in the reaction mechanism is found to be insignificant with Pt- and Pd-substituted CZ supports. However, oxygen vacancies play an important role when CZ alone was used as catalyst. The importance of hydrogen and oxygen activation as well as the oxygen vacancies in mechanism was studied by H2-TPD, H2-TPR, and in situ FTIR spectroscopy.