Ultrafine PdOx nanoparticles on spinel oxides by galvanic displacement for catalytic combustion of methane
High light-off temperature and poor water-tolerance at low temperature are the mains drawbacks of catalysts for catalytic methane combustion. Herein, the galvanic displacement method was adopted to obtain ultrafine PdOx nanoparticles (~1 nm) on NiCo2O4 and build up a tight Pd-NiCo2O4 interface. As comparison, additional reference samples were prepared by conventional synthetic methods. The synthesized catalysts were characterized by XRD, TEM, XPS, H2-TPR, CH4-TPR, CO2-TPD and in situ DRIFT techniques. It is found that the obtained catalyst by galvanic displacement has more Pd4+ and more oxygen vacancies. The high oxidation state of Pd is more conducive to the activation of methane, and a large number of oxygen vacancies can promote the dissociation of C-H bond in methane. Thus, this catalyst displays outstanding catalytic activity with T90 = 260 °C and excellent water-tolerance below 300 °C. In addition, a simple model was based on obtained results to understand catalytic mechanism and give a universal strategy for rational designing catalyst for low temperature complete oxidation of methane in the future.