Aerosol-phase synthesis of bimetallic NiCu oxide-decorated CeO2 nanoparticle cluster for catalytic methane combustion

Abstract

• Successful aerosol synthesis of NiCuOx@CeO2 for catalytic methane combustion. • Composition and crystalline of the hybrid nanostructure were tunable. • Superior catalytic activity (TOFCH4: 0.483 s −1 at 400 °C) was achievable. • Ni-preferred adsorption and dissociation of methane was rate-determining step. A raspberry-structured hybrid nanocatalyst composed of spherical NiCu bimetallic oxide nanoparticle decorated on ceria nanoparticle cluster (NiCuO x @CeO 2 ) was successfully synthesized via a gas-phase evaporation-induced self-assembly approach. Chemical composition and crystalline of the NiCuO x @CeO 2 were tunable during the gas-phase synthesis. The NiCuO x @CeO 2 demonstrates superior catalytic performance toward methane combustion, showing low light-off temperature (∼350 °C), high conversion ratio, high turnover frequency (0.483 s −1 at 400 °C) and sufficiently high 8-h operation stability were achievable by adjusting the composition of the catalysts. The results show that 1Ni0CuO x @CeO 2 (i.e., the sample without CuO) demonstrated the highest catalytic activity, implying adsorption and dissociation of CH 4 (i.e., preferably on NiO) was rate-determining step. Significant higher activity, especially under a low temperature range (<380 °C), was identified for the hybrid NiCuO x @CeO 2 samples under an oxygen-lean condition than in oxygen-rich condition, indicating the addition of CuO promoted redox ability of NiCuO x in the hybrid nanostructure. The stability was shown to be proportional to the ratio of NiO in the catalysts, indicating that increase of NiO amount was beneficial for thermal stability. The prototype study demonstrates the development of bimetallic-based hybrid nanostructured catalysts nanoparticle clusters. The mechanistic understanding developed in this study shows promise for the tuning of the abilities in methane dissociation versus its redox properties to achieve an optimal performance in methane-based energy applications.