Stability Of Ni-based Catalysts Research Articles

Efficient photothermochemical dry reforming of methane over Ni supported on ZrO2 with CeO2 incorporation

Solar-driven photothermochemical dry reforming of methane (PTC-DRM) has attracted increasing attention to address global climate issues yet still faces challenges of poor stability, especially for Ni-based catalysts. Herein, we developed a strategy to improve PTC-DRM activity and stability of Ni-based catalysts by supporting Ni nanoparticles on CeO2 incorporated ZrO2. At 700 °C under 30 suns light irradiation, the resulting Ni-CeO2/ZrO2 exhibited elevated and stable PTC-DRM with H2 and CO production rates of 713 and 693 mmol g−1 h−1 during a continuous 48 h test, respectively, much higher than those of Ce-free Ni/ZrO2 (542 mmol g−1 h−1 for H2 and 534 mmol g−1 h−1 for CO in a 24 h test). The comparisons between photothermochemical and thermochemical performance at the same temperatures indicate that introducing a small amount of CeO2 lowers the activation energies of CH4 and CO2 conversions from 68.6 and 62.9 kJ mol−1 in the dark to 54.7 and 57.7 kJ mol−1 under light, respectively. Mechanism investigation was performed through in situ DRIFTS and catalysts characterization before and after the PTC-DRM reaction, revealing that the plasmonic effect from Ni mitigates coke deposition and benefits the DRM activities and stability under light illumination. CeO2, serving as a promoter, enhances metal-support interaction, which also plays beneficial effects in continuously generating oxygen vacancies, facilitating the dissociation of carbonate intermediates, and mitigating coke deposition under light irradiation, thus boosting PTC-DRM activity and stability. This study is essential for designing cost-effective Ni-based catalysts and reaction systems for greenhouse gases conversion to produce syngas using sustainable solar energy.

Dry-reforming of methane over bimetallic Ni–M/La2O3 (M = Co, Fe): The effect of the rate of La2O2CO3 formation and phase stability on the catalytic activity and stability

Previous reports, albeit being partially contradictory, have indicated that the alloying of Ni with inexpensive transition metals, e.g. Co or Fe can affect the activity and stability of Ni-based catalysts under dry reforming conditions. In this work we critically assess the catalytic performance of Ni-based bi-metallic catalysts derived via the reduction of perovskite precursors, i.e. LaNi0.8M0.2O3 (M=Ni, Co and Fe). In-situ XRD and energy dispersive X-ray spectroscopy techniques were employed to probe metal–metal and metal–support interactions and phase transformations under reactive conditions. Ni–Co was found to be the most active catalyst, whereas Ni–Fe showed no activity. We observed that the addition of Co increases the rate of La2O2CO3 formation, which in turn enhances the removal of carbonaceous deposits from neighbouring active sites, thus, leading to a catalyst with an increased stability and activity. The poor activity of Ni–Fe was explained by the encapsulation of active Ni particle by LaFeO3.

Effect of metal oxides on the reforming of methane with carbon dioxide

The effect of basic and rare earth metal oxides on the stability of nickel-based catalysts for the CO2 reforming of CH4 has been studied. The addition of metal oxides increased the stability of Ni-based catalysts and reversed the values of the reaction orders with respect to both CH4 and CO2. In the presence of metal oxides, the values of the reaction orders with respect to CO2 partial pressure followed the same trend of catalyst stability.