Unsupported nickel catalyst prepared from nickel foam for methane decomposition and recycling the carbon deposited spent catalyst

Catalytic methane decomposition (CMD) receives increasing attention for co-production of CO_x-free hydrogen and valuable carbon by-product, and the catalyst plays a crucial role on methane conversion and the product features. Unsupported nickel catalysts derived from commercial nickel foam (NF) were prepared for CMD by mild pre-treatment. Effects of the pre-treatment method (acid treatment, thermal treatment, acid-thermal treatment and hydrogen reduction) and reaction temperature were explored on the NF morphology and CMD reactivity in a fixed-bed reactor. It is found that catalytic performance of the NF-based catalyst is highly dependent on the pre-treatment and reaction temperature. The thermal and acid-thermal treatments could greatly promote the catalytic activity (with methane conversion up to 74.6% and 91.8%, respectively) at 850 °C. To fully release potential abilities of the catalyst, the carbon deposited spent catalyst was recycled as a fresh catalyst in the CMD test by several strategies. High and stable methane conversion (up to around 90%–93%) can be achieved by simulating the operation model in a fluidized-bed reactor for a continuous CMD process. Besides, the carbon deposited spent catalyst could serve as a promising candidate of supercapacitor electrode material.