NiC_x/Ni-foam discovered as a promising high-temperature WGSR catalyst

Water gas shift reaction (WGSR) is urgently calling for an alternative to the Fe-Cr catalyst. Ni-based catalysts are taken into consideration but remain challenging because of their high methanation activity. Here we report a highly active and selective NiC_x/Ni-foam catalyst with clearly detectable Ni₃C phase, facilely obtainable by endogenous growth of NiC₂O₄ onto a Ni-foam and subsequent H₂-reduction treatment. The preferred catalyst with high content of NiC_x is capable of converting 63.6% or 94.3% CO at 350 °C or 400 °C with trace or < 0.8% CH₄ formation for a feed gas with H₂O/CO/Ar molar ratio of 4/1/9, and is stable for at least 110 h. It is experimentally and theoretically unveiled that the Ni₃C facilitates the dissociative activation of H₂O and favors CO to form carboxylate species (favorable for CO₂ formation) rather than active Ni(CO)_n intermediates for CH₄ formation thereby enabling the catalyst with high WGSR activity and selectivity.