Unveiling the Roles of Precursor Structure and Controlled Sintering on Ni-Phyllosilicate-Derived Catalysts for Low-Temperature Methane Decomposition

Abstract

Catalytic methane decomposition (CMD) is a promising technology for large-scale production of CO x -free H 2 from natural gas that can also produce valuable carbon byproducts. Although equilibrium conversions and reaction rates of CMD generally increase with temperature, operation in a low-temperature regime with simultaneous H 2 recovery could potentially lead to operating cost and energy savings. Here, we report that well-dispersed Ni–SiO 2, derived from high-temperature reduction of nickel phyllosilicates, is active for CMD at temperatures below 500 °C, with initial H 2 production rates of up to 5.3 mol H 2 /g cat ·h at 25% CH 4 conversion. This ability to achieve rates comparable to other well-established catalysts is contrary to expectations that small (<ca. 10 nm) Ni nanoparticles are inactive for CMD because of rapid deactivation and attributed here to an unusual mobility of nickel–silica interfaces in the presence of CH 4 that leads to controlled sintering of the originally well-dispersed Ni nanoparticles. We further show that the ratio of 1:1 and 2:1 nickel phyllosilicates in the precursor, which governs catalyst reducibility and can be tuned by adding NH 4 F to the synthesis mixture, is a key descriptor of catalytic performance. Our findings provide valuable insight into catalyst and process design for low-temperature CMD.