Unveiling the Roles of Precursor Structure and Controlled Sintering on Ni-Phyllosilicate-Derived Catalysts for Low-Temperature Methane Decomposition
Emmerson Hondo, Terry Z. H. Gani, Mohammadreza Kosari, Shibo Xi, Bella Bella, Jangam Ashok, Ji Yang Tan, Tianchang Wang, Hui Bian, Kang Hui Lim, Luwei Chen, Jie Chang, Armando Borgna, Sibudjing Kawi
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.