A closed-loop framework for descriptor-empowered exploration of high-activity Co-based quaternary molten alloy catalysts for methane pyrolysis.

Methane (CH4) pyrolysis via molten media offers an attractive route to CO2-free hydrogen production with high-value carbon as a co-product. However, the rational design of multicomponent molten catalysts remains challenging due to the dynamic and disordered nature of active sites in the molten state. Here, we present a closed-loop framework that integrates potential catalyst exploration by descriptor data mining, CH4 pyrolysis testing, and activity mechanism analysis to identify high-activity catalysts for CH4 pyrolysis. Using this approach, Bi70Ni18Cu6Co6 is identified as a promising catalyst, with experimental validation demonstrating that it can achieve 40.3% CH4 conversion at a moderate 1000 °C with a relatively low activation energy (197.3 kJ mol-1), outperforming Bi73Ni27 (33.3%) and Bi76Ni18Cu6 (37.4%) molten media under the same experimental conditions. The enhancement stems from a synergistic multi-solute effect, whereby the co-dissolution of Ni, Cu, and Co in the low-surface-tension Bi solvent increases the density of exposed active sites and promotes direct interaction with CH4 molecules. In particular, introducing Co downshifts the LUMO energy level of the CH4 molecular orbital (∼1.3 eV), facilitating charge antibonding occupation, weakening C-H bonds, and thereby accelerating CH4 dissociation. These findings provide deep insights into Co-based multi-elementary molten catalysts and chart a clear path toward the rational design of high-performance multicomponent molten catalysts for CH4 pyrolysis.