Electronic origin of catalytic methane pyrolysis on NiMoM-Bi alloys: a bader charge descriptor

Abstract

Methane pyrolysis can produce hydrogen without direct CO 2 emissions, but catalyst deactivation by solid carbon remains a central barrier. Molten alloys provide dynamically renewed catalytic interfaces, but promoter effects on methane activation remain poorly resolved. Here we examine whether a fourth transition-metal element can tune methane activation in NiMo-Bi molten alloys. Density functional theory calculations show that NiMoM-Bi alloys (M = 3d–5d transition metals) have negative formation and cohesive energies, indicating favorable thermodynamic stability. Introducing M reshapes the local Ni-Bi environment and changes the disorder of the Bi-rich alloy. Among the screened elements, Pt, Au, Re and Ir show the shortest observed times for the first CH 4 -to-CH 3 dehydrogenation step. Bader charge analysis shows that a more positive Ni charge is associated with shorter first C–H cleavage times (R 2 = 0.8505), supporting its use as a correlational screening descriptor. These results connect methane activation in NiMoM-Bi molten alloys to local electronic structure and provide a descriptor for screening methane-pyrolysis catalysts. This study identifies candidate compositions and testable hypotheses for subsequent experimental assessment of methane-pyrolysis catalysts.