Modulating the Interfacial Energy of Ni–Bi Molten Alloys for Enhanced Methane Decomposition to Hydrogen

Abstract

Catalytic methane decomposition is a highly promising CO₂-free hydrogen production technology with carbon material generation; however, developing catalysts that can efficiently decompose methane at moderate temperatures remains challenging. In this study, we develop a series of NiMn–Bi molten alloy catalysts with various Ni:Mn ratios for catalyzing methane decomposition. The Mn-modified Ni–Bi alloy exhibits a CH₄ conversion of 15.3% at 850 °C, and the corresponding hydrogen production rate increases by 112% compared with Ni–Bi. The ternary alloy catalyst also demonstrates stability at this production rate for up to 80 h. Molecular dynamics simulations show that the introduction of Mn significantly reduces the strong interaction between the active metal Ni and the solvent metal Bi, thereby accelerating the methane dissociation rate. More importantly, among the theoretically calculated binding energy, interfacial energy, Ni–Bi interaction, and mean-square displacement, interfacial energy, a comprehensive demonstration of surface energy and atomic interactions, is proposed as a potential descriptor for predicating and estimating the catalytic performance of the molten alloy-based catalysts.