Selenium-promoted methane pyrolysis over molten Ni-Bi alloys: interfacial restructuring and electronic regulation

Methane pyrolysis offers a CO_X-free route for hydrogen production. Molten alloy catalysts are promising due to their liquid interface and resistance to carbon deactivation, but the atomic-scale promotion mechanism of dopants remains unclear. Here, density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations were used to study Se promotion in molten Ni-Bi alloys (Ni₂₇Bi₇₃vs. Ni₂₇Bi₇₂Se₁). Results show that Se maintains the Bi-rich surface and forms local Ni-Se coordination in the near-surface region, dispersing interfacial Ni sites. Se withdraws electron density from Ni and downshifts the Ni d-band center from -1.194 to -1.332 eV, weakening intermediate adsorption. The free-energy barrier for the first C-H cleavage is reduced from 3.28 to 2.79 eV, and AIMD confirms faster subsequent dehydrogenation. This work clarifies Se-induced interfacial and electronic regulation, providing a theoretical basis for designing high-performance molten catalysts for methane pyrolysis.