Theoretical Study of Intermetallic Compound Nanoalloys for Direct Conversion of Methane to Methanol

Abstract

The conversion of methane into methanol is of significant environmental and economic importance; however, there are still significant issues of selectivity and efficiency that need to be addressed. This study employs density functional theory (DFT) and microkinetic modeling to investigate the potential of A 3 M (A, M = Ag, Cu, and Pd; A ≠ M) intermetallic compound nanoalloys (IMCs) for the selective oxidation of methane to methanol (MTM) using nitrous oxide (N 2 O) as an oxidant. The results show that the configuration of N 2 O parallelly adsorbed on the IMC nanoalloys is more stable than that of the vertical adsorption. This configuration is also in favor of N 2 O dissociation, as deduced from charge transfer, density of states (DOS), and crystal orbital Hamilton population (COHP) analysis. Among these intermetallic compounds, Cu-based IMCs (Cu 3 Ag(111) and Cu 3 Pd( 111)) were identified as the most effective candidates for N 2 O dissociation. With subsequent dissociative adsorption of methane, two reaction mechanisms for methane oxidation to methanol on these two screened catalysts were explored, which are the −CH 3 O and −OH pathways. Microkinetic simulations revealed the potential of Cu 3 Ag and Cu 3 Pd IMCs to serve as effective catalysts for the MTM reaction under specific reactive conditions. This work offers an approach to understanding and designing IMC catalysts for the direct conversion of methane to methanol.