Methane Activation and Coupling Pathways on Ni[sub.2]P Catalyst

The direct catalytic conversion of methane (CH[sub.4]) to higher hydrocarbons has attracted considerable attention in recent years because of the increasing supply of natural gas. Efficient and selective catalytic conversion of methane to value-added products, however, remains a major challenge. Recent studies have shown that the incorporation of phosphorus atoms in transition metals improves their selectivity and resistance to coke formation for many catalytic reactions. In this work, we report a density function theory-based investigation of methane activation and C[sub.2] product formation on Ni[sub.2]P(001). Our results indicate that, despite the lower reactivity of Ni[sub.2]P relative to Ni, the addition of phosphorus atoms hinders excessive dehydrogenation of methane to CH* and C* species, thus reducing carbon deposition on the surface. CH[sub.3]* and CH[sub.2]* moieties, instead, are more likely to be the most abundant surface intermediates once the initial C-H bond in methane is activated with a barrier of 246 kJ mol[sup.−1]. The formation of ethylene from 2CH[sub.2]* on Ni[sub.2]P is facile with a barrier of 56 kJ mol[sup.−1], which is consistent with prior experimental studies. Collectively, these findings suggest that Ni[sub.2]P may be an attractive catalyst for selective methane conversion to ethylene.