Abstract
Methanol steam reforming (MSR) is a promising technology for on-board hydrogen production in fuel cell applications. Although traditional Cu-based catalysts demonstrate high catalytic activity and selectivity towards CO2 relative to CO, which is produced via methanol decomposition, they suffer from poor thermal stability and rapid coke formation. Nickel phosphides have been widely investigated in recent years for many different catalytic reactions owing to their remarkable activity and selectivity, as well as their low cost. In this work, we present a mechanistic study of methanol decomposition and MSR pathways on Ni2P using density functional theory (DFT) calculations. DFT-predicted enthalpic barriers indicate that MSR may compete with methanol decomposition on Ni2P, in contrast to other transition metals (e.g., Pt, Pd, and Co) which primarily decompose methanol into CO. The formaldehyde intermediate (CH2O*) can react with co-adsorbed hydroxyl (OH*) from water dissociation to produce H2COOH* which then undergoes subsequent dehydrogenation steps to produce CO2 via H2COOH*-> HCOOH* -> HCOO* -> CO2. We also examined the conversion of CO into CO2 via the water-gas shift (WGS) reaction, but we ruled out this pathway because it exhibits high activation barriers on Ni2P. These findings suggest that Ni2P is a promising new catalyst for MSR.