Insights into the Mechanism of Methanol Steam Reforming for Hydrogen Production over Ni-Cu-Based Catalysts

The low cost and high selectivity toward CO2 and H-2 of Ni-Cu catalysts for the methanol steam reforming (MSR) make them excellent candidates for the production of hydrogen from methanol. Moreover, bimetallic Ni-Cu alloy blocks the production of undesirable methane, CO, and coke. In this work, the full MSR mechanism on Ni-Cu surfaces was studied by density functional theory calculations, a step forward to explain their high activity and selectivity for that reaction. The MSR evolves on Ni-Cu surfaces mostly through the methanol decomposition on the catalytic surface followed by the water-gas shift (WGS) reaction, which converts the CO obtained from methanol decomposition to CO2 and additional H-2. Direct CO2 formation from methanol should be a minority route associated with the presence of combed surfaces in the catalysts. Finally and most importantly, the Ni-Cu alloy suppresses the formation of methane and coke while the high desorption barrier for CO species avoids its production. Overall, the information gathered in this work alongside the insights into the MSR reaction mechanism on these surfaces shall aid in the future design of improved Ni-Cu alloy-based catalysts for hydrogen production through methanol.