Density Functional Theory Study of Water-Gas-Shift Reaction on 3Cu/α-Al₂O₃(0001) Surface

The water-gas-shift reaction (CO + H₂O → CO₂ + H₂) plays a key role in hydrogen economy. First-principles density functional theory has been used to investigate the mechanism of the water-gas-shift reaction on a model consisting of 3Cu atom cluster on an 3Cu/α-Al₂O₃(0001) surface. Three reaction mechanismsredox, carboxyl, and formatehave been examined. After zero-point energy correction, our calculations show that the redox mechanism is controlled by l-CO_2(a) formation and OH_(a) diffusion. The carboxyl mechanism is dominated by the carboxyl formation. The OH_(a) is a reactive intermediate and plays an autocatalytic role in catalytic WGS reaction. Specially, the OH_(a) formation barrier can be reduced to 0.22 eV from the water dimer dissociation, and the H_2(a) formation barrier is extremely low, 0.65 eV, on the 3Cu/α-Al₂O₃(0001) surface.