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Density Functional Theory Study of Water-Gas-Shift Reaction on 3Cu/α-Al<sub>2</sub>O<sub>3</sub>(0001) Surface
The
water-gas-shift reaction (CO + H<sub>2</sub>O → CO<sub>2</sub> + H<sub>2</sub>) 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-Al<sub>2</sub>O<sub>3</sub>(0001) surface.
Three reaction mechanismsî—¸redox, carboxyl, and formateî—¸have
been examined. After zero-point energy correction, our calculations
show that the redox mechanism is controlled by <i>l</i>-CO<sub>2(a)</sub> formation and OH<sub>(a)</sub> diffusion. The carboxyl
mechanism is dominated by the carboxyl formation. The OH<sub>(a)</sub> is a reactive intermediate and plays an autocatalytic role in catalytic
WGS reaction. Specially, the OH<sub>(a)</sub> formation barrier can
be reduced to 0.22 eV from the water dimer dissociation, and the H<sub>2(a)</sub> formation barrier is extremely low, 0.65 eV, on the 3Cu/α-Al<sub>2</sub>O<sub>3</sub>(0001) surface