A Theoretical Study of the Water-Gas-Shift Reaction on Cu6TM (TM = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au) Clusters

We perform density-functional theory calculations to investigate the water-gas-shift (WGS) reaction on Cu6TM (TM = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au) clusters through redox, carboxyl, and formate mechanisms, which correspond to CO* + O* -> CO2 (g), CO* + OH* -> COOH* -> CO2 (g) + H*, CO* + H* + O* -> CHO* + O* -> HCOO** -> CO2(g) + H* respectively. An energetic span model is used to estimate the efficiency of the three mechanisms of different Cu6TM. It finds that for groups 9 and 10, carboxyl mechanism is the predominant mechanism in the three. While for Cu6TM (Cu, Ag, Au), it finds that the formate mechanism form the TDI and TDTS. Furthermore, the turnover frequency calculations are done for every Cu6TM cluster. The results show that Cu6Co is the best catalyst for WGS reaction. Finally, to understand the high catalytic activity of the Cu6Co cluster, the nature of the interaction between adsorbate and substrate is also analyzed by the detailed electronic local density of states. These findings enrich the applications of Cu-based materials to the high activity catalytic field.