A density functional theory (DFT) calculation has been carried out to investigate a water–gas-shift reaction (WGSR) on a series of chemical related materials of Co, Ni, and Cu (from the 3d row); Rh, Pd, and Ag (from the 4d row); and Ir, Pt, and Au (from the 5d row). The result shows that WGSR mechanism involves the redox, carboxyl, and formate pathways, which correspond to CO* + O* → CO2(g), CO* + OH* → COOH* → CO2(g) + H*, and CO* + H* + O* → CHO* + O* → HCOO** → CO2(g) + H*, respectively. The reaction barriers in the three pathways are competitive and have a similar trend that groups 9 > 10 > 11 and 3d > 4d >5d. Thus, the bottom-right d-block metals (Cu, Pt, and Au) show better WGSR activity. The experimentally most observed formate can be attributed to its lower formation and higher dissociation barriers. Furthermore, the catalytic behavior on these active metal surfaces has been examined. The result shows that WGSR is mostly follows the redox pathway on Au(111) surface due to the negligible CO* oxidation barriers; on the other hand, all the three pathways contribute similarly in WGSR on Cu(111) and Pt(111) surfaces. Finally, the feasible steps of formyl in Fischer–Tropsch synthesis (FTS), the combustion reaction, and formate pathway, CHO* → CH* + O*, CHO* → CO* + H*, and CHO* + O* → HCOO**, respectively, have also been studied. The result shows that activities of FTS and the WGSR have opposite trends on these metal surfaces.

The mechanism of the water gas shift reaction (WGSR) on the close-packed transition metal surfaces of Co, Ni, Cu (from the 3d row), Rh, Pd, Ag (from the 4d row), Ir, Pt, and Au (from the 5d row) has been systematically examined by periodic density functional theory (DFT) calculations. The comparison of potential energy surface (PES) concludes that WGSR activity is influenced by two kinds of elementary steps: O−H bond dissociation and C−O bond formation. Activation barriers (Ea) and reaction energies (ΔH) on a series of metal surfaces show good BEP relationship; however, their energetic trends are opposite in these two kinds of steps. In O−H bond dissociation steps, trends of Ea and ΔH are groups 9 < 10 < 11 and 3d < 4d < 5d. On the other hand, C−O bond formation steps on the surfaces of the lower-right metals in the d block (Cu, Ag, Pt, Au) have relatively lower Ea and ΔH, which is responsible for their high WGSR activity of metal/oxide catalysts. In addition, the fundamental of energetic trends has been examined from the analyses of adsorption energy, density of state (DOS), and charge density. The result shows that the surfaces of upper-left d-block metals (Co, Ni, Rh) with higher energy and smaller delocalization of their d orbitals yield a stronger adsorption energy with higher induced charges that will stabilize dissociating fragments to lower the barrier and retard desorptions to lift the barrier in O−H bond dissociation and C−O bond formation steps, respectively. The prediction of energetic trends in the present work is also appropriate for other catalytic reactions, such as ethanol decomposition and CO oxidation, and can help us scientifically design a better catalyst for the desired reaction.