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By means of periodic density functional theory calculations, we have investigated the structure, bonding, and catalytic property of defect graphene decorated Pd–Ni nanoparticles. According to systematical structure calculations for Pd–Ni nanoparticle, we found that Pd atoms tend to occupy the positions with lower coordination number and Ni atoms prefer to locate at the position with high coordination number resulting in the formation of core–shell Ni–Pd nanoparticles which agrees with the experimental observation. The lowest-energy Pd6Ni4and Pd4Ni6isomers are selected to examine the interaction between Pd–Ni nanoparticle and defect graphene. The adsorption energies are calculated to be −5.26 and −4.22 eV/atom for the Pd6Ni4and Pd4Ni6on the defect graphene, respectively. In addition, we found that more Ni–C bonding formation in the interface region could enhance the interaction between Pd–Ni nanoparticle and the defect graphene. Through the analysis of the electronic structures of Pd6Ni4and Pd4Ni6on the defect graphene, it is found that by using Ni atoms to combine with the defect site could prevent the electron missing from Pd atoms directly benefit the cluster dispersion without sacrificing the overall catalytic performance. The resulting Pd–Ni/defect graphene catalyst exhibits high activity and selectivity for the formation of formic acid from CO2and H2.

The microscopic reaction mechanisms for the water adsorption/dissociation and hydrogen generation processes on the α-Al2O3(0001) surface are clarified by using spin-polarized density functional theory with the projected augmented wave approach. The adsorptions of OH, O, and H species are also examined. Calculations show that the H2O, OH, O, and H species prefer to adsorb at the Al(II)-top, Al(I, II)-top, Al(I, II)-bridge, and Al(II)-top sites with adsorption energies of −1.34, −5.91, −8.22, and −3.14 eV on the Al-terminated surface, whereas those are Al-top, Al-top, Al-top, and O-top sites with adsorption energies of −1.11, −2.79, −2.00, and −2.23 eV for the Al, O-terminated surface. Geometries of the molecular adsorbed intermediates, transition states, and the hydroxylated products as well as the energetic reaction routes are fully elucidated. Hydrogen generation and full dissociation of water are found to occur on the Al-terminated surface with overall exothermicities of 2.37 and 4.22 eV, whereas only the production of coadsorbed H(ads)+ OH(ads)is observed on the Al, O-terminated surface with an overall exothermicity of 1.06–1.64 eV. In addition, the local density of states and Bader charge calculations are carried out to study the interaction between the adsorbate and surface along the reaction.

We applied periodic density-functional theory to investigate the interaction of a Pt13cluster on graphene oxide (GO) sheets at varied ratios of oxygen to carbon and on a pristine graphene sheet. Relative to a pristine graphene sheet, the existence of oxygen atoms in an appropriate proportion in the formation of graphene oxide enhanced the adsorption capability of a Pt13cluster. The O/C ratio of GO sheets had the following influences on the Pt13cluster adsorption behavior: (i) for O/C ratio < 0.125, the Pt13cluster abstracted the neighboring oxygen atom from a GO sheet to form Pt13O, or aggregated with an adjacent cluster to form a larger cluster; (ii) for O/C ratio ≥ 0.125, the Pt13cluster was stabilized and dispersed on the GO sheet. We calculated also the adsorption behavior of carbon monoxide on a Pt13/GO sheet; a strong interaction between the Pt13cluster and the GO sheet modulated the electronic structure of the Pt13cluster, thus decreasing the CO adsorption energy, which in turn decreased the combined barriers, CO + O and CO + OH, in the water-gas shift reaction (WGSR) and improved the CO tolerance of the Pt catalyst.

We applied periodic density functional theory to investigate the adsorption of CO2on WC(0001) and various WC-Co alloy surfaces and discuss the reaction trend of dissociation of CO2and hydrogenation on these surfaces. We employed an electron localization function (ELF) to investigate the effect of electron localization or delocalization on various WC-Co alloy surfaces with a varied Co coverage; the partial-delocalization surfaces (WC-Co (0.25 ML) surface) exhibit the largest energy of adsorption of CO2(−1.61 eV) on all calculated surfaces. When we increased the Co ratio to form a WC-2Co (0.50 ML) surface, the activation energy for the dissociation CO2→CO+O decreased to 0.57 eV. The energy of CO2hydrogenation to form formate (CO2+H → HCOO) decreases with Co coverage due to increased electron delocalization.

We applied periodic density-functional theory to investigate the adsorption and dissociation of NO on bimetallic surfaces, including the xNi@Pt(111), NixPt4−x(111), and (4−x)Pt@Ni(111) surfaces (x= 0−4). For all bimetallic surfaces, NO is preferentially adsorbed on Ni-rich sites, and the adsorption energies increase with an increasing number of top-layer Ni atoms on the surface. When the top-layer compositions are equal (but with varied composition of inner layers), the adsorption energy of NO on these surfaces decreases in the order xNi@Pt(111) > NixPt4−x(111) > (4−x)Pt@Ni(111), whereas the NO dissociation barriers increase in the opposite order; a larger adsorption energy of NO leads to a smaller NO dissociation barrier. We employed the local density of states to investigate the inner-layer effect of the various surfaces; the inner-layer Pt atoms of the 4Ni@Pt(111) surface caused the greatest upshift of the d-band center (of top-layer Ni atoms) toward the Fermi energy, so that the 4Ni@Pt(111) surface exhibited the greatest NO adsorption energy, −2.97 eV, and the smallest NO dissociation barrier, 1.20 eV. In contrast, the inner-layer Ni atoms of the (4−x)Pt@Ni(111) surfaces cause a downshift of the d-band center from the Fermi energy and show much smaller NO adsorption energies and larger NO dissociation barriers. The order of reactivity for dissociation of NO (4Ni@Pt(111) > Ni(111) > NixPt4−x(111) > Pt(111) > 4Pt@Ni(111)) indicates that various combinations of Ni and Pt would produce varied catalytic effects.

We applied periodic density-functional theory to investigate the dehydrogenation of ethanol with and without H2O molecules on a 2Rh/γ-Al2O3(110) surface. In the absence of H2O, the adsorption energy of ethanol on the surface was calculated to be −31.34 kcal/mol; ethanol might form a four- or five-membered-ring (oxametallacyclic) structure on the surface. Both rings are stable but can be dehydrogenated to form aldehyde and ethene, or the C−C bond can break to form CH3(a)+ CO(a)with a dissociation barrier of 24.92 kcal/mol, eventually. When water molecules (3H2O) are present on the surface, the adsorption energy of ethanol is decreased to −21.25 kcal/mol; ethanol can neither form a ring structure on the surface nor create a path to produce aldehyde or ethene, but instead undertakes uniquely the scission of the C−C bond, forming CH3(a)+ CO(a)with a barrier of 21.55 kcal/mol.