Electronic Properties, Adsorption And ORR Of Metal Clusters

At present, there are some challenges in the process of industrialization andcommercialization for fuel cell. One of these problems is the use of Pt-based catalysts in fuelcell for industrialization and commercialization. It is well-know noble metal Pt is a rare metal,and its prize is expensive, which limits large-scale use. the used Pt-catalyst in fuel cells causesthe high cost of fuel cells. Meanwhile, reducing CO poisoning of anode catalyst is anotherproblem, and seeking suitable storage H materials is also an important task. Based on theseissues to be resolved, we try to seek some new catalysts, which have some properties,including low rate of CO poisoning of the catalyst performance, and higher economiceffectiveness.First, we introduced the background and status of research and research topics, includingproton exchange membrane fuel cells (PEMFC), oxygen reduction reaction (ORR) on metalsurface, bimetallic nano-catalysts, design principles of alloy catalysts, and the transition statetheory. Molecular orbital theory and density functional theory (DFT), whose were involved inthe section.Secondly, the electronic properties of metal clusters have been exploring the properties atatom level, especially bimetallic AgCu clusters, and the electronic properties of binaryclusters is different from the pure clusters. Bimetallic AgCu also shows catalytic properties.Then, the CO oxidation process on Ag-doped Au clusters and Cu-doped Ag clusters wasexplored at the atomic level, which reveals the shell-core nanoparticles could improve the COoxidation. In contrast to the oxidation of CO molecules on pure Ag13, Au13clusters, shell-coreclusters enhance the anti-bonding effect of O2molecules in CO oxidation process. DOSanalysis shows d-band center energy level of shell-core clusters has increased, which providea more effective catalyst for bimetallic cluster AgCu and AuAg. Comparing with COoxidation at different charge of AgCu or AgAu clusters, CO oxidation on catalysts with (-1)charge state shows a better performance. DOS show that d-band center level at (-1) chargestate is near Fermi lever, which indicates that the bimetallic clusters is helpful for COoxidation. Under CO+O2co-adsorbed on Ag12Cu or Ag13, CO oxidation process showCu-doping in Ag clusters deceases most reaction barrier CO oxidation. Subsequently, we studied O2molecules adsorbed and dissociation on bimetallic AgCu surface,and explored how the different proportions of AgCu ingredients affect the catalyticperformance. We found O2adsorption is enhanced with the increase in adsorption sites of Cuatoms, while the dissociation can significantly reduce. Adsorption sites containing2Ag+Cuatoms are suitable for adsorption and dissociation energy barrier. We predicted the site of2Ag+Cu is a good active site for ORR. O2molecules for adsorption on the graphite-supportedPtNi clusters have been discussed and analyzed. O2adsorption on supported PtNi clusters isdifferent from one on bare PtNi clusters. DOS analysis shows less change in electricalcharacteristics of graphite-supported Pt3Ni. It is possible for us to understand that Pt3Ni classclusters on the graphite support remain efficient catalysis in the atomic electrons level. ORRprocess on adsorption sites with2Ag+Cu was calculated, and reversal potential and possibleadsorption of intermediate states indecated ORR process on adsorption sites with2Ag+Cu istoward four electronic process. The d-band center analysis showed that the electronic propertyof adsorption sites with2Ag+Cu is helpful for ORR. Catalytic porperties of AgCu indicatedthe proper composition and structure can achieve an effective reduction of oxygen, andreduction of H2O2on AgCu bimetallic dendrites showed a good catalytic properties of AgCubimetallic material.Al-, Ca-, Mn-doping in MgNi clusters lengthen d(Mg-Ni), increase also Mulliken charge andatomic magnetic moment on most shell atoms. These are helpful for understanding hydrogenstorage. Compairion with bulk MgNi alloy, reaction heats of hydrogenation, enthalpies offormation, desorption energies show Mg8Ni4M(M=Ni, Al, Ca, Mn) clusters have a property ofhydrogen storage materials with relatively higher reaction heat of hydrogenation, and theirhydrides have a lower desorption energy.