Modulating The Activity Of TM₃₈ Clusters Toward CO₂ Via Alloying Effect

The concentration of CO2 in atmosphere is increasing on an astonishing speed in the latest decades, due to the well-known greenhouse effect, which has seriously affected the mankind life. Correspondingly, people have tried many ways to reduce the concentration of CO2. Converting CO2 to other materials is potentially interesting and challenging method to utilize and reduce CO2.. In general, transition metals(TM) often possess high efficient catalysis, and their alloy clusters are expected to display different physical and chemical properties with their bulk counterparts.In this thesis, with first-principles plane wave density-functional theory calculations, we have systematically investigated the geometric and electronic structures of TM38 (Ti, Co, Cu, Ni, Rh, Pd, Ag, Pt and Au) clusters and their bimetallic alloy clusters, as well as their chemical activities towardsCO2.First, we have investigated the geometric and electronic structures of the TM38 (Ti, Co, Cu, Ni, Rh, Pd, Ag, Pt and Au) clusters and their bimetallic alloy clusters systematically, to investigate the alloying effect in modulating their geometric and electronic structures as well as their chemical activities toward CO2 molecule, with a core-shell structure model for the bimetal systems. The results show that the alloying effect can modulate their geometric structures and electronic structures, such as bond length Ro, average binding energies Eb, the magnetic properties, d-band centers Edbc. When bond length R0 becomes larger, the binding of the cluster becomes weaker, and the Edbc will be shifted closer to the Fermi levels.After we have investigated the geometric and electronic structures of the clusters, we investigated the chemical activities of TM38 clusters and their bimetallic alloy clusters toward CO2 and CO molecule adsorption. Importantly, this adsorption are also found d-band positions dependent and can be modulated by alloying with different kinds of transition metal:when the d-band centers become closer (farther) to Fermi level, their adsorption to CO2 and CO molecule become stronger (weaker). For example, when TM(Ni, Rh, Pt, Co and Pd) alloyed with the inert noble metal (Cu, Au and Ag), it is found that the d-band centers are shifted up close to the Fermi level and the adsorption energy of CO2 and CO molecules become stronger, which displays bigger adsorption energy, indicating a stronger activation, in contrast to the normal intuition that an alloy system possess the properties of the interpolation of the constitutive components.