Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Cong Liu Project Name: Hetero_Catalysis Division: MSD Project title: Development and Application of Accurate Theoretical Models for Calculating the Thermodynamics of Chemical Bonds for Heterogeneous Catalysis Associated funding: Postdoctoral Director’s Fellowship at Argonne Other Systems: Science: The conversion of CO2 to fuels is of use for renewables in carbon-neutral technologies and for developing approaches to mitigate global warming. The high thermodynamic stability of the CO2 molecule requires substantial input of energy for its reduction and conversion. Although a number of recent studies have helped to better understand CO2 activation/reduction using catalysts, the catalytic conversion of CO2 to hydrocarbon fuels (e.g., CH3OH, CH4) is still a challenging problem. For instance, although CO2 has been shown to be reduced directly on metal surfaces, the surfaces become quickly poisoned and deactivated by the reduction products (e.g., CO).[1] Studies have achieved the reduction of CO2 to CO and formate. However, further transformation of CO and formate to more useful products such as methane or methanol requires multiple hydrogenation steps, and has only been demonstrated with low efficiency. Our work in this area will be focused on using computational methods to understand the chemical insights of the reductive conversion of CO2 to hydrocarbons on supported transition metal clusters. Recently, size-selected subnanometer transition metal clusters have gained great attention in catalysis, due to their unique electronic and catalytic properties, which deviate from extended metal surfaces and larger nanoparticles. Typically, for very small clusters (diameters below around 2 nm), quantum effects become noticeable, referred to as the “catalytic finite-size effect”.[1] Vajda et al. have successfully synthesized subnanometer metal and metal oxide clusters with very narrow size distributions on thin film support materials (e.g. alumina). These materials have shown great potential in catalytic reactions. For instance, the electrocatalysis of water oxidation was studied using Pd4, Pd6 and Pd17 clusters on an ultrananocrystalline diamond Si-coated electrode,[2] indicatin g that these clusters have stable electrochemical potentials over several cycles. Also, in a study of epoxidation of propylene using Ag3 clusters,[3] they discovered that Ag3 clusters are highly reactive in the dissociation of O2; the calculated O-O cleavage barrier is less than a half eV. In our recent computational study of the electrochemical reduction of CO2 to CH4,[4] Co4 was found to provide high reactivity with an overpotential of less than 1 V. We will be closely collaborating with Stefan Vajda’s research group at Argonne National Laboratory. Vajda’s group, especially, has extended experience and technology on controlling the particle size of metal clusters/nanoparticles, and has had successful collaborations with our group on the studies of metal cluster mediated water oxidation[2] and other catatalytic reactions.[2-4] Recently, we published a study on CO2 hydrogenation to CH3OH on alumina supported Cu4 clusters. [5] Our results showed that Cu4 is the most activ e low-pressure catalyst for methanol synthesis from CO2 hydrogenation.[5] In this study, our calculations (using the CNM Carbon cluster) on the reaction mechanism of CO2 reduction on Cu4 predicted the high activity of Cu4 prior to experiment. These promising results lead us to the future investigations on cluster size effect and different support materials (e.g., carbon nanotubes (CNTs), graphene, iron oxide), as well as the CO2 conversion to other hydrocarbons (e.g., CH4, C2H4). Therefore, a comprehensive theoretical investigation will play an important role and will be closely coupled with experimental work. Project description: Previously, we have studied CO2 reduction to CH3OH on alumina supported Cu4 clusters.[6] In the following year we will systematic studies of CO2 conversion to hydrocarbons using other Cu clusters (e.g., Cu3 and Cu20) supported on CNTs, graphene and aluminum oxide. The electronic and catalytic properties of the nanomaterials, metal-dependence, possible intermediates and transition states of the catalysis will be studied. These studies will provide crucial information for molecular insight into chemical reduction of CO2 and result in significant advancements in the development of novel efficient nanocatalysts. The following calculations will be performed: a. Gas-phase Cu3 and Cu20 clusters will be studied and compared to Cu4 cluster primarily to investigate the reaction mechanisms of CO2 reduction to C1-C2 hydrocarbons, as well as the size effects of the clusters. All possible reaction pathways will be calculated using DFT methods using the VASP package. All the intermediates, transition states and products will be explored. The proposed reaction paths will then be analyzed and compared from the thermodynamic point of view. The most likely reaction mechanism will be identified based on our calculations and the experimental observations. The electronic and energetic effects of the cluster size will be studied. These calculations are difficult, because the conformations of many of these metal clusters are unknown and first have to be identified using accurate DFT methods. These calculations will be carried out within both VASP and Gaussian09 packages. b. The catalytic properties of materials supported metal clusters will also be explored. CNTs, graphene and aluminum oxide will be considered as support materials. Interactions between the support materials and metal clusters and the effect of defects on CNTs and graphene will be calculated using DFT methods within VASP package. The simulation of defects on CNTs will begin with a two-dimensional graphene model, with replacements of carbon atoms by N and O. The partial charges of surrounding carbon atoms will be determined as a parameter to measure the charge transfer interactions. Then the interaction between the Cu clusters and CNTs will be studied. The interaction between the Cu clusters and aluminum oxide surfaces (hydroxylated) will be focused on the electron transfer interaction and the effect of the hydroxyl groups on the surface. c. Finally, based on the results in parts b and c, the best Cu catalyst will be identified for catalytic CO2 reduction. This will help the experimentalists better understand the details of the catalytic reaction and the role of the catalyst. Furthermore, insights to the effects of cluster size and support materials will be provided to guide experimental study by our collaborators. Based on this reaction mechanism, future computational studies will be carried out on different metal clusters (e.g., Co and Pt clusters) and metal alloy clusters. An assessment of the necessary calculations indicates that at least 400,000 core hours are necessary to complete this work. Industry partnership: Project URL: Current FY Hours Used: undetermined amount New FY Requested allocation: 400000 Q1: 100000 Q2: 100000 Q3: 100000 Q4: 100000 Justification: Storage requirements: Thank You, The LCRC Accounts System