Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Liang Li Applicant's institution: ANL Applicant's division: NST Project Name: PhotoCu2O Project title: Density Functional Theory Study on the Reactivity of Surface-modified Cu2O Photocatalyst Associated funding: Integrated Imaging Strategic Initiative LDRD, DOE Other Systems: Internal: 500,000 core-hours, Carbon cluster at Center for Nanoscale Materials Science: The photoreduction of gaseous CO2 to liquid fuels has attracted considerable attention over the past few decades as a technically viable and environmentally responsible means to mitigate the global warming and fuel crises. However, CO2 is an extremely stable molecule and CO2 reduction is an energetically demanding process, so the design of efficient photocatalyst is shown to be of foremost importance. Cu2O is a particularly attractive candidate for the next-generation photocatalyst because of its high absorption coefficient and small electron affinity. Theoretical studies showed that Cu2O is thermodynamically capable of photocatalytic reduction of CO2 to methanol, but practically the stepwise CO2 reduction reactions are significantly hindered by kinetic reasons, and computational and experimental studies indicate that the CO2 conversion rate is quite limited on stoichiometric, defect-free oxide surfaces due to the low catalytic reactivity. However, it is shown that defected or modified surfaces typically have better catalytic performance. Herein, we propose a comprehensive computational study, performed in conjunction with experimental work by collaborators, to systematically investigate the effect of surface steps and transition metal dichalcogenides (TMDCs) coatings on the catalytic reactivity of Cu2O surfaces with different geometries. This work is directly integrated w ith experimental imaging in the sense that simulated Transmission Electron Microscopy (TEM) and Scanning Tunneling Microscopy (STM) images will be generated based on the ab-initio-deduced surface structure models and a direct comparison can thus be made with experiments. Project description: The proposed work involves Density Functional Theory (DFT) calculations of CO2 reductive reactions on pristine, stepped and coated Cu2O surfaces, with the goals of (a) identifying the active sites in the photocatalytic reactions on both flat and stepped surfaces, (b) understanding the atomistic mechanisms dominating the reaction kinetics and (c) determining the thermodynamically favorable structures of Cu2O surfaces with TMDCs coating. Different low-index Cu2O surface orientations, i.e. (100), (110) and (111), as well high-index surface facets, will be considered in our study. DFT total energy calculations and Ab-initio Molecular Dynamics (AIMD) will be employed in determining the favorable adsorption sites and configurations for CO2 and other intermediate products. It is expected that the insights derived from this work can help to advance the knowledge on elementary processes involved in CO2 reduction and to provide atomic-scale understanding towar d rational design of kinetically facile nanosystems. The proposed calculations will be performed using the plane wave DFT code Vienna Ab-initio Simulation Package(VASP). The PBE exchange-correlation functional will be used, in conjunction with the Hubbard U correction. The following calculations are specifically proposed for this study: (a) Various structural and electronic properties of bulk Cu2O will be calculated. and the convergence of CO molecule absorption energy on Cu2O(100) and (110) surface slabs will be tested by varying the slab geometry. The calculations on bulk Cu2O require 5,000 cores hours, whereas the calculations on clean and CO-adsorbed Cu2O slabs typically require 8 and 12 hours on 32 cores, respectively, and considering that there are 15 different configurations to investigate, (8+12)*32*15 ~7,600 core-hours would be a reasonable estimate. All together we request 5,000+9,600=14,600 core-hours for this part. (b) The energetics and kinetics of the CO2 reduction processes will be investigated on ten types of flat surfaces with different orientations and absorption sites, and another three types of stepped surfaces with high miller indices.On average, each calculation on flat surfaces runs 12 hours on 32 cores, and on faceted surfaces runs approximately 12 hours on 64cores, and for each surface configuration there are 7 different intermediate reactant types, which results in 8 Nudged Elastic Band (NEB) calculations to account for the complete reaction path. Each NEB calculation requires 14 hours on 64 cores for flat surfaces, and 20 hours on 96 cores for faceted surfaces. Therefore, all together we expect to need (12*32+14*64)*10*8+(12*64+20*96)*3*8~167,000. (c) The thermodynamically favorable interface structure of TMDCs coated flat low-index Cu2O surfaces will be determined. The calculations involve large super cells, and we will consider 6 structures with different surface coating morphologies and coverages on both (100) and (110) surfaces. AIMD simulations will be used to anneal the interfacial structures, each requiring approximately 24 hours on 128cores, and the subsequent DFT relaxations and NEB calculations combined requires on 20 hours 96 cores for each of the 8 reduction reactions. All together we expect to need (24*128+20*96*8)*6*2 ~ 221,000. Industry partnership: Project URL: http://www.anl.gov/imaging/project/photo-integrated-imaging-understand-and-a... Requested allocation: 400000 Q1: 0 Q2: 0 Q3: 0 Q4: 400000 Justification: Storage requirements: The requester has used undetermined amount hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System