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: Ryan Hadt Applicant's institution: ANL Applicant's division: CSE Project Name: HER_OER Project title: Geometric and electronic structure contributions to oxygen and hydrogen evolution reactions Associated funding: Enrico Fermi Fellowship to Ryan Hadt & DOE Division of Chemical Sciences, Geosciences, and Biosciences Other Systems: N/A Science: This work focuses on elucidating electronic structure contributions to hydrogen and oxygen evolution reactions (HER and OER, respectively), as carried out by molecular and heterogeneous systems. In both the HER and OER, proton coupled electron transfer (PCET) is thought to allow for ‘redox-leveling’, which can potentially contribute to reactivity by generating reactive intermediates at relatively low overpotentials. Additionally, the intermediates generated just before the rate-determining step (i.e., H-H or O-O bond formation) are typically unique species that are rarely observed experimentally. Thus, this proposal will focus on two main aims: 1) calculating the redox potentials and pKas of the key molecular species involved in the catalytic cycles of H-H and O-O bond formation, and 2) calculating and defining the electronic structures of the key intermediates involved in H-H and O-O bond formation. These calculations will be directly correlated to experimental data obtained in our laboratory as well as the Advanced Photon Source and other light-sources (e.g., Linac Coherent Lightsource (LCLS)). The combined experimental and computational results will define geometric and electronic structure contributions to the key reactions involved in solar energy storage. Project description: Our focus is currently on understanding the geometric and electronic structure contributions to the formation of low- and high-valent intermediates involved in the HER or OER. In the former, this typically involves the protonation of highly reduced metal centers to form metal-hydride species. The metal-hydride species can be protonated again to evolve hydrogen. However, the mechanism of H-H bond formation is not well defined, and can involve homolytic or heterolytic pathways. In OER, high-valent metal-oxo species can react through radical coupling, H-atom abstraction from water, or nucleophilic attack. We will therefore focus on better understanding the geometric and electronic structures of the low- and high-valent precursors as well as catalytically active species and how these contribute to the various mechanisms of H-H and O-O bond formation. Our research also involves the direct spectroscopic characterization of the precusors to the catalyticall y active. Thus, these calculations can be directly correlated and compared to experimental data. The specific calculations will be carried out as follows. We will run gas-phase DFT geometry optimizations on all key species involved in catalytic cycles. Frequency and wave function stability checks will be required for all geometries. Single point calculations will be carried out to determine DFT energies at the basis set limit. This will allow for the calculation of redox potentials and pKas. Additional single point calculations (including time-dependent DFT) will be carried out to directly correlate the electronic structure to experimental data (e.g., UV-vis, electron paramagnetic resonance (EPR), X-ray absorption and emission (XAS/XES)). Lastly, potential energy surfaces (PESs) will be carried out to directly monitor electronic structure evolution during bond-forming and bond-breaking reactions. PES generation will involve a series of constrained geometry optimizations around the transition state, and thus requires the same calculations as indicated above for ground state species. All geometry optimizations, frequency calculations, and stability checks will be carried out in Gaussian09 (G09). Single point energy calculations will also be carried out using G09. Orca 3.0.3 is an imperative program for the calculation of UV-vis, EPR, XAS, and XES parameters for direct comparison to our experimental data. Our experience indicates that ~40,000 CPU hours are necessary for geometry optimizations of ground states and PESs, ~20,000 CPU hours are necessary for frequency calculations and transition state searches, ~10,000 CPU hours are necessary of stability checks, and ~30,000 CPU hours are necessary for additional single point energy and properties calculations. Thus, we request 100,000 CPU hours. Industry partnership: N/A Project URL: http://blogs.anl.gov/solar-energy/ Requested allocation: 100000 Q1: 25000 Q2: 25000 Q3: 25000 Q4: 25000 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