Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session G23: Invited Session: Fuels From Sunlight: Computational Studies of Photo-Electrodes and Catalysts |
Hide Abstracts |
Sponsoring Units: DCOMP Chair: Giulia Galli, University of California, Davis Room: 505-507 |
Tuesday, March 4, 2014 11:15AM - 11:51AM |
G23.00001: Electronic Excitations in Light Absorbers for Photoelectrochemical Energy Conversion: First Principles Calculations Based on Many-Body Perturbation Theory Invited Speaker: Yuan Ping The efficiency of photo-electrochemical cell for water splitting relies on the availability of Earth abundant, stable light absorbers with band gaps in the visible range, and band edges properly aligned with water redox potentials. We will present several ab initio calculations aimed at understanding and predicting the electronic properties of candidate photo-electrode materials [1]. Our calculations were carried out at different levels of theory, including density functional and many body perturbation theory (MBPT). We focused on WO$_3$ and CuW$_{1-x}$Mo$_x$O$_4$, and on functionalized Si wires for the photo-anode and photo-cathode, respectively. In particular, we will discuss how to decrease the band gap of WO3 by small molecule and rare gas atom intercalation [2,3], and by forming copper tungstate solid solutions [4]; in addition we will discuss how to improve band alignments with water redox potentials by considering phases of WO3 stable at high temperature [5]. Finally we will present calculations of absorption spectra of WO3 and silicon wires obtained using MBPT, by solving the Bethe Salpeter Equation, and we will present comparisons with recent experiments. \\[4pt] [1] Y. Ping, D. Rocca, G. Galli, Chem. Soc. Rev. 42, 2437 (2013).\\[0pt] [2] Y. Ping, Y. Li, F. Gygi, G. Galli, Chem. Mater., 24, 21, (2012).\\[0pt] [3] Q. Mi, Y. Ping, Y. Li, B. Cao, B. Brunschwig, P. Khalifah , G. Galli, H. Gary and N. Lewis, J.Am.Chem.Soc., 134, 44, (2012).\\[0pt] [4] J. Hill, Y. Ping, G. Galli and K. Choi, Energy Environ. Sci., 6, 2440 (2013).\\[0pt] [5] Y. Ping and G. Galli, submitted, 2013. [Preview Abstract] |
Tuesday, March 4, 2014 11:51AM - 12:27PM |
G23.00002: Oxide/Water Interfaces: How the Surface Chemistry Modifies the Electronic Energy Alignment Invited Speaker: Michiel Sprik The minimum of the $d$-electron conduction band of an aqueous transition metal oxide electrode is typically no more than a few 100 mV away from the standard hydrogen electrode (SHE). Because of this favourable alignment of the electronic energy levels (near) metallic transition metal oxides with partly filled $d$ bands can be used as electrocatalysts while the compounds with finite electronic gap can be used as photocatalysts. However, because of their ionic character, transition metal-oxide surfaces also show amphiphilic acid-base activity. At low pH the basic sites are protonated and at high pH the acidic sites deprotonated creating an electrical double layer with corresponding surface potential. The alignment of the electronic energy levels, and by implication their redox activity, is therefore pH dependent. In fact, even in absence of protonic surface charge, the coordination with water molecules is already capable of shifting the electronic energy levels of the oxide by 1 eV or more. Computation of the electronic energies in transition metal oxide electrodes requires therefore a detailed modeling of their aqueous surface chemistry. The solvation energy of the proton is the common energy reference for both redox potentials on the SHE scale and acidity constants (pKa). Computation of the H$^+$ solvation energy is therefore a key component in a unified treatment of redox and acid-base chemistry. In this talk we outline the Density Functional Theory based Molecular Dynamics (DFTMD) method we have developed for this purpose [1,2]. The central tool of our approach is a method for reversible insertion of protons in the aqueous part of the DFTMD model system. As an illustration we discuss the application to the rutile TiO$_2$/water and MnO$_2$/water interface. \\[4pt] [1] Cheng, J.; Sulpizi, M.; VandeVondele, J.; Sprik, M. ChemCatChem 4 (2012) 636.\\[0pt] [2] Cheng, J.; Sprik, M. Phys. Chem. Chem. Phys 14 (2012) 11245. [Preview Abstract] |
Tuesday, March 4, 2014 12:27PM - 1:03PM |
G23.00003: Cobalt, nickel/iron, and titanium oxide electrodes for water oxidation Invited Speaker: Annabella Selloni Water splitting on metal oxide surfaces has attracted enormous interest for more than forty years. While a great deal of work has focused on titanium dioxide (TiO$_{\mathrm{2}})$, recently cobalt and mixed Ni-Fe oxides have also emerged as promising electrocatalysts for water oxidation due to their low cost and high activity. In this talk I shall discuss various aspects of water oxidation on cobalt (hydro-)oxides, pure and mixed nickel and iron (hydro-)oxides, and TiO$_{\mathrm{2\thinspace }}$surfaces. Using DFT$+$U calculations, I shall examine the composition and structure of cobalt and Ni-Fe oxides under electrochemical conditions, and present studies of the oxygen evolution reaction (OER) on the relevant stable compounds. I shall also present hybrid functional calculations of the first proton-coupled-electron transfer at the water/TiO$_{\mathrm{2}}$ interface in the presence of a photoexcited hole. Our results provide evidence that the proton and electron transfers are not concerted but rather represent two sequential processes. They also suggest that the OER is faster at higher pH, as indeed observed experimentally. [Preview Abstract] |
Tuesday, March 4, 2014 1:03PM - 1:39PM |
G23.00004: From Electronic Structure to Catalytic Activity: Descriptors for water splitting reactions Invited Speaker: Aleksandra Vojvodic |
Tuesday, March 4, 2014 1:39PM - 2:15PM |
G23.00005: Nonadiabatic Dynamics of Photoinduced Proton-Coupled Electron Transfer Processes in Solution Invited Speaker: Alexander Soudackov Theoretical approaches developed to elucidate the fundamental principles underlying the nonequilibrium dynamics of photoinduced proton-coupled electron transfer (PCET) processes in solution will be presented [1-3]. These processes are simulated by propagating nonadiabatic surface hopping trajectories on electron-proton vibronic surfaces that depend on the solute and solvent nuclear coordinates. The solvent is represented either as explicit solvent molecules or as a dielectric continuum. In the latter case the solvent dynamics is described in terms of two collective solvent coordinates corresponding to the energy gap coordinates associated with electron and proton transfer. Calculations on model systems reveal two distinct solvent relaxation timescales, where the faster timescale relaxation corresponds to librational motions of solvent molecules in the first solvation shell and the slower time scale corresponds to the bulk solvent dielectric response. These calculations illustrate that the charge transfer dynamics, solvent dynamics, and vibrational relaxation processes are strongly coupled. Extensions of the methodology and applications to experimentally relevant systems will also be discussed [4]. \\[4pt] [1] Hazra, A.; Soudackov, A. V. and Hammes-Schiffer, S. J. Phys. Chem. B 114, 12319--12332 (2010). \newline [2] Soudackov, A. V.; Hazra, A. and Hammes-Schiffer, S. J. Chem. Phys. 135, 144115 (2011). \newline [3] Auer, B.; Soudackov, A. V. and Hammes-Schiffer, S. J. Phys. Chem. B 116, 7695--7708 (2012). \newline [4] Ko, C.; Solis, B. H.; Soudackov, A. V. and Hammes-Schiffer, S. J. Phys. Chem. B 117, 316--325 (2013). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700