Atomic scale computer simulations can provide access to the microscopic processes occurring at electrode surfaces and can thereby contribute enormously to the understanding of electrochemical reactions. Despite the fact that the research field of experimental electrochemistry is about two centuries old, it is just within the last few years that computer simulations have reached the point at which they can describe the complicated ionic interactions and electron transfer reactions taking place in an electrochemical cell. Due to the environmental problems originating from the use of fossil fuels an increasing political pressure is calling for an alternative energy economy. Here electrochemical fuel cells are a promising candidate.
By using theoretical tools, such as density functional theory, we can calculate, e.g. the free energy reaction landscape and predict reaction mechanisms of electrochemical reactions. By using suitable descriptors, such as the free energy of adsorption for hydrogen or oxygen, density functional theory can now also play an important role in combinatorial screening of electrode materials in the search for promising catalysts for various electrochemical reactions, e.g. the hydrogen evolution reaction or the oxygen reduction reaction.
The theoretical tools currently used by the theoretical electrochemistry group at CAMd are the density functional theory (DFT), the nudged elastic band method, Monte Carlo methods and statistical mechanics. We are developing and maintaining a plane waves based pseudo-potential DFT code and a real-space grid DFT code with the projected augmented wave (PAW) formalism. In order to describe specific systems at a more accurate level, we are working on implementations of van der Waals interactions and electron localization (exact exchange, hybrid functionals and self-interaction correction).
The main research focus in the theoretical electrochemistry group is to obtain trends in electro-catalysis and recently we have started to create a more detailed model of the electron transfer reaction in electrochemical cells. We are working in close collaboration with the experimental electrochemistry group at the Center for Individual Nanoparticle Functionality (CINF), located in the same building at the DTU campus. The systems, reactions and projects that we are mostly interested in are:
- PEM Fuel Cells (hydrogen oxidation and oxygen reduction)
- Electrolysis (hydrogen evolution and water oxidation)
- Solid Oxides Fuel Cells
- Batteries
- Photo-catalysis
- Enzyme-catalysis
- Censors
- Electron Localization (exact exchange, hybrid functionals and self-interaction correction)
- Data Base Tool Kit
Contact persons
Professor Jens K. Nørskov, CAMd director
Recent highlights
Figure 1: Volcano plot of the measured catalytic activity of the oxygen reduction reaction for various transition metal electrodes as a function of the calculated binding energy of oxygen atoms from DFT calculations. In this publication, the origin of the overpotential for oxygen reduction at a fuel cell cathode was identified and a simple model was introduced to calculate the free energy landscape of any electrochemical reaction as a function of applied electrode potential. For further details see: J. K. Nørskov, J. Rossmeisl, A. Logadottir, L. Lindqvist, J. R. Kitchin, T. Bligaard and H. Jónsson, J. Phys. Chem. B 108, 17886 (2004)
Figure 2: Pareto-optimal plot of stability and activity of surface alloys for the hydrogen evolution reaction (HER). In this publication, a density functional theory based calculations for a high-throughput screening scheme are presented that successfully identifies a new electrocatalyst for the HER. The activity of over 700 binary surface alloys is evaluated theoretically and the stability of each alloy in electrochemical environments is also estimated. BiPt is found to have a predicted activity comparable to, or even better than, pure Pt, the archetypical HER catalyst. This alloy is synthesized and tested experimentally and shows improved HER performance compared with pure Pt, in agreement with the computational screening results. For further details see: J. Greeley, T. F. Jaramillo, J. Bonde, I. Chorkendorff and J.K. Nørskov, Nature Materials 5, 909 (2006)
Figure 3: A Pt(111) electrode surface in water environment. A detailed model of the hydrogen evolution reaction (HER) is introduced. All the elementary reaction barriers in HER (the Volmer, Tafel and Heyrovsky reactions) are calculated with the Density Functional Theory with the Nudged Elastic Band method and a new method of varying the electrode potential is introduced. It is confirmed with explicit calculations that the electrochemical transfer coefficient can be viewed as a manifestation of the Brønsted-Evans-Polanyi-type relationship. For further details see: E. Skúlason, G. S. Karlberg, J. Rossmeisl, T. Bligaard, J. Greeley, H. Jónsson, J. K. Nørskov, Phys. Chem. Chem. Phys. 9, 3241 (2007)
Figure 4: Cyclic Voltammograms from first principles calculations for H adsorption and desorption from Pt(111) and Pt(100) surfaces at different temperatures. The top panels show the results from an analytical model and the bottom two show results from a Metropolis Monte Carlo simulation. Cyclic voltammetry is a fundamental experimental tool for characterizing electrochemical surfaces. Whereas cyclic voltammetry is widely used within the field of electrochemistry, a way to quantitatively and directly relate the cyclic voltammogram to ab initio calculations has been lacking until now. In this article, the cyclic voltammogram and charge deposition as a function of potential is derived based solely on density functional theory calculations and standard molecular tables. This first principle approach is in excellent agreement with experimental results, both qualitatively and quantitatively. This link between surface science and electrochemistry will hopefully open up great possibilities of studying new electrode materials with ab initio calculations for e.g. fuel cells applications. For further details see: G. S. Karlberg, T. F. Jaramillo, E. Skúlason, J. Rossmeisl, T. Bligaard, J. K. Nørskov, Phys. Rev. Lett. 99, 126101 (2007)
Recent Publications
2007:
G. S. Karlberg, T. F. Jaramillo, E. Skúlason, J. Rossmeisl, T. Bligaard, J. K. Nørskov: Cyclic voltammograms on Pt(111) and Pt(100) from first principles, Phys. Rev. Lett. 99, 126101 (2007)
J. Greeley, J.K. Nørskov: Electrochemical dissolution of surface alloys in acids: Thermodynamic trends from first-principles calculations, Electrochim. Acta 52, 5829 (2007)
E. Skúlason, G. S. Karlberg, J. Rossmeisl, T. Bligaard, J. Greeley, H. Jónsson, J. K. Nørskov: Density functional theory calculations for the hydrogen evolution reaction in an electrochemical double layer on the Pt(111) electrode, Phys. Chem. Chem. Phys. 9, 3241 (2007)
T. Bligaard, J.K. Nørskov: Ligand effects in heterogeneous catalysis and electrochemistry , Electrochim. Acta 52, 5512 (2007)
J. Greeley, J.K. Nørskov: Large-scale, density functional theory-based screening of alloys for hydrogen evolution, Surf. Sci. 601, 1590 (2007)
2006:
J. Rossmeisl, Z.-W. Qu, H. Zhu, G.-J. Kroes and J.K. Nørskov: Electrolysis of water on oxide surfaces, accepted in J. Electroanalytical Chem. (2006)
B. Hinnemann, and J.K. Nørskov: Catalysis by enzymes: The biological ammonia synthesis, Top. Catal. 37, 55 (2006)
J. Rossmeisl, J.K. Nørskov, C.D. Taylor, M.J. Janik and M. Neurock: Calculated Phase Diagrams for the Electrochemical Oxidation and Reduction of Water Over Pt, J. Phys. Chem. B. 101, 21833 (2006)
V. Stamenkovic, B.S. Moon, K.J.J. Mayrhofer, P.N. Ross, N.M. Markovic J. Rossmeisl, J. Greeley, J.K. Nørskov: Changing the activity of electrocatalysts for oxygen reduction by tuning the surface electronic structure, Angewandte Chemie International Edition 45, 2897 (2006) (VIP-paper and Front page)
J. Greeley, T. F. Jaramillo, J. Bonde, I. Chorkendorff, J. K Nørskov: Computational high-throughput screening of electrocatalytic materials for hydrogen evolution, Nature Materials 5, 909 (2006)
J. K. Nørskov, and C. H. Christensen: Chemistry Toward efficient hydrogen production at surfaces, Science 312, 5778 (2006)
J. Greeley, J. K. Nørskov, L. A. Kibler, A. M. El-Aziz, and D. M. Kolb: Hydrogen evolution over bimetallic systems - understanding the trends, Chem. Phys. Chem. 7, 5 (2006)
2005:
J.C. Davies, J. Bonde, Á. Logadóttir, J.K. Nørskov, and I. Chorkendorff: The Ligand Effect: CO desorption from Pt/Ru catalysts, Fuel Cells 5, 429 (2005)
J. Greeley and J.K. Nørskov: A general scheme for the estimation of oxygen binding energies on binary transition metal surface alloys, Surf. Sci. 592, 104 (2005)
I.N. Remediakis, N. Lopez and J.K. Nørskov: CO oxidation on rutile-supported Au nanoparticles, Angew. Chemie Int. Ed. 44, 1824 (2005)
I.N. Remediakis, N. Lopez, and J.K. Nørskov: CO oxidation on gold nanoparticles: Theoretical studies, Appl. Catal. A 291, 13 (2005)
B. Hinnemann, P. G. Moses, J. Bonde, K. P. Jørgensen, J. H. Nielsen, S. Horch, I. Chorkendorff, and J. K. Nørskov: Biomimetic hydrogen evolution, J. Am. Chem. Soc. 127, 5308 (2005)
J. Rossmeisl, A. Logadottir, J.K. Nørskov: Electrolysis of water on (oxidized) metal surfaces, Chemical Physics 319, 178 (2005)
J. K. Nørskov, T. Bligaard, A. Logadottir, J.R. Kitchin, J. G. Chen, S. Pandelov, and U. Stimming: Trends in the exchange current for hydrogen evolution, J. Electrochem. Soc. 152, J23 (2005)
2004:
J. Meier, J. Schiøtz, P. Liu, J.K. Nørskov, and U. Stimming: Nano-scale effects in electrochemistry, Chem. Phys. Lett. 390, 440 (2004)
J.C. Davies, R.M. Nielsen, L.B. Thomsen, I. Chorkendorff, Á. Logadóttir, Z. Lodziana, J.K. Nørskov, W. Li, B. Hammer, S.R. Longwitz, J. Schnadt, E.K. Vestergaard, R.T. Vang, and F. Besenbacher: CO desorption rate dependence on CO partial pressure over Pt fuel cell catalyst, Fuel Cells 4, 309 (2004)
B. Hinnemann , and J.K. Nørskov: Structure and mechanism of the FeFe-cofactor of the iron-only nitrogenase, Phys. Chem. Chem. Phys. 6, 843 (2004)
B. Hinnemann, and J.K. Nørskov: The chemical activity of the nitrogenase FeMo cofactor with a central nitrogen ligand A density functional study, J. Am. Chem. Soc. 126, 3920 (2004)
J. Rossmeisl, J.K. Nørskov, and K.W. Jacobsen: Elastic effects behind cooperative bonding inb -sheets, J. Am. Chem. Soc. 126, 13140 (2004)
J.K. Nørskov, J. Rossmeisl, A. Logadottir, L. Lindqvist, J. Kitchin, T. Bligaard and H. Jónsson: The origin of the overpotential for oxygen reduction at a fuel cell cathode, J. Phys. Chem. B 108, 17887 (2004)