An Assessment of Theoretical Methods for Homogeneous Nickel Catalysts for H2 Oxidation and Production
December 2010
The rational design of improved catalysts requires a detailed molecular-level understanding of the energetic and mechanistic factors controlling the activity of existing catalysts. We aim to determine and predict accurately, through computations, the thermodynamic properties and proton and electron movement for catalysts developed in the Energy Frontier Research Center for Molecular Electrocatalysis, in particular the Ni(P2N2)22+ catalysts for H2 oxidation and evolution. These catalysts are mononuclear nickel complexes that include cyclic diphosphine ligands with amine bases incorporated in the ligands. The presence and positioning of the amine bases near the metal center is the critical structural feature for the activity and the efficiency of these catalysts, as these bases facilitate the heterolytic cleavage or formation of the H-H bond while acting as proton relays in the management of the proton and electron movement during the catalytic cycle.
In this paper, we benchmarked a number of commonly used density functional theory (DFT) and electron-correlated molecular orbital theories in their ability to describe the free energy profile for H2 oxidation/evolution, i.e., the formation of an H2 adduct complex, of proton-hydride and di-proton intermediates, and the transition states between them. We found that DFT functionals B3P86, M06, and PBE show good accord with CCSD(T) calculations, while other widely used functional do not perform nearly as well.
Reference: Chen S, S Raugei, R Rousseau, M Dupuis, and RM Bullock. 2010. "Homogeneous Ni Catalysts for H2 Oxidation and Production: An Assessment of Theoretical Methods, from Density Functional Theory to Post Hartree-Fock Correlated Wave-Function Theory." Journal of Physical Chemistry A 114(48), 12716-12724. DOI: 10.1021/jp106800n
