Publications (2)3.57 Total impact
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ABSTRACT: Porphyrin is a very important component of natural and artificial catalysis and oxygen delivery in blood. Here, we report that, based on first-principles density-functional calculations, a hydrogen molecule can be adsorbed non-dissociatively onto Ti-, V-, and Fe-porphyrins, similar to oxygen adsorption in heme-containing proteins, with a significant energy gain, greater than 0.3 eV per H(2). The dihydrogen-heme complex will be non-magnetic, as is oxyhemoglobin. In contrast to the backward electron donation of Fe(III)-O(2)(-) in oxyhemoglobin, the dihydrogen binding originates from electron donation from H(2) to the Fe(II). We have identified that the local symmetry of the transition metal center of porphyrins uniquely determines the binding strength, and, thus, one can even manipulate the strength by intentionally and systematically breaking symmetry.Physical Chemistry Chemical Physics 12/2009; 11(48):11400-3. · 3.57 Impact Factor
Article: Divacancy-nitrogen-assisted transition metal dispersion and hydrogen adsorption in defective graphene: A first-principles study[show abstract] [hide abstract]
ABSTRACT: We propose a route to dispersing hydrogen-adsorbing transition metals (TMs) on a large scale onto vacancy-engineered defective graphenes by employing natural carbon-nitrogen-TM complexes, i.e., TM-containing porphyrins. Based on first-principles density-functional calculations, the TM-porphyrin core—made of one central TM and four surrounding nitrogen atoms—can be effectively generated by three defect-engineering processes of graphenes: (1) creation of carbon divacancies, (2) nitrogen substitution of unsaturated carbons, and (3) TM incorporation. The atomistically dispersed Sc, Ti, and V are able to adsorb hydrogen molecules as strongly as 0.2–0.4 eV with the Kubas coordination. The Fe-porphyrin-like unit in graphenes can also have the Kubas adsorption of hydrogen, if the exchange splitting is reduced by a compressive in-plane strain.Phys. Rev. B. 81(8).