Structure and catalytic activity of metalloporphyrin networks

D. GRUMELLI; H. F. BUSNENGO; R. GUTZLER; P. ABUFAGER; J. M. LOMBARDI; K. KERN

Seminario; Gordon Research Seminar on Dynamics at Surfaces (GRS); 2019

Porphyrins are organic molecules which play a vital role in nature1. For instance, the heme-group of hemoglobin has a porphyrin complex in the center responsible for oxygen transport, porphyrines act as heme cofactor of cytochromes, and other redox active enzymes and are also photosensitizers. Inspired by its relevance in nature and due to the general believe that systems might be promising candidates for future organic devices, the surface chemistry of porphyrins is an area of increasing appeal2,3. The versatility of the porphyrins toward a proper choice of the metal central ion opens a wide field of potential applications going from molecular electronic and spintronic to catalysis1. Moreover, additional functionalization emerges by a proper choice of the peripheric functional groups.Surface-supported porphyrins adsorb on the surface predominantly with the macrocycle parallel to the surface plane. The balance between intermolecular interactions and porphyrin-substrate interactions governs the self-assembly process of the 2D molecular network. Different packings where proposed for metalloporphyrins on noble metal surfaces (see refs 1,4 and references therein). Recently, it was shown that the sublimation of a second metal to the network leads to a partial replacement of the initial metal center in the macrocycle5. The effect of this second metal on the catalytic properties of the resulting mixed SAM is not fully understood.In this work, we theoretically scrutinized the SAM structure of M1TPyP/Au(111) (M1 = Fe, Co) and the resulting mixed SAM obtained after evaporation of a second metal M2=Fe,Co (M1TPyP+M2/Au(111)). The role played by intermolecular and molecule-substrate interactions on the SAM properties is analyzed. Afterwards, the catalytic properties of FeTPyP and FeTPyP+Co towards the oxygen reduction (ORR) and evolution (OER) reactions is investigated in order to shed light into the microscopic factors behind the different catalytic activities experimentally observed for these systems6. References1 W. Auwärter, D. Écija, F. Klappenberger and J. V. Barth, Nature Chemistry, 7, 105 (2015).2 K. Ladomenou, T. N. Kitsopoulos, G. D. Sharma, and A. G. Coutsolelos, RSC Adv. 4, 21379 (2014).3 M. Zhao, S. Ou, and C.-D.Wu, Acc. Chem. Res., 47, 1199 (2014).4 J. M. Gottfried, Surface Science Reports 70, 259 (2015).5 D. Hötger, P. Abufager, C. Morchutt, P. Alexa, D. Grumelli, J. Dreiser, S. Stepanow, P. Gambardella, H. F. Busnengo, M. Etzkorn, R. Gutzler, K. Kern6 D. Hötger, M. Etzkorn, C. Morchutt, B. Wurster, J. Dreiser, S. Stepanow, D. Grumelli, R. Gutzler, K. Kern Physical Chemistry Chemical Physics 21, 2587 (2019)