1 Facultad de Química y Biología, Universidad de Santiago de Chile. Avenida Libertador Bernardo O’Higgins 3363, Estación Central, Santiago, Chile. 2 Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Porto Alegre, 91501-970, RS, Brazil. Institute of Physics, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Porto Alegre, 91501-970, RS, Brazil. 3 Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago (Chile). 4 Laboratorio de Química Teórica Computacional (QTC), Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago 9900087
Corresponding Author: jose.zagal@usach.cl
We have been able to tune the electrocatalytic activity of iron phthalocyanine (FePc) and iron hexadodecachlorophthalocyanine (16(Cl)FePc) for the oxygen reduction reaction (ORR) by the “pull effect” of pyridinium molecules, which play both the role of molecular anchors and also of and axial ligand for FePc. Pull effect is caused by the positive charge located on the core pyridinium. We have explored the influence of the core positions (Up or Down), in two structural pyridiniums isomers on the activity for the RRO of FePc and 16(Cl)FePc. Of all self-assembled systems tested, the ORR catalytic activity was highest for Au(111)/pyridinium-Up/FePc system. XPS measurements and DFT calculations showed that is possible to tune the FePc-N(Pyridiniums) and Fe-O2 binding energies, by changing the core positions and affecting “pull effect” in pyridiniums, this has a direct effect on the activity of FePcs. Plot of activity as (log I)E versus the calculated Fe-O2 binding energies gives a volcano correlation indicating that an optimum binding energy of O2 with the Fe center provides the highest activity in agreement with previous findings [1] using MN4s adsorbed on graphite.
Acknowledgements: The authors are grateful to PAI-CONICYT 79150041. Fondecyt 1140192, C.G-C. Fondecyt Postdoctoral Project 3150674. D.C-A thanks ICM grant #120082. Powered@NLHPC: NLHPC (ECM-02). Millennium Project RC120001, Fondecyt 1140199, and Dicyt-USACH, LNLS (Brazil) for the use of beamline (SXS - 18986).
References:
1. Zagal, J. H.; Koper, M. T. M. Angew. Chemie Int. Ed. 2016, 55 (47), 14510–14521.