Keywords: water splitting, redox active ligand, transition metal complex, immobilization, oxygen evolution reaction
First row transition metal complexes attract attention as available alternatives to noble metals in water splitting catalysis. Irrespective of the system design – photocatalytic, photoelectrocatalytic, or photovoltaic coupled to electrocatalytic –, a co-catalyst component is expected to lower the kinetic energy barriers and make the chemical reaction steps energetically efficient. In this context, the endergonic oxygen evolution reaction (OER) is especially challenging, because it requires four consecutive electron and proton transfers in addition to the O-O bond formation, under demanding conditions.
Molecular catalysts and pre-catalysts can achieve high efficiency at the atomic level, but their practical use suffers from the eventual degradation of the organic ligands, complicated surface grafting, or redox instability of the compounds. We explored promising complexes containing hydrophobic and/or redox-active ligands that could assist in catalysis by solving one or more of the above complications. The demonstrated advantages of the new Cu- and Fe-containing compounds range from controllable, morphology preserving surface deposition [1,2], redox-active assistance of the ligand in catalysis [2,3], facilitated immobilization at the electrode surface via hydrophobic interactions [2,4] to operando precursor behavior leading to efficient catalytic films [2].
Acknowledgments
This work was funded by the National Research, Innovation and Development Office of Hungary, grant numbers NKFI-128841 and TKP2021-NKTA-05, RRF-2.3.1-21-2022-00009 and the National Key Research and Development Program of China (2018YFB1502003).
References
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[2] Benkó, T.; Lukács, D.; Frey, K.; Németh, M.; Móricz, M. M.; Liu, D.; Kováts, É.; May, N. V.; Vayssieres, L.; Li, M.; Pap, J. S. Catal. Sci. Technol. 2021, 11, 6411.
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[4] Al-Zuraiji, S. M.; Benkó, T.; Illés, L.; Németh, M.; Frey, K.; Sulyok, A.; Pap, J. S. J. Catal. 2020, 381, 615.