Electrodeposition of Fe-Complexes on Oxide Surfaces for Efficient OER Catalysis

Sahir M Al-Zuraiji,Tímea Benkó,József S Pap,Krisztina Frey,Zsolt Kerner

doi:10.3390/catal11050577

Sahir M Al-Zuraiji, Tímea Benkó + Show 3 more

Open Access

https://doi.org/10.3390/catal11050577

Copy DOI

Journal: Catalysts	Publication Date: Apr 30, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: Óbuda University, Centre for Energy Research

Abstract

Progress in non-covalent/self-assembled immobilization methods on (photo)electrode materials for molecular catalysts could broaden the scope of attainable systems. While covalent linkage (though considered more stable) necessitates functional groups introduced by means of often cumbersome synthetic procedures, non-covalent assemblies require sufficient propensity of the molecular unit for surface adsorption, thus set less rigorous pre-requisites. Herein, we report efficient electrodeposition (ED) of two Fe(III) complexes prepared with closely related NN’N pincer ligands yielding stable and active ad-layers for the electrocatalysis of the oxygen-evolving reaction (OER). The ED method is based on the utilization of a chloride precursor complex [FeIIICl2(NN’N)], which is dissolved in an organic electrolyte undergoes chloride/aqua ligand exchange upon addition of water. ED provides patchy distribution of a chloride-depleted catalyst layer on indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) surfaces, which can be applied for long periods as OER electrocatalysts. Compared to drop-casting or layering of [FeIIICl2(NN’N)] with Nafion (a commonly used support for molecular electrocatalysts), the surface modification by ED is a material saving and efficient method to immobilize catalysts.

Highlights

Electrochemical water splitting is considered to be an important technology, consented to suppress the usage of fossil fuels since it can help to overcome the storage-reuse obstacles of renewable-based energy systems by producing the green energy carrier H2 [1,2]
Electrocatalysts for the oxygen-evolving reaction that utilize non-precious metals and efficient immobilization methods can be very useful to the progress of artificial photosynthesis and water electrolysis systems
We presented a simple electrodeposition method that allowed us to immobilize [FeIIICl2(BAI)] precursor complexes bearing aromatic NN’N pincer ligands from a suitable water/organic mixture

Summary

Introduction

Electrochemical water splitting (electrolysis of water) is considered to be an important technology, consented to suppress the usage of fossil fuels since it can help to overcome the storage-reuse obstacles of renewable-based energy systems by producing the green energy carrier H2 [1,2]. The complete reaction in Equation (1) necessitates efficient water oxidation catalysts (WOCs) as functional components of the overall system. A WOC is meant to enhance the efficiency of the oxygen-evolving reaction (OER) aiding solar-to-chemical energy conversion as in the artificial photosynthesis concept [3]. The OER from water in Equation (2) is kinetically sluggish, involving the transfer of four electrons and four protons. As a consequence, it means a bottleneck for the overall splitting reaction, where the electrons and protons generated by the anodic OER are used up for the respective formation of H2 in the cathodic reaction in Equation (3), requiring much lower kinetic overpotential [4]: 2H2O(l) → O2(g) + 2H2(g) (1). Polycyclics are expected to limit solubility, and the effectiveness of the drop-casting technique that was found suitable for complex 1 and some other Fe-complex precursors earlier [29]

Objectives

Methods

Findings

Conclusion