Immobilization and characterization of water-insoluble fe complexes as molecular catalysts for water oxidation

Abstract

The apparent difference between the expanding consumption of fossil fuels and chemicals and the limited amount of resources has motivated many researchers to seek solutions for maintaining the sustainability of our community. Artificial photosynthesis (AP), which utilizes sunlight to produce high-value chemicals, including H2 from abundant resources, is regarded as the most encouraging and viable method. Modern AP systems necessitate in the first place to develop inexpensive, highly active, and stable catalysts for hydrogen production (Hydrogen Evolving Reaction, HER) and water oxidation (Oxygen Evolving Reaction, OER), both are a crucial challenge. However, prior to implementing any artificial systems on water-splitting catalysts that generate oxygen from water without extreme driving potentials are demanded. Many recent studies concentrate on molecular systems based on the highly abundant first-row transition metals (TMs) proper as water oxidation catalysts (WOCs) due to their structural versatility, transparent catalytic mechanisms, and ultimate atomic efficiency concerning catalytic centers. Herein, we report Fe- based compounds among these TMs as efficient electrocatalysts for OER. In this context, we studied the electrochemical behaviour of water-insoluble Fe complexes in homogeneous water/organic mixtures to reveal their intrinsic molecular properties. The water-insolubility of the selected Fe complexes allowed for simple immobilization methods (dip-coating and drop-casting) on model semiconductors. Ultimately, electrodeposition has been explored to reduce to a minimum amount of the complex required for long-term operando stability. The consequence of these studies is that water-insolubility presents a viable strategy for designing new molecular catalyst/(photo)anode hybrids.