The increasing consumption of fossil fuels to fulfil the constant growth of the global energy demand have led to the unceasing accumulation of CO₂ in the atmosphere and, consequently, to the global warming of our planet. The fight against this consequent climate change relies on the development of new energy conversion schemes based on sustainable carbon-free energy sources.[1] One of the most attractive and feasible solutions to this challenge is the production of H₂ as an energy carrier through catalytic water splitting (WS).

Common WS electrolysers work in a division of labour approach where the two constituting half-reactions, namely the oxygen evolution reaction (OER, 2H₂O → O₂ + 4H⁺ + 4e⁻, 1.23 V_NHE) and the hydrogen evolution reaction (HER, 2H⁺ + 2e⁻ →H₂, 0 V_NHE), take place in separate compartments. Both half-reactions require the use of catalysts to decrease their activation energies and increase the associated reaction rates. Being the OER particularly demanding from both thermodynamic and kinetic points of view, the development of efficient, robust and easy to engineer electrodes based on earth-abundant metals is particularly challenging. First-row transition metal based oxides/hydroxides have attracted enormous attention in the last decade.[2] Among them, Co-containing nanocatalysts arise as promising alternatives to noble-metal based OER anodes. However, non-supported cobalt oxide/hydroxide nanocatalysts suffer from low conductivity[3] and fast agglomeration under OER turnover conditions.[4][5] To overcome this shortcomings, in this work, conductive carbon supports were used to obtain supported Co-based nanoparticles.

The performance of OER anodes based on supported nanocatalysts is highly dependent on the interactions taking place at the interface between the nanocatalyst and the employed conductive support. To this end, the organometallic approach was used in this work for the synthesis of metal-based nanostructures, preparing electrodes of tailored nanocatalyst–support interactions. A set of OER working electrodes based on Co(OH)₂ nanoparticles (NPs) and carbon microfibers (CFs) were prepared. The obtained systems differ in either the stabilizer present at the surface of the NPs (THF or 1-heptanol), the surface functionalization of the used CFs (bare CFs or oxidized-CFs) and the growth of the NPs in the presence (in-situ) or the absence (ex-situ) of the carbonaceous support. Correlation of a detailed structural and compositional analysis with the electroactivity of the tested nanomaterials allows extracting valuable insights about the influence of the metal–support interface on their overall OER performances.