Cobalt Colloid-derived Efficient and Durable Nanoscale Electrocatalytic Films for High-Activity Water Oxidation

Oxygen evolution reaction is of immense importance and is vitally necessary for devices such as electrolyzers, fuel cells, and other solar and chemical energy conversion devices. The major challenges that remain in this quest are due to the lack of effective catalytic assemblages operating with optimum efficiency and obtainable following much simpler setups and easily accessible methods. Here, we demonstrate that the robust electrocatalytic activity toward water oxidation can be achieved employing straightforwardly obtainable nanoscale electrocatalysts derived from easily made colloidal-cobalt nanoparticles (Co-CNPs) prepared in clean carbonate systems. Thin-film non-noble metal nanoscale electrocatalysts such as simple Co-CNPs/FTO and annealed Co-CNPs/FTO₂₅₀ and Co-CNPs/FTO₅₀₀ obtained by depositing Co-CNPs on the FTO substrate are shown to initiate water oxidation at much lower overpotentials such as just 240 mV for Co-CNPs/FTO₂₅₀ under mildly alkaline conditions while demonstrating an impressive Tafel slope of just 40 mV dec^-1. Furthermore, the robust catalyst demonstrated a high electrochemical surface area of 91 cm² and high turnover frequency and mass activity of 0.26 s^-1 and 18.84 mA mg^-1, respectively, just at 0.35 V, and superior durability during long-term electrolysis. These outstanding catalytic outcomes using easily prepared Co-CNPs/FTO₂₅₀-type catalytic systems are comparable and even better than other noble and non-noble metal-based nanoscale catalytic assemblages obtained by much difficult methods. Most advantageously, the colloidal route also offers the easiest approach of incorporating carbon contents in the catalytic layer, which can ultimately increase mechanical stability and mass transfer capability of the system.