Enhancing Oxygen Evolution Reaction through In Situ Electrochemical Oxidation for the Structural Control of Co-Fe Prussian Blue Analogue

The development of exceptionally efficient catalysts for the oxygen evolution reaction (OER) and gaining a deep understanding of their activity is essential for advancing electrochemical conversion technologies. Prussian blue analogues (PBAs) serve as promising pre-catalysts for the OER. However, PBAs, typically prepared through the conventional co-precipitation method, exhibit a lower active site density and limited electrical transport, making them suitable precursors for the derivation of PBA derivatives. In this research, we identified a significant enhancement in the electrocatalytic performance of Co-Fe Prussian blue analogue (CoFe PBA) through electrochemical oxidation. The cubic CoFe PBA was synthesized by one-step co-precipitation method using adjusting the amount of sodium citrate and potassium ferricyanide. After the electrochemical treatment, CoFe PBA demonstrates remarkable attributes, including a low overpotential of 331mV at a current density of 10mA·cm-2, a small Tafel slope of 50.4mV·dec-1, and excellent long-term stability during electrolysis in a 1M KOH alkaline medium for over 37h. Moreover, the electrochemical oxidation of CoFe PBA was comprehensive, employing techniques such as Transmission electron microscope, Powder X-ray diffraction, and X-ray photoelectron spectroscopy. These analyses confirmed the presence of real active substances, including CoOOH and a part of FeOOH species, further supporting the observed improvements in electrocatalytic activity.