Achieving High OER Performance by Tuning the Co/Mn Content in Prussian Blue Analogues

The need for efficient, economical, and clean energy systems is increasing, and as a result, interest in water-splitting techniques to produce green hydrogen is also increasing. However, the sluggish kinetics of the oxygen evolution reaction (OER) hinders the practical application and widespread use of water-splitting technologies; therefore, to address this challenge, it is essential to develop cost-effective and efficient OER catalysts. In this work, we have synthesized an inexpensive and tunable FeCoMn Prussian blue analogue (PBAs) as an efficient OER catalyst via a straightforward process. The ratio of the Co and Mn to optimize the electrochemical performance, and as a result, the FeCo_0.41Mn_0.42 PBA catalyst demonstrated the best electrochemical performance (260/304 mV overpotential at 10/50 mA cm^-2, a low Tafel slope of 48 mV dec^-1 and a good stability of 72 h at 10 mA cm^-2). Additionally, X-ray absorption spectroscopy (XAS) measurements and density functional theory (DFT) calculations suggest that the FeCo_0.41Mn_0.42 PBA possesses the optimized electronic density distribution at the active site (Co), and the doping of Mn and Fe can not only increase the electricity conductivity but also activate the critical H₂O deprotonation step.