Anodic oxidation-accelerated self-reconstruction of tri-metallic Prussian blue analogue toward robust oxygen evolution reaction performance

Developing a low-cost and highly efficient oxygen evolution reaction (OER) electrocatalyst and understanding the underlying reaction mechanism are critical for sustainable renewable energy conversion and storage. Here, we use a facile and low-energy co-precipitation method to synthesize tri-metallic Prussian blue analogue (PBA) of FeCoNi-PBA. The FeCoNi-PBA exhibits promising catalytic performance in alkaline media, showing a low overpotential of 236 mV at 10 mA cm⁻², small Tafel slope of 43.8 mV dec⁻¹, and excellent long-term durability at 100 and 400 mA cm⁻². We show that the FeCoNi-PBA is etched by the high-pH 1 M KOH electrolyte, and the anodic applied potential during electrolysis accelerates the formation of metal (oxy)hydroxide. In-situ Raman and post-mortem characterizations reveal that the applied anodic potential promotes the phase transformation to complete the reconstruction of PBA to metal (oxy)hydroxide embedded in a carbon matrix with fully exposed active sites. The metal (oxy)hydroxide serves as the real active sites while the carbon matrix with high conductivity and hydrophilicity facilitates the electron transfer and electrolyte diffusion.