Confined heat treatment of a Prussian blue analogue for enhanced electrocatalytic oxygen evolution

Abstract

Frame-like coordination polymers (FCPs) are very promising catalyst materials because of their highly ordered structures and diversified pore surfaces. However, their poor conductivity and stability hinder their application in the field of electrocatalysis. Herein, for the first time, we try to use an FCP such as a Prussian blue analogue (PBA) directly as a catalyst candidate for the oxygen evolution reaction (OER), and report an ingenious confined heat treatment strategy to maximize its electrocatalytic performance. Our synthesized and treated NiFe^II-PBA crystals were self-grown on conducting substrates and consisted of small nanocrystals, which enabled them to facilitate electron transport and expose more active sites. As a result, the NiFe^II-PBA crystals exhibited an excellent electrocatalytic performance towards oxygen evolution in alkaline media, and an overpotential of only 285 mV is needed to achieve a current density of 50 mA cm⁻².