Self-templating construction of hollow Fe-CoxP nanospheres for oxygen evolution reaction

Rational design of catalysts with well-controlled structures and compositions has been demonstrated effective to optimize the electrochemical performance. Metal-organic frameworks (MOFs) with tunable composition, morphology as well as porous structure are desirable for constructing various functional materials acting as precursors. In this work, a facile self-templating strategy is developed to synthesize hollow Fe-CoxP nanospheres. The solid Co-glycerate nanospheres are synthesized and used as self-sacrificing templates, which are converted to Co-Fe Prussian blue analogue (PBA) via an anion-exchange process by reacting with K3[Fe(CN)6] at room temperature, and then followed by phosphorization treatment to produce the Fe-CoxP. The transformation process endows the resultant product not only the hollow nanostructure, but also Fe atoms doping into the CoxP. By taking advantages of structural and compositional benefits as well as improved conductivity, the Fe-CoxP exhibits excellent electrocatalytic activity and stability toward the oxygen evolution reaction (OER), reaching the current density of 10 mA cm−2 at an overpotential of 300 mV. The post-OER catalyst is carefully characterized and the results indicate the phase transformation of the crystalline Fe-CoxP to the amorphous FeCo (oxy)hydroxides acting as the catalytically active species. The novel self-templating strategy avoids the challenge from the removal of the template, which can possibly be employed to produce a sequence of PBA-based functional nanomaterials for applications in electrochemical energy conversion and storage.