MOF‐Derived Iron‐Cobalt Phosphide Nanoframe as Bifunctional Electrocatalysts for Overall Water Splitting

Abstract

Transition metal phosphides (TMPs) have emerged as an alternative to precious metals as efficient and low‐cost catalysts for water electrolysis. Elemental doping and morphology control are effective approaches to further improve the performance of TMPs. Herein, Fe‐doped CoP nanoframes (Fe‐CoP NFs) with specific open cage configuration were designed and synthesized. The unique nano‐framework structured Fe‐CoP material shows overpotentials of only 255 and 122 mV at 10 mA cm−2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, overwhelming most transition metal phosphides. For overall water splitting, the cell voltage is 1.65 V for Fe‐CoP NFs at a current density of 10 mA cm−2, much superior to what is observed for the classical nanocubic structures. Fe‐CoP NFs show no activity degradation up to 100 h which contrasts sharply with the rapidly decaying performance of noble metal catalyst reference. The superior electrocatalytic performance of Fe‐CoP NFs due to abundant accessible active sites, reduced kinetic energy barrier, and preferable *O‐containing intermediate adsorption is demonstrated through experimental observations and theoretical calculations. Our findings could provide a potential method for the preparation of multifunctional material with hollow structures and offer more hopeful prospects for obtaining efficient earth‐abundant catalysts for water splitting.