Porous transition metal phosphides derived from Fe-based Prussian blue analogue for oxygen evolution reaction

Recently, transition metal phosphides (TMPs) have been reported as a new kind of anode catalyst for oxygen evolution reaction (OER), and the composition of the material largely determines the performance of the catalysts. However, few reports explore how electrocatalytic performance of TMPs changed with the composition of the catalysts. We selected three different component Fe-based Prussian blue analogues (PBA) as precursors and transformed them into corresponding metal phosphides by simple heat treatment. By tuning the phosphidation temperature, a series of FeCoP, FeNiP, and FeMnP were obtained, in which FeCoP under a suitable phosphidation temperature at 400 °C exhibits most obviously porous structure and broadest distribution of pore size, which benefits for the mass transfer and oxygen release during OER. Besides, the charge-transfer resistance (Rct) of TMPs has greatly decreased by introducing of Co in comparison of Ni and Mn, which accelerate the electron transport in OER. Due to the porous geometric structure and unique electronic structure, FeCoP-400 shows excellent and stable electrocatalytic activities of OER in 1 M KOH, with overpotentials of 261 mV at a current density of 10 mA cm−2, superior to commercial RuO2 and most OER electrocatalysts. Furthermore, FeCoP-400 exhibits outstanding stability with only 4% increase in potential during 24 h chronopotentiometry.