Preparation of hollow CoFe Prussian blue analogues and their derived CoP-FeP nanoboxes as efficient electrocatalysts as oxygen evolution reactions

Abstract

Reasonably designing and constructing transition metal based compounds with controllable composition and structure is a promising option for obtaining economically efficient oxygen evolution reaction (OER) electrocatalysts. This paper presents a one-pot self-templated epitaxial growth, phase transition and self-dissolution strategy for constructing hollow nanoboxes/solid nanocubes of CoFe bimetallic Prussian blue analogues (PBAs). The CoFe mixed phosphide with a porous hollow nanoboxes structure obtained after subsequent phosphating heat treatment exhibite enhanced OER electrocatalytic activity in alkaline media, exhibiting a low overpotential of 230 mV and a Tafel slope of 35.5 dec⁻¹ at 10 mA cm⁻², as well as excellent stability for 48 h. The excellent OER activity of CoP-FeP nanoboxes (CoP-FeP NBs) can be attributed to the combination effect between their composition and structure. Structurally, the exquisite porous hollow nanoboxes structure greatly expands the surface area, reduces ion diffusion pathways, and reduces charge transfer resistance. Compositionally, the inner transition metal phosphide exhibits good conductivity and undergoes surface reconstruction during OER, forming high valence Co(Fe)OOH active substances in situ. The strong interface coupling effect of CoOOH/FeOOH optimizes the electronic structure. This work presents a facile and efficient strategy for the construction of PBAs hollow structural materials and the exploitation of low-cost and efficient electrocatalysts.