Amorphous FeOOH nanoparticles decorated on defect-rich porous Ni MOF nanosheet based hierarchical architectures toward superior OER performance

Abstract

Although metal–organic frameworks (MOFs) with unique characteristics such as a large surface area, high designability as well as a diversity of structures have been demonstrated as promising materials for highly efficient electrocatalysts toward the oxygen evolution reaction (OER), their performance still cannot meet the industrial requirements. Herein, amorphous FeOOH nanoparticles decorated on defect-rich porous Ni MOF nanosheet based hierarchical architectures were constructed via a simple electrodeposition route and their corresponding potential for the OER was explored. In detail, the defect-rich porous Ni MOF nanosheets were firstly synthesized by a hydrothermal route, followed by alkali etching treatment. After subsequent electrodeposition, amorphous FeOOH nanoparticles were uniformly loaded on the surface of the MOF nanosheets. The as-prepared hierarchical nanocomposite exhibited improved conductivity, a larger electrochemical surface area and promoted oxidation processes for the transformation of Ni²⁺ to Ni³⁺ and Ni³⁺ to Ni^>3+ in the presence of FeOOH. As a result, the hierarchical nanocomposite required only 267 mV for the OER to reach a catalytic current density of 20 mA cm⁻² in 1.0 M KOH. It also showed a small Tafel slope of 79 mV dec⁻¹ and remarkable stability. What is more, the hierarchical nanocomposite possessed higher OER performance, lower Tafel slopes and smaller charge transfer resistance than each individual component as an electrocatalyst, showing a synergistic effect of the defect-rich porous Ni MOF and amorphous FeOOH nanoparticles. In brief, this work provided a feasible strategy for further exploring the application potential of MOF-based hierarchical composites for an efficient electrocatalytic OER.