Construction of an amorphous Fe-doped CoOOH coated crystalline Co2Mo3O8 heterostructure for stable and efficient oxygen evolution

Abstract

Hydrogen energy is vital for decarbonization, with renewable-powered electrolysis key to green hydrogen production. However, the OER anode reaction suffers from sluggish kinetics (four-electron transfer), requiring high overpotentials that reduce system efficiency and cost-effectiveness. Research therefore focuses on developing high-performance, low-cost OER electrodes to replace noble-metal catalysts and overcome stability limitations of nickel-based electrodes. In this work, an amorphous/crystalline heterostructure composed of amorphous Fe-doped CoOOH and Co₂Mo₃O₈ was prepared through hydrothermal synthesis, calcination, interfacial engineering, and electrochemical reconstruction. The heterostructure exhibits a unique structure characterized by an interwoven arrangement of amorphous and crystalline phases. Electrochemical analysis shows that the introduction of Fe ions effectively promotes the OER activity, and significantly accelerates the intrinsic OER kinetics. Structural characterization and DFT calculations reveal that Fe incorporation in CoOOH and the formation of an amorphous/crystalline heterojunction synergistically tailor the electronic configuration, leading to favorable OH⁻ binding energetics and a lowered rate-determining step (RDS) barrier for enhanced OER kinetics. Moreover, a significant enhancement in local charge density is observed at the crystalline/amorphous heterojunction interface, indicating robust interfacial electronic interactions that facilitate efficient charge transfer between the two phases. As anticipated, the heterostructure catalyst (with nickel foam as the anode substrate) exhibits exceptional OER performance (η₁₀ = 220 mV; Tafel slope = 32 mV dec⁻¹). Notably, the catalyst exhibits remarkable durability, maintaining stable operation for 280 hours at 250 mA cm⁻² without significant degradation, and in alkaline seawater. This work establishes a new paradigm for constructing high-efficiency heterointerface catalysts, significantly advancing the practical implementation of green hydrogen technologies.