Electrochemical Reconstruction of Layered FeNi Metal−Organic Framework Nanostructures for Simulated Seawater and Alkaline Water Oxidation

Abstract

Electrocatalytic water splitting for hydrogen production is an important approach to facilitate the transition toward a low-carbon energy system. Great efforts have been devoted to developing highly active and durable non-precious-metal catalysts. Herein, a layered iron-nickel bimetallic metal−organic framework (FeNi-MOF) with a nanoscale single-layer thickness of approximately 50 nm was fabricated via a room-temperature component regulation strategy. This nanoscale layered structure provides abundant surface active sites and efficient electron transport pathways. The as-prepared catalyst exhibits outstanding oxygen evolution reaction (OER) performance, delivering an overpotential of only 242 mV at a current density of 10 mA cm−2, and possesses excellent corrosion resistance in simulated seawater electrolytes. Assembled with commercial Pt/C to construct a full water-splitting electrolyzer, the system achieves a current density of 10 mA cm−2 at a cell voltage of 1.56 V and maintains stable operation for 24 h. Mechanistic investigations verify that FeNi-MOF undergoes dynamic surface reconstruction during the OER process to form highly active FeNiOOH as the real catalytic active phase. Density functional theory calculations reveal that the electronic synergy between Fe and Ni sites optimizes the adsorption free energy of oxygen-containing intermediates, reducing the thermodynamic energy barrier of the rate-determining step from 1.52 eV to 1.39 eV and thus greatly enhancing the intrinsic catalytic activity. This work clarifies the reconstruction mechanism of MOF-based precatalysts and provides a promising strategy for designing high-efficiency non-precious metal electrocatalysts for freshwater and seawater electrolysis.