Construction of a NiFe-LDH catalyst with a three-dimensional unified gas diffusion layer structure via a facile acid etching route for the oxygen evolution reaction

Abstract

NiFe layered double hydroxide is thought to be one of the most powerful electrocatalysts for the oxygen evolution reaction (OER) due to its efficient NiFe-synergistic effects. Herein, a NiFe layered double hydroxide gas diffusion layer was in situ grown via a facile acid etching method at room temperature within 5 min. Moreover, the effect of different acids on the properties of the obtained catalysts was systematically investigated. Benefiting from the abundant oxygen vacancies, the open channel structure of flower-like morphology and three-dimensional unified structure, the as-prepared catalyst with H₂SO₄ treatment delivered 10 mA cm⁻² with an overpotential of only 275 mV and excellent stability in 1 M KOH, and exhibited outstanding performance among pristine NiFe layered double hydroxides, even superior to those of commercial Ir/Ru-based electrocatalysts. Electrochemical measurements (OH⁻ diffusion and pH dependence tests), characterization (XPS) and theoretical research revealed that the three-dimensional unified gas diffusion layer followed the lattice oxygen mechanism rather than the traditional adsorbate evolution mechanism during the OER. This work provides a highly efficient, low-cost and propagable method for the preparation of NiFe layered double hydroxide electrocatalysts which show great potential as a promising commercial catalytic material.