Acid-etched defective NiCoFe layered double hydroxides for enhanced oxygen evolution reaction

Abstract

Layered double hydroxides (LDHs) have emerged as promising low-cost electrocatalysts for the oxygen evolution reaction (OER) in recent years. However, their widespread application is limited by the scarcity of intrinsic active sites. Herein, defect-rich NiCoFe–LDHs were synthesized using hydrochloric acid (HCl) etching and nitric acid (HNO₃) etching. The HCl-etched NiCoFe–LDH (HCl–NiCoFe–E2) and HNO₃-etched NiCoFe–LDH (HNO₃–NiCoFe–E2) exhibited OER overpotentials of 291 mV and 312 mV at 50 mA cm⁻², with corresponding Tafel slopes of 42 mV dec⁻¹ and 62 mV dec⁻¹, respectively, outperforming the pristine NiCoFe–LDH and commercial RuO₂ in OER performance. Material characterization showed that the enhanced electrocatalytic activity of acid-treated NiCoFe–LDHs primarily results from their abundant oxygen vacancies, metal vacancies and thinner nanosheets. The OER activity of HCl–NiCoFe–E2 is higher than that of HNO₃–NiCoFe–E2, attributed to the exchange of chloride ions for interlayer nitrate ions in NiCoFe–LDH, thereby facilitating the acid etching reaction. This work presents a facile and cost-effective strategy to optimize the OER performance of LDHs.