Fine-controlled oxygen vacancies of nanoporous Fe doped-Ni(OH)2 composite films enabled by H2O regulated deep eutectic solvent for alkaline oxygen evolution reaction at industrial current densities

Defect engineering plays a key role in regulating intermediate kinetics of OER process. However, the controlled integration of oxygen vacancy defects into the catalyst remains a huge challenge. Herein, nanoporous Fe dopedNi(OH)2 catalyst with tunable oxygen vacancies is successfully synthesized by electrodeposition in a mixed H2O- Ethaline deep eutectic solvent. By introducing H2O in Ethaline to regulate the hydrogen bond interaction between choline chloride and ethylene glycol, the oxygen vacancies of the produced composite films can be effectively controlled. Contributing to the dual optimal design of doping and oxygen vacancy, the reinforced synergistic effect facilitates to boost the OER activity. Fe doped-Ni(OH)2 film exhibits a small Tafel slope (44 mV dec-1) and derives 100 mA cm-2 only need 370 and 210 mV in 1.0 and 6.0 M KOH, respectively. The assembled overall water splitting system delivers 100 mA cm-2 at 1.71 V and keeps smoothly at 500 mA cm- 2. A novel method is offered for tailoring the oxygen vacancy in this work, which can direct the creation of OER electrocatalysts.