Defect engineering of Na-induced oxygen vacancies in nickel ferrite for dual-site electrocatalytic water splitting

Abstract

Electrocatalytic materials for clean energy production have been a challenging research task in the recent years. Various materials have been engineered over the years for electrocatalytic water splitting. Adhering to this aspect, a novel electrode with a bifunctional OER mechanism was developed by incorporating Na in nickel ferrite followed by electroless NiP deposition. Fine-tuning the oxygen vacancy by introducing Na and filling the Na-induced oxygen vacancies with active phosphorus sites generated an electrode system that can participate effectively in alkaline OER. The high OER efficiency of the electrode was due to its surface functionalities and good electron conductivity, which directed the OER via a dual functional mechanism involving OVSM and AEM. The compact electrode with very fine morphology, functional components, Na-induced oxygen vacancies, phosphorus active sites and the redox couple of metals boosted the OER. As an indicator of the OER efficiency, the developed electrode exhibited an R_ct value as low as 784 ohm at an open circuit potential. Incorporation of the functional catalyst into NiP resulted in a fourfold increase in ECSA and a lower OER overpotential of 310 mV at 10 mA cm⁻². Furthermore, the stability tests and the comparative study of the OER results indicated that the systems' performance and promising electrochemical characteristics are suitable for large-scale applications. The photocatalytic hydrogen production performance under sunlight revealed that the developed plate was able to produce 1.86 mmol cm⁻² of hydrogen for 5 h and generate a high photocurrent of 11.4 mA cm⁻² at 1.54 V vs. RHE under light illumination.