One-step synthesized iron foam-based NiFe2O4 applied for self-powered water splitting hydrogen production

Abstract

Rechargeable zinc–air batteries (ZABs) and electrocatalytic water splitting are two important energy conversion technologies. Although ZABs acting as a power supply to drive water splitting devices can realize self-powered hydrolysis and are of great significance, catalyst design applied for these applications remains a challenge. Herein, different from other reported NiFe₂O₄-based materials, we used iron foam (IF) as the conductive substrate, as well as the iron source to synthesize self-supported NiFe₂O₄. The achieved NiFe₂O₄/IF exhibits outstanding oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) properties compared to those of the bare IF substrate, or even the commercial RuO₂/IF and Pt/C/IF. In addition, the assembled liquid/flexible ZAB using NiFe₂O₄/IF as the air-cathode illustrates excellent electrochemical stability. After this insight and a computed theoretical data analysis, we confirm that the Ni sites acted as the most active catalytic sites during the OER process, while the Fe sites are the most active sites during the HER course. Thus, the gained NiFe₂O₄/IF is a superior candidate material applied for a self-powered water splitting device. We believe that this work will be an application extension to NiFe₂O₄-based catalysts and experimental/theoretical basis for other functional materials.