NiFe2O4 nanoflowers with Mo doping for self-powered hydrogen production at large current density

Abstract

A lot of exploration has been carried out in recent years on catalysts applied for water splitting or for rechargeable zinc–air batteries, but research into catalysts that can serve both remains rare. Hence, developing an excellent catalyst that can be applied for self-powered hydrogen production, combining an electrocatalytic water splitting device with a rechargeable zinc–air battery, remains a challenge. Herein, we introduced Mo directly into iron foam (IF)-supported NiFe₂O₄ and synthesized an in situ-doped nanoflower-like material. The Mo–NiFe₂O₄/IF so formed can deliver a large current density (>1000 mA cm⁻²) during the course of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Moreover, when the output current density is 10 mA cm⁻², it requires a lower cell voltage (1.69 V) than undoped NiFe₂O₄/IF (1.72 V). In addition, when the obtained Mo–NiFe₂O₄/IF acts as an air-cathode of a zinc–air battery, the corresponding assembled battery can maintain long-term (>700 h) cycling stability, with a much narrower voltage gap (0.72 V) than a battery assembled with undoped NiFe₂O₄/IF (0.81 V) at a current density of 10 mA cm⁻². Moreover, the water splitting device can operate efficiently when applied to Mo–NiFe₂O₄/IF-based batteries as a power supply. Therefore, we obtained an outstanding self-powered hydrogen production catalyst, and we believe this work will thereby provide a wide application guidance for other excellent OER/HER materials.