Bifunctional Al-Doped Fe3O4/rGO Nanocomposite Electrode for Supercapacitor and Electrocatalytic Water Splitting

This research reports the effective synthesis of magnetite (Fe3O4) nanomaterials in four different forms: undoped (F), aluminum-doped (FA), reduced graphene oxide (rGO)-anchored (FR), and Al-doped Fe3O4 coupled with rGO (FAR). A straightforward coprecipitation method was employed for the synthesis, targeting their application in water splitting and supercapacitor technologies. The synthesized nanomaterials were thoroughly examined using structural, morphological, optical (XPS), surface area (BET), and thermal characterization techniques. For the supercapacitor application, a symmetric device was fabricated by using the FAR nanocomposite, which demonstrated a specific capacitance of 128.16 F g–1 and a specific energy of 17 W h kg–1 at a current density of 1 A g–1. The device also retained approximately 79.81% of its initial capacitance and sustained a Coulombic efficiency of 80.26% up to 8000 charge–discharge cycles. In electrocatalytic assessments, the developed electrodes were tested for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The FAR nanocomposite shows an impressive performance with low overpotentials of 72 mV for HER and 287 mV for OER. Moreover, the composite achieved an overall water splitting cell voltage of 1.68 V at 10 mA/cm2 in a three-electrode setup. Stability tests via chronoamperometry confirmed the robust electrocatalytic activity of the nanocomposite for both reactions. Corrosion studies further supported the electrode’s durability, highlighting its potential for long-term sustainable operation.