A Conjugated Polymer-Functionalized MgFe2O4 Composite Enabling Bifunctional Electrocatalysis for Overall Water Splitting

Abstract

Designing well-performing and cost-effective bifunctional electrocatalysts is essential for improving sustainable energy conversion processes involving both hydrogen evolution reaction and oxygen evolution reaction. Herein, the fabrication of conjugated polymer nanostructure-modified magnesium ferrite (MgFe2O4) nanoparticles has been reported via a facile hydrothermal method. Significantly, the MgFe2O4 (MFO)/polyaniline (PANI) nanocomposite displays excellent performance for overall water splitting, requiring low overpotentials of 739 mV@100 mA/cm2 for OER and 404 mV@100 mA/cm2 for the HER and outperforming Pt/C as a benchmarking electrocatalyst. The superior electrocatalytic performance is mainly attributed to the synergistic interaction between MFO and PANI nanosheets, which provides abundant electroactive sites and facilitates efficient electron transfer. Combining experimental results with density functional theory reveals that interfacial charge transfer in the nanocomposite optimizes hydrogen adsorption free energy (ΔGH), thereby enhancing the overall electrocatalytic activity. A photovoltaic-assisted water electrolysis system was assembled to evaluate the practical applicability of the developed nanocomposite. In alkaline media, MFO/PANI demonstrates excellent operational stability over 20 h at −0.5 V vs RHE, maintaining a nearly unchanged current density, highlighting its robust electrocatalytic performance. The present study highlights the strong potential of nanocomposites as a high-performance and durable bifunctional electrocatalyst for green hydrogen production.