Continuously Porous Hybrid Conducting Polymers for Electrochemical Water Splitting

Abstract

The development of efficient and cost-effective electrocatalysts for water splitting is essential for sustainable hydrogen production and the transition toward renewable energy systems. However, noble metal-based catalysts, such as platinum and iridium, which are considered benchmark materials in this field, limit large-scale hydrogen production due to their high cost and scarcity. In this work, potential alternatives in the form of polypyrrole (PPy)-based composite electrocatalysts incorporating transition metal sulfides (MoS2 and CoS2) were developed and systematically investigated. The composites were synthesized using a biphasic microemulsion (BME) polymerization approach, which enables the formation of a continuously porous and interconnected polymer network with uniformly dispersed catalytic phases. The resulting PPy-MoS2-CoS2/C composites were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), confirming the formation of a hierarchical structure with well-distributed active components. Electrochemical performance toward the hydrogen evolution reaction (HER) was evaluated in acidic media using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry, and gas chromatography (GC). The results demonstrate that both catalyst loading and film thickness strongly influence electrocatalytic activity, with optimal performance achieved at 3 wt% sulfide loading and a film thickness of 200 μm. Under these conditions, the ternary PPy-MoS2-CoS2/C composite exhibited a low overpotential of approximately 50 mV at -10 mA cm-2. Comparative analysis revealed that the incorporation of PPy enables a significant reduction in catalyst loading without compromising performance. Furthermore, the ternary composite outperformed binary systems, demonstrating a clear synergistic effect between MoS2, CoS2, and the conductive polymer matrix. Overall, this study highlights the importance of composite architecture and synthesis strategy in designing efficient electrocatalysts and demonstrates that the BME approach represents a promising route for the development of high-performance, low-cost materials for hydrogen production via water electrolysis.