Covalent Integration of Siloxene and graphene derivatives into 2D Heterostructures as metal-free catalysts for the oxygen evolution reaction

• Novel covalent siloxene-graphene 2D/2D heterostructures. • FG-fSN shows superior OER activity (370 mV at 10 mA cm⁻²). • Enhanced charge transfer and active surface area achieved. • Heterostructures demonstrate excellent electrochemical stability. While physically stacked 2D heterostructures offer synergistic properties, their reliance on weak van der Waals interactions often limits long-term stability. In contrast, covalently bonded 2D heterostructures provide durable interfaces and precisely controlled interlayer spacing, unlocking more effective synergistic effects. Herein, we report the synthesis of robust 2D/2D hybrids by covalently linking amine-functionalized siloxene nanosheets (fSN) with fluorographene (FG) via nucleophilic substitution and with graphene acid (GA) via carbodiimide-mediated amide coupling. Structural and spectroscopic analyses confirmed the formation of stable C–N and amide linkages, alongside the preservation of the constituent 2D architectures. As metal-free oxygen evolution reaction (OER) catalysts in alkaline media, FG–fSN achieves an overpotential of 370 mV at 10 mA cm⁻², outperforming the individual components due to accelerated charge transfer, increased electrochemically active surface area, and enhanced stability. GA–fSN also demonstrates improved OER activity and durability, though to a lesser extent, underscoring the critical role of interfacial chemistry. These results establish covalent siloxene–graphene derivative heterostructures as a versatile and high-performance platform for durable metal-free electrocatalysts, offering a promising route for next-generation energy conversion technologies. Robust covalent 2D heterostructures were formed by linking amine-functionalized siloxene with fluorographene and graphene acid, producing stable C–N and amide bonds while preserving 2D architectures. The hybrids show enhanced OER activity in alkaline media, faster charge transfer, larger electrochemical surface area, and >94 % durability over 24 h, establishing versatile metal-free electrocatalysts for energy applications.