Nanodiamond-integrated graphene electrodes for high-performance electrochemical supercapacitors

The advancement of energy storage technologies hinges on the development of sustainable nanostructured materials, yet challenges related to synthesis, optimization, and reproducibility persist. Graphene-based electrodes offer high electrochemical performance but suffer from rapid degradation, limiting their long-term applicability. To overcome this, a hybrid electrode composed of diamond nanoparticles (D) embedded within nano-hair structured graphene (nG), synthesized via a scalable two-step process, is introduced. The direct laser-induced integration of sp³ carbon into sp² graphene generates sp² grain boundaries in diamond, significantly enhancing conductivity, stability, and charge transport dynamics. This structural modification increases material disorder, reduces charge-transfer resistance, and boosts electrochemical performance. The D-nG hybrid achieves a remarkable specific capacitance of 7.21 mF cm⁻² at 1.53 mA cm⁻², maintaining 98 % capacity retention over 10,000 charge-discharge cycles. The hybrid electrode delivers an energy density of 2.89 mWh cm⁻² at a power density of 0.18 mW cm⁻² for a 0.5 mm diameter electrode. Furthermore, a 1 cm² symmetric pouch cell exhibits a maximum energy density of 1.09 mWh cm⁻² and a power density of 0.12 mW cm⁻², with a specific capacitance of 1.97 mF cm⁻² at 0.3 mA cm⁻². The synergistic combination of nanostructured graphene and chemically stable diamond establishes D-nG as a robust, high-performance material for next-generation electrochemical energy storage applications.