Nanodiamond Covalently Anchored Reduced Graphene Oxide 3D Ultraelastic Aerogels toward 2.0 V Aqueous Supercapacitors

Conventional aqueous symmetric carbon-based supercapacitors face intrinsic voltage limitations (typically ≤ 1.0 V), fundamentally constraining their energy density potential. In this work, oxygen-functionalized detonation nanodiamonds (ONDs) and graphene oxide (GO) are self-assembled into three-dimensional (3D) rGO-OND ultraelastic aerogels through sp3–sp2 carbon hybridization. This hierarchical 3D architecture establishes dual-conductive pathways for electrons and phonons while maintaining exceptional mechanical resilience. The optimized rGO-10%OND composite demonstrates groundbreaking electrochemical performance in symmetric supercapacitor configurations. The optimized rGO-10%OND, as electrode materials in the aqueous symmetric supercapacitor device, can stably operate for charging and discharging within an unprecedented voltage window of 0–2.0 V, surpassing conventional limits by 100%. Meanwhile, the Coulombic efficiency and capacitance retention are both close to 100% after 10000 cycles. It achieved an energy density of 23.1 Wh kg–1 at a power density of 1000 W kg–1. In situ scanning electrochemical microscopy (SECM) and in situ Raman spectroscopy demonstrate that the excellent electrochemical performance is mainly attributed to exceptional redox reactivity, accelerated ion diffusion kinetics, and remarkable structural integrity of rGO-10%OND.