Graphene is an attractive soft material for various applications due to its unique and exclusive properties. The processing and preservation of 2D graphene at large scales is challenging due to its inherent propensity for layer restacking. Three-dimensional graphene-based nanomaterials (3D-GNMs) preserve their structures while improving processability along with providing enhanced characteristics, which exhibit some notable advantages over 2D graphene. This feature article presents recent trends in the fabrication and characterization of 3D-GNMs toward the study of their morphologies, structures, functional groups, and chemical compositions using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Owing to the attractive properties of 3D-GNMs, which include high surface areas, porous structures, improved electrical conductivity, high mechanical strength, and robust structures, they have generated tremendous interest for various applications such as energy storage, sensors, and energy conversion. This article summarizes the most recent advances in electrochemical applications of 3D-GNMs, pertaining to energy storage, where they can serve as supercapacitor electrode materials and energy conversion as oxygen reduction reaction catalysts, along with an outlook.

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A novel electrocatalyst with high activity and enhanced durability toward the hydrogen evolution reaction (HER) in alkaline media has been designed and fabricated based on sodium hexa-titanate (Na2Ti6O13) nanowires synthesized by a hydrothermal process and modified with Co­(OH)2 quantum dots (QDs) by a facile chemical bath deposition (CBD) method. The current response of the developed Ti/Na2Ti6O13/Co­(OH)2 nanocomposite electrode attained 10 mA cm–2 at an overpotential of 159 mV. The nanocomposite electrode exhibited a high stability at an applied current of 100 mA cm–2. The remarkable catalytic behavior was achieved with a loading amount of ca. 0.06 mg cm–2 cobalt hydroxide. This is attributed to the high electrochemically active surface area (EASA) gained by the nanowire-structured substrate and considerable enhancement of electrochemical conductivity with the use of Co­(OH)2 quantum dots as an active material. The superior catalytic activity and high stability show that the developed catalyst is a promising candidate for hydrogen production in alkaline media.

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Three-dimensional (3D) graphene-based materials are highly desirable for supercapacitor applications; however, their synthesis requires multiple time-consuming steps that involve templates and cross-linkers. Thus, chemically derived graphene through the reduction of graphene oxide is preferred for scalable synthesis. Here, a facile one-pot wet chemical synthesis for an improved highly interconnected 3D reduced graphene oxide (3D-rGO) was developed where the extent of oxidation and the temperature for reduction were optimized. These facile interconnected structures were achieved through covalent linkages via functional groups. The optimized 3D-rGO demonstrated a high C/O ratio (5.2) and nominal defect density (I D/I G = 0.90) due to its stable structure. Electrochemical characterization revealed that the 3D-rGO possessed a superior specific capacitance of 256 F g–1 in an aqueous electrolyte. Trasatti analysis revealed an 84% contribution from the electrical double-layer (EDL) mechanism, which implied a high sp2 carbon content and superior conductivity. This superb performance, which was further validated in a quasi-solid-state device in an aqueous gel electrolyte (H2SO4-PVA), revealing that an excellent gravimetric energy density of 24.4 Wh kg–1 could be delivered at a power density of 1 kW kg–1. A maximum power density of 28 kW kg–1 delivered a stable 18.8 Wh kg–1 of energy. Furthermore, the supercapacitor exhibited 184 F g–1, with a capacity retention of 91% following 10,000 cycles at 10 A g–1, which is promising for practical energy storage applications.