Self-standing gallium-indium-reduced graphene oxide aerogels as high-performance supercapacitor electrodes

The exploration of Group 13 (IIIA) elements, gallium (Ga) and indium (In), for energy storage remains limited despite their attractive properties. This work presents a novel, self-standing gallium indium/reduced graphene oxide aerogel (EGaInGA) synthesized via a facile, chemical-reductant-free hydrothermal method. This approach transforms liquid metal into a solid-state framework where reduced graphene oxide (rGO) sheets are integrated with gallium oxyhydroxide (GaOOH), indium hydroxide (In(OH) 3 ), and indium oxide (In 2 O 3 ) particles. When deployed as a binder-free electrode in a symmetric supercapacitor (SC), the hybrid material leverages synergistic effects. The rGO provides a conductive, porous network for electric double-layer capacitance, while the Ga/In-based compounds contribute pseudocapacitance. The device achieved a gravimetric capacitance of 99.7 F g −1 and an energy density of 27.7 Wh kg −1 at a power density of 249.3 W kg −1 in an aqueous alkaline electrolyte. Further, it retained 74% of its initial specific capacitance after 10,000 cycles with 98.4% coulombic efficiency. A multi-dimensional assessment confirmed that EGaInGA exhibited a balanced performance profiles across electrochemical, economic, and environmental criteria. This study not only demonstrates the successful integration of a liquid metal alloy into a solid, high-performance electrode but also establishes a new paradigm for harnessing Group 13 (IIIA) elements in energy storage devices.