A hybrid GaN/GaO structure anchored on carbon cloth as a high-performance electrode of supercapacitors.

A hybrid structure of GaN/GaO microrods was fabricated on carbon cloth (CC) using a hydrothermal process combined with a high-temperature nitridation followed by an air annealing process. By elevating the post-annealing temperature to 500 °C, both electron density () and specific capacitance () of the composite electrode were significantly enhanced. Symmetric SCs assembled with GaN/CC-500 showed great potential in both 1 M HSO aqueous solution and a PVA-HSO gel-like electrolyte. The aqueous symmetric GaN/CC-500 SC exhibited an excellent capacitance (1301.20 mF cm, 0.5 mA cm), high rate capability (75.23% of capacitance retention at 10 mA cm), outstanding cycling stability (77.27% of capacitance retention after 20 000 cycles, 10 mA cm), and large energy storage capability (27.53 μW h cm of energy density, 0.10 mW cm of power density). All-solid-state symmetric GaN/CC-500 SC also manifested a high capacitance (1183.35 mF cm, 0.5 mA cm) and good rate capability (53.98% capacitance retention, 10 mA cm). The high electrochemical performance of the GaN/CC-500 electrode is attributed to the GaN/GaO hybrid structure, with α-GaO providing absorption/redox active sites on the surface, and the heavily oxygen-doped GaN enabling fast electron transport. The microrods with the GaN/GaO hybrid structure as the active material for solid SCs can deliver an energy density of 0.58 W h kg (3.54 mW h cm) with a power density of 154 W kg (0.94 W cm). The mechanism identified in this work would be helpful in designing GaN-based energy storage devices with better performances in the future.