A hybrid GaN/Ga 2 O 3 structure anchored on carbon cloth as a high-performance electrode of supercapacitors.

A hybrid structure of GaN/Ga 2 O 3 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 ( N D ) and specific capacitance ( C a ) of the composite electrode were significantly enhanced. Symmetric SCs assembled with GaN/CC-500 showed great potential in both 1 M H 2 SO 4 aqueous solution and a PVA-H 2 SO 4 gel-like electrolyte. The aqueous symmetric GaN/CC-500 SC exhibited an excellent capacitance (1301.20 mF cm -2 , 0.5 mA cm -2 ), high rate capability (75.23% of capacitance retention at 10 mA cm -2 ), outstanding cycling stability (77.27% of capacitance retention after 20 000 cycles, 10 mA cm -2 ), and large energy storage capability (27.53 μW h cm -2 of energy density, 0.10 mW cm -2 of power density). All-solid-state symmetric GaN/CC-500 SC also manifested a high capacitance (1183.35 mF cm -2 , 0.5 mA cm -2 ) and good rate capability (53.98% capacitance retention, 10 mA cm -2 ). The high electrochemical performance of the GaN/CC-500 electrode is attributed to the GaN/Ga 2 O 3 hybrid structure, with α-Ga 2 O 3 providing absorption/redox active sites on the surface, and the heavily oxygen-doped GaN enabling fast electron transport. The microrods with the GaN/Ga 2 O 3 hybrid structure as the active material for solid SCs can deliver an energy density of 0.58 W h kg -1 (3.54 mW h cm -3 ) with a power density of 154 W kg -1 (0.94 W cm -3 ). The mechanism identified in this work would be helpful in designing GaN-based energy storage devices with better performances in the future.