Effect of point defects on electrochemical performances of α-Ga₂O₃ microrods prepared with hydrothermal process for supercapacitor application

α-Ga₂O₃ microrods was deposited on carbon cloth (CC) using a hydrothermal process followed by a high-temperature annealing in air. The microstructure of the obtained Ga₂O₃/CC composite electrodes were characterized with scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Their electrochemical performances were tested with electrochemical impedance spectroscopy (EIS), Mott-Schottky (MS), cyclic voltammetry (CV) and galvanostatic charge/discharge techniques (GCD). By comparing the electron densities and mobilities of the Ga₂O₃/CC electrodes prepared with different hydrothermal durations, the doping mechanisms of point defects in α-Ga₂O₃ were revealed. The point defects in α-Ga₂O₃ including Ga-oxygen vacancies (Ga-V_O), gallium vacancies (V_Ga), and V_Ga-V_O complexes were all identified as the scattering centers. By extending the hydrothermal duration to more than 6 h, the electronic conductivity of the Ga₂O₃/CC electrode was enhanced by reducing the number of point defects in α-Ga₂O₃. The Ga₂O₃/CC-6h aqueous symmetrical supercapacitor (SC) showed a remarkable increase in the electrochemical performance by exhibiting a specific areal capacitance of 1394 mF cm⁻² at 0.5 mA cm⁻², with 67% of the capacitance retained when the current density was increased to 20 mA cm⁻², and 76.5% of capacitance retention after 20,000 cycles under a current density of 10 mA cm⁻². The point defect mechanism identified in the article would pave the way to develop novel energy storage devices based on α-Ga₂O₃ in the future.