Synthesis, phase conversion and physical characteristics of mesoporous β-Ga2O3 nanostructures for catalytic applications

Abstract

Herein, α-GaOOH micro/nanorods were synthesized by facile template free hydrothermal methods. These rods were converted as mesoporous β-Ga2O3 nanostructures via thermal annealing at 900 °C for 2 h. The structural analysis (XRD) reveals the presence of orthorhombic (α-GaOOH) and monoclinic (β-Ga2O3) phases (pre- and post-annealing). The surface morphology, shape, size and porous structure, growth direction and crystalline quality of the micro/nanorods are investigated using scanning and transmission electron microscopy. Interplanar spacing of 0.37 and 0.46 nm confirms that the growth is along (2 0 1) and (−2 0 1) plane, respectively. The possible growth mechanism was proposed based on the obtained micro-graphical analyses. EDX, elemental mapping and XPS analyses revealed the existence of Ga and O and their chemical states. The characteristic Raman phonon modes confirmed the monoclinic phase of β-Ga2O3. The optical absorbance edge varies between 231 nm (GaOOH) to 290 nm (β-Ga2O3). Subsequently, the band gap varies between 5.6 and 4.4 eV. PL result showed intense ultraviolet and less intense violet-blue emissions, which can be related to the defect level emission. The BET surface area analysis confirmed the mesoporous structure with pore diameter (3.97 nm) and high specific surface area (13.87 m2/g) of Ga-3. The 98 % degradation efficiency with reaction kinetic rates of k = 0.0144/min shows a good catalytic behaviour of Ga-3 catalyst against RhB dye. The results reveal that the hydrothermally grown 1-D β-Ga2O3 mesoporous nanostructures are promising candidates for designing a catalytic and other functional nanodevices.