Structural, morphological, optical, and electrochemical studies of α-Bi2O3 and CuBi2O4 photocathode materials

Herein, we synthesized tetragonal CuBi2O4 powder from raw Bi2O3 and CuO powders by the combination of hand-milling and ball-milling and subsequent sintering at 750 degrees C for 4 h in air. The structural, morphological, optical, and physicochemical properties of Bi2O3 and CuBi2O4 powder samples were examined by a variety of characterization tools including X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM), UV-Vis-NIR spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical workstation. The combined XRD and Raman data analyses confirmed the monoclinic (P2(1)/c) and tetragonal (P4/ncc) phases of alpha-Bi2O3 and CuBi2O4, respectively. The average crystallite domain size was estimated to be similar to 72 nm for alpha-Bi2O3 and similar to 50 nm for CuBi2O4. SEM micrographs exhibit microrod-like morphologies for alpha-Bi2O3 and spherical nanograin-like morphologies for CuBi2O4. XPS studies revealed the Bi 4f peak split into Bi 4f(5/2) and Bi 4f(7/2) and the presence of Bi3+ valence states for both alpha-Bi2O3 and CuBi2O4, whereas Cu2+ valence state for CuBi2O4. The optical bandgap was estimated from diffuse reflection data and found to be similar to 2.62 and similar to 1.77 eV for alpha-Bi2O3 and CuBi2O4, respectively. Finally, Cyclic Voltammetry and (Photo)Electrochemical Impedance studies of alpha-Bi2O3 and CuBi2O4 slurries atop the screen-printed gold electrode with aqueous Na2SO4 electrolyte were conducted and compared to demonstrate a quick assessment technique of their photocatalytic performance.