The crystal structure of the metal oxides was analyzed using X-ray diffractometer (XRD, Rigaku Miniflex 600) with Co-Kɑ irradiation source (λ= 0.17902 nm). The diffractometer operated at 40 kV and 100 mA, with a step size of 0.04°, and scans were conducted over a 2θ range from 20° to 80°. The microstructure of the nanocomposites was examined by high-resolution transmission electron microscopy (HRTEM, JEM-2100Plus, JEOL) and scanning electron microscopy (SEM, Nova NanoSEM 450) integrated with energy-dispersive X-ray spectroscopy (EDX). X-ray photoelectron spectroscopy (XPS, Axis Ultra DLD spectrometer, Kratos Analytical Ltd.), which was operated at 150 W (10 mA, 15 kV) and coupled with a monochromatized Al Kα radiation (hν = 1,486.7 eV), was employed to analyze the elemental composition of the Au/BiVO4/WO3 ternary junction. The binding energy was corrected with reference to C 1s peak at 284.6 eV and the XPS spectra were processed by Casa XPS software. The surface potential mapping of nanostructures was obtained using Kelvin Probe Force Microscopy (KPFM, Dimension Icon from Bruker, Billerica, MA, USA), a non-contact atomic force microscopy (AFM) technique. The work function of the CoCr tip was calibrated by the known work function of highly oriented pyrolytic graphite as a reference. The optical property measurements were conducted by UV-Vis-NIR spectrophotometer (Lambda 1050, Perkin Elmer). The steady-state emission spectra were recorded using a RF-6000 Shimadzu Spectro Fluorophotometer at an excitation wavelength of 325 nm. The photoelectrochemical and electrochemical measurements of the developed electrodes were evaluated using an electrochemical workstation (SP-200 Potentiostat, BioLogic) equipped with EIS.