1：Experimental Design and Method Selection

Synthesis of SnO2 nanostructures via chemical precipitation route under optimal conditions at different pH values (3, 7 and 11).

2：Sample Selection and Data Sources

Stannous Chloride dihydrate and Potassium Hydroxide pellets were used as precursors. The samples were characterized by XRD, FESEM, TEM, PL, UV–Visible, FTIR spectroscopy and EIS measurements.

3：List of Experimental Equipment and Materials

X-ray Diffractometer (XRD; Rigaku Japan), field emission scanning electron microscope (FESEM; FEG-Quanta-450, FEI), Tecnai G220 –AI transmission electron microscope (TEM; FEI, Hillsboro, Oregon, USA), Photoluminescence spectra were observed using RF-5301PC Shimadzu spectro fluorophotometer (Japan), UV-Visible spectrum was measured via M550 Camspec UV-visible spectrophotometer, Fourier Transform Infrared (FTIR) spectra (Alpha Bruker).

4：Experimental Procedures and Operational Workflow

An aqueous solution is made by dissolving SnCl2.2H2O in DI water and 1M NaOH is added with continuous stirring. The pH of the solution is adjusted to 3, 7, and 11. The solution is stirred for 1 hour at 50 0C, set aside overnight, filtered, washed, dried at 80 0C, and annealed at 500 0C for 2 hours.

5：Data Analysis Methods

XRD analysis for crystal structure, FESEM and TEM for morphology, PL for luminescent centers, UV–Visible for optical band-gap, FTIR for vibrational and functional groups, EIS for impedance properties.