1：Experimental Design and Method Selection:

The study involved synthesizing hierarchical WO3 hollow microspheres via a modified solvothermal method and loading Au nanoparticles using a wet impregnation method. The rationale was to enhance gas sensing performance through structural and catalytic modifications. Theoretical models included depletion theory for gas sensing mechanisms and electronic sensitization effects of noble metals.

2：Sample Selection and Data Sources:

Samples included pristine WO3 and Au-loaded WO3 with nominal Au contents of 0.5, 1, 1.5, 1.8, 2.0, and 2.5 wt%, labeled as G1 to G6. Materials were synthesized using tungsten hexachloride (WCl6) and chloroauric acid tetrahydrate (HAuCl4·4H2O) as precursors. Data sources included characterization techniques and gas sensing measurements.

3：5, 1, 5, 8, 0, and 5 wt%, labeled as G1 to GMaterials were synthesized using tungsten hexachloride (WCl6) and chloroauric acid tetrahydrate (HAuCl4·4H2O) as precursors. Data sources included characterization techniques and gas sensing measurements. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included X-ray diffractometer (XRD, PANalytical X’pert PRO), BET surface area analyzer (TriStar II 3020), FESEM (Sigma 500), TEM (FEI Tecnai G2 F20), XPS (Perkin Elmer PHI 5300), ICP-AES, electrochemical workstation (CHI660E), and gas sensor test system (WS-30A). Materials included WCl6, HAuCl4·4H2O, acetic acid, ethanol, and double distilled water.

4：Experimental Procedures and Operational Workflow:

Synthesis involved solvothermal treatment of WCl6 in acetic acid at 180°C for 12 h, followed by calcination at 500°C for 2 h to obtain WO3. Au loading was done by adding HAuCl4 solution to WO3 suspension in ethanol, stirring, centrifuging, drying, and calcining at 300°C for 1 h. Characterization included XRD, BET, SEM, TEM, XPS, ICP-AES, EIS, and Mott-Schottky analysis. Gas sensing tests were performed using a WS-30A system, coating samples on alumina tubes, and measuring responses to various gases at controlled temperatures.

5：Au loading was done by adding HAuCl4 solution to WO3 suspension in ethanol, stirring, centrifuging, drying, and calcining at 300°C for 1 h. Characterization included XRD, BET, SEM, TEM, XPS, ICP-AES, EIS, and Mott-Schottky analysis. Gas sensing tests were performed using a WS-30A system, coating samples on alumina tubes, and measuring responses to various gases at controlled temperatures. Data Analysis Methods:

5. Data Analysis Methods: Data analysis involved indexing XRD patterns to standard PDF cards, calculating BET surface areas, analyzing XPS spectra for elemental states, and evaluating gas sensor responses (Ra/Rg for reducing gases). Statistical analysis included linear fitting of response vs. concentration data and stability assessments over time.