1：Experimental Design and Method Selection:

The study employed an ultrasonic-assisted calcination method to synthesize the ternary heterojunction photocatalyst. The design rationale was to integrate 2D Ti3C2 MXene and g-C3N4 to form heterojunctions that enhance charge separation and photocatalytic efficiency. Theoretical models included n–n heterojunction and n-type Schottky heterojunction mechanisms to explain electron transfer.

2：Sample Selection and Data Sources:

Raw materials included Ti3AlC2 powder (≥98% purity) for Ti3C2 synthesis and melamine for g-C3N4 production. Pollutants used were aniline and rhodamine B (RhB) for degradation tests. Data sources were experimental measurements from characterization techniques.

3：List of Experimental Equipment and Materials:

Equipment: SEM (Hitachi S4800 and JSM-6510LV), TEM (FET Tecnai G2 F20), XRD (Bruker D8 Advance), FTIR (Nicolet Nexus 670), XPS (Thermo ESCALAB 250), UV–Vis DRS (TU-1901, PGeneral), PL spectrophotometer (Hitachi F-7000), TOC analyzer (Multi N/C 3100, Analytik Jena AG), surface area analyzer (Micromeritics ASAP 2020), gas chromatography (Varian with Elite-5MS and DB-35MS columns), electrochemical workstation (CHI 660D), tube furnace (CY-O 1200-R80IL), Xe lamp (300-W). Materials: Ti3AlC2 powder (Beijing Forsman Technology Co., Ltd.), HF solutions (49 wt%, Sinopharm Chemical Reagent Co. Ltd), melamine (Sinopharm Chemical Reagent Co. Ltd), ethanol, deionized water (SW AC-520), Na2SO4, Nafion, indium–tin oxide glass, aniline, RhB.

4：Experimental Procedures and Operational Workflow:

Ti3C2 was exfoliated from Ti3AlC2 using HF etching, washed, and dried. g-C3N4 was synthesized by calcining melamine. TiO2@Ti3C2/g-C3N4 composites were prepared by ultrasonicating mixtures of Ti3C2 and g-C3N4 in ethanol, followed by drying and calcination at 200°C. Characterization involved SEM, TEM, XRD, FTIR, XPS, UV–Vis DRS, PL, BET, TOC, and electrochemical measurements. Photocatalytic tests used a Xe lamp with cutoff filters, with samples stirred in pollutant solutions, and absorbance measured over time.

5：Data Analysis Methods:

Data analysis included XRD pattern indexing, FTIR peak assignment, XPS curve fitting, BET surface area calculation, Kubelka–Munk function for bandgap determination, PL intensity comparison, photocurrent and EIS analysis for charge carrier behavior, and kinetic plots for degradation rates.