1：Experimental Design and Method Selection:

The study involves the synthesis of two–dimensional g–C3N4/α–AgAl0.4Ga0.6O2 p–n heterostructure via phase transition method under hydrothermal treatment. The methodology includes the preparation of g–C3N4 sheets and α–AgAl0.4Ga0.6O2 platelets, their coupling to form heterostructures, and characterization of their properties.

2：4Ga6O2 p–n heterostructure via phase transition method under hydrothermal treatment. The methodology includes the preparation of g–C3N4 sheets and α–AgAl4Ga6O2 platelets, their coupling to form heterostructures, and characterization of their properties. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Samples include g–C3N4, α–AgAl0.4Ga0.6O2, and their heterostructures with varying molar ratios. Data sources include XRD, SEM, TEM, FTIR, UV–vis absorption spectra, and photoelectrochemical measurements.

3：4Ga6O2, and their heterostructures with varying molar ratios. Data sources include XRD, SEM, TEM, FTIR, UV–vis absorption spectra, and photoelectrochemical measurements. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment includes PANalytical Empyrean X–ray diffractometer, Hitachi S–4800 SEM, JEM–2010 TEM, Nicolet Nexus 670 FTIR spectrometer, Hitachi U–3900 UV–vis spectrophotometer, and CHI–660E electrochemical workstation. Materials include melamine, β–AgAl0.4Ga0.6O2, and methyl orange.

4：4Ga6O2, and methyl orange. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The synthesis involves calcination of melamine to produce g–C3N4, hydrothermal treatment of β–AgAl0.4Ga0.6O2 to produce α–AgAl0.4Ga0.6O2, and coupling of g–C3N4 with α–AgAl0.4Ga0.6O2 under hydrothermal conditions to form heterostructures. Characterization and photocatalytic activity evaluation follow.

5：4Ga6O2 to produce α–AgAl4Ga6O2, and coupling of g–C3N4 with α–AgAl4Ga6O2 under hydrothermal conditions to form heterostructures. Characterization and photocatalytic activity evaluation follow. Data Analysis Methods:

5. Data Analysis Methods: Data analysis includes XRD pattern analysis, SEM and TEM imaging, FTIR spectra analysis, UV–vis absorption spectra analysis, and photoelectrochemical property evaluation.