1：Experimental Design and Method Selection:

The study involves synthesizing g-C3N4 from DES precursors (urea and ammonium thiocyanate mixtures) via thermal polymerization at 550°C for 2 hours, comparing with conventional precursors (melamine, urea, AT). Methods include XRD, FTIR, XPS, UV-Vis DRS, PL spectroscopy, TEM, SEM, BET surface area analysis, TGA, and photocatalytic activity tests for RhB degradation and hydrogen evolution.

2：Sample Selection and Data Sources:

Samples include CNU (from urea), CNAT (from AT), CN2U1AT (from DES with urea:AT mass ratio 2:1), CN1U2AT (from DES with urea:AT mass ratio 1:2), and pristine g-C3N4 (from melamine). Data are obtained from laboratory experiments and characterization techniques.

3：List of Experimental Equipment and Materials:

Equipment includes X'Pert Pro powder diffractometer (XRD), Micromeritics ASAP 3020 (BET), Zeiss SIGMA (SEM), JEM-1400 and FEI Tecnai 30 (TEM/HRTEM), TG 209F1 (TGA), Thermo Nicolet Nexus spectrometer (FTIR), Qtac100 spectrometer (XPS), Varian-Cary 5000 (UV-Vis DRS), Hitachi F-7000 (PL), FLS980 fluorescence lifetime spectrophotometer (time-resolved PL), JEM-F200 with Gatan Enfina Spectrometer (EELS), CHI-660E electrochemical system (photocurrent), Shimadzu UV-2550 (UV-vis spectrophotometer), gas chromatography with TCD (hydrogen evolution). Materials include urea, ammonium thiocyanate, melamine, ethanol, triethanolamine, methanol, benzoquinone, P25 TiO2, chloroplatinic acid, Nafion solution, DI water.

4：Experimental Procedures and Operational Workflow:

Precursors are calcined at 550°C for 2 hours. DESs are prepared by grinding urea and AT mixtures. Characterization involves standard procedures for each technique. Photocatalytic tests involve RhB degradation under visible light with scavengers and hydrogen evolution with Pt cocatalyst and TEOA scavenger.

5：Data Analysis Methods:

Data are analyzed using Kubelka-Munk function for bandgaps, Langmuir-Hinshelwood model for kinetics, and fitting equations for PL lifetimes. Statistical analysis includes comparison of rates and constants.