1：Experimental Design and Method Selection:

The study employed a facile in-situ synthesis method using l-arginine to synthesize CeO2 nanoparticles on exfoliated g-C3N4 nanosheets, aiming to achieve nitrogen doping and uniform distribution without complex equipment.

2：Sample Selection and Data Sources:

Bulk g-C3N4 was synthesized from melamine, exfoliated via thermal oxidation, and composites were prepared with CeCl3·7H2O and l-arginine in ethanol.

3：List of Experimental Equipment and Materials:

Materials included melamine (Sigma-Aldrich, 99% AR), CeCl3·7H2O, l-arginine, ethanol; equipment included muffle furnace, ultrasonicator, magnetic stirrer, hot air oven, centrifuge, XRD (Bruker D8 advance eco diffractometer), XPS (Thermo Scientific K-Alpha spectrometer), HR-TEM (JEOL JEM 2100), BET (Micromeritics TriStar II), UV-Vis (Varian CARY 300), SEM (JEOL JSM-IT 500), and solar simulator (suntest CPS+).

4：Experimental Procedures and Operational Workflow:

Steps involved synthesis of bulk g-C3N4 by heating melamine at 550°C for 2h, exfoliation at 550°C for 3h, composite synthesis by dispersing exfoliated g-C3N4 in ethanol with l-arginine and CeCl3·7H2O, stirring, heating at 70°C overnight, centrifugation, washing, and drying. Characterization techniques were applied, and photocatalytic tests used a xenon lamp with diuron solution, sampling every 20min for UV-Vis analysis.

5：Data Analysis Methods:

Bandgap calculated using Tauc plot from UV-Vis spectra, surface area via BET method, pore size via BJH method, kinetic analysis using Langmuir-Hinshelwood pseudo-first-order equation, and XPS deconvolution for chemical states.