1：Experimental Design and Method Selection:

The CNPs were synthesized using a green synthesis route involving Salvia macrosiphon Boiss seeds extract as a capping agent. The synthesis process involved the reaction of cerium nitrate with the seeds extract under controlled conditions.

2：Sample Selection and Data Sources:

The seeds of Salvia macrosiphon Boiss were collected from Dargaz, Khorasan Razavi Province, Iran. The synthesis process was optimized by varying the amount of seeds extract.

3：List of Experimental Equipment and Materials:

Ce(NO3)3.6H2O was purchased from Merck (Germany). The characterization of CNPs was performed using XRD, UV-Vis and FTIR spectroscopies, FESEM, TGA, DLS, and zeta potential measurements.

4：6H2O was purchased from Merck (Germany). The characterization of CNPs was performed using XRD, UV-Vis and FTIR spectroscopies, FESEM, TGA, DLS, and zeta potential measurements. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The CNPs were synthesized by dissolving cerium nitrate in distilled water and adding it to the seeds extract solution. The mixture was heated and stirred, followed by calcination to obtain CNPs. The photo-catalytic activity was evaluated by degrading RhB dye under UV-A light irradiation.

5：Data Analysis Methods:

The photo-catalytic degradation was monitored by UV-Vis spectroscopy. The kinetic of degradation was analyzed using pseudo first-order reaction rate.