1：Experimental Design and Method Selection:

The study involved the preparation of KOH-modified Ni/LaTiO2N photocatalyst and its characterization using various techniques including XRD, SEM, TEM, XPS, UV-vis absorption spectra, and PL spectra. The photocatalytic CO2 reduction was tested under visible light irradiation.

2：Sample Selection and Data Sources:

LaTiO2N was prepared by nitridation of La2Ti2O7 under NH3. Ni/LaTiO2N hybrids were obtained by heating mixture of LaTiO2N and Ni(NO3)2 under NH3. KOH modification was loaded on Ni/LaTiO2N by an immersion method.

3：Ni/LaTiO2N hybrids were obtained by heating mixture of LaTiO2N and Ni(NO3)2 under NHKOH modification was loaded on Ni/LaTiO2N by an immersion method. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment used includes XRD (Rigaku Ultima III), SEM (FEI Nova Nano SEM 230), TEM (FEI Tecnai G2 F30 S-Twin), UV-vis spectrophotometer (UV-2500, Shimadzu Co.), XPS (PHI5000 Versa Probe), and PL spectra measurement system.

4：Experimental Procedures and Operational Workflow:

The photocatalytic CO2 reduction was tested in a glass reactor under visible light irradiation by a 300 W Xenon arc lamp. Gas products were analyzed by gas chromatography.

5：Data Analysis Methods:

The data were analyzed using various characterization techniques and computational calculations to understand the charge separation and CO2 reduction mechanism.