1：Experimental Design and Method Selection:

The study aimed to synthesize a composite photocatalyst with Lewis acid sites and plasmonic properties. A Ni-modified low-crystalline Ni-Ge hydroxide was synthesized via an ion exchange reaction between Ni(NO3)2 and Na2GeO3 in sodium borohydride solution at 273 K. The methodology included characterization techniques to analyze structure, morphology, and optical properties, and photocatalytic tests to evaluate CO2 reduction performance under different light irradiations.

2：Sample Selection and Data Sources:

Samples included Ni/Ni3Ge2O5(OH)4 and Ni3Ge2O5(OH)4 for comparison. Data were sourced from synthesized materials and standard references (e.g., JCPDS for XRD).

3：List of Experimental Equipment and Materials:

Equipment included XRD (Rigaku Ultima III), SEM (FEI Nova Nano SEM 230), TEM (FEI Tecnai G2 F30 S-Twin), UV-vis spectrophotometer (UV-LAMBDA 950, PerkinElmer), FT-IR spectrometer (Nicolet Nexus 870), XPS (PHI5000 Versa Probe), BET surface area analyzer (Micromeritics Tristar-3000), electrochemical workstation (CHI Instruments CHI760E), gas chromatographs (GC-8A and GC-2014, Shimadzu), and a 300 W Xe lamp. Materials included Na2GeO3, GeO2, Na2CO3, NaBH4, Ni(NO3)2, deionized water, and high-purity CO

4：Experimental Procedures and Operational Workflow:

Synthesis involved preparing Na2GeO3, then reacting with Ni(NO3)2 in NaBH4 solution at 273 K with stirring, followed by centrifugation, washing, and freeze-drying. Characterization included XRD, SEM, TEM, UV-vis DRS, FT-IR, XPS, BET, and electrochemical measurements. Photocatalytic tests were conducted in a glass reactor with catalyst dispersion, CO2 introduction, water injection, dark equilibrium, and irradiation with gas sampling for GC analysis.

5：Data Analysis Methods:

Data were analyzed using XPS peak area calculations, BET method for surface area, Kubelka-Munk transformation for absorption spectra, and GC for product quantification. Statistical analysis involved comparing yields and rates between samples.