A secondary peak observed at around 27° in the XRD spectra is attributed to the cerium oxide (CeO₂) phase, specifically the (111) plane. This indicates the successful incorporation of cerium into the photocatalyst. Cerium is known to enhance photocatalytic performance by introducing oxygen vacancies and improving charge separation, which can extend the catalyst's activity into the visible light range. The presence of this peak provides strong evidence of cerium doping and highlights its contribution to the catalyst's structural and functional properties.