I'm working on photoelectrochemical water splitting, and the material is core-shell nanoparticles with a TiO₂ shell and a ferrite core. The films of the core-shell nanoparticles were prepared using the drop-casting method. However, when I performed photocurrent measurements for the prepared films, I observed a higher photocurrent response for TiO₂ compared to core-shell nanoparticles under a halogen lamp. Why is this so?
(The prepared nanoparticles were drop casted onto the FTO, Ag/AgCl used as reference, Pt as counter electrode and the electrolyte is 0.5M KOH)