Well aligned ZnO nanowires were synthesized on Si wafer using thermal chemical vapor deposition (thermal-CVD). Then, amorphous TiO2 shell is coated on pristine ZnO NWs by thermal CVD. Shell thickness can be controlled depending on time and it influences the efficiency of photoconversion in photoelectrochemical water splitting. The best efficiency was obtained when its shell thickness is 15 nm, and this value is higher than that of pristine ZnO NWs. Morphology of ZnO NWs was characterized by scanning electron microscope (SEM) and the crystallinity was characterized by X-ray Diffraction Spectroscopy (XRD) and Raman spectroscopy. Morphology of TiO2 shell and its thickness were characterized by transmission electron microscope (TEM) and Energy-dispersive X-ray spectroscopy (EDX).