Preparation of freestanding porous silicon/ZnO composites and its supercapacitor property

Two step anodic oxidation method was firstly used to prepare freestanding porous silicon. Then ZnO nanocrystal layer was deposited in the freestanding porous silicon using vacuum filtration method and hydro-thermal synthesis approach was used for further growth of ZnO nanocrystals finally. The morphology, element and luminescence properties of the samples were characterized by scanning electron microscope, X-ray energy dispersive spectrum analysis and photoluminence spectrum analysis. The results show that ZnO nanoparticles exist in the freestanding porous silicon and porous silicon/ZnO composites form successfully. Moreover, the electrochemical tests of the composites as a supercapacitor electrode was conducted by cyclic voltamerty, impendance spectrum and galvanostatic charge/discharge tests. The composites have good supercapacitor property. The specific capacitances can reach 15.7 F/g, with an increase of 120 times compared with the freestanding porous silicon.