Copper oxide nanoparticle made by flame spray pyrolysis for photoelectrochemical water splitting – Part II. Photoelectrochemical study
By Chiang, Chia-Ying; Aroh, Kosi; Franson, Nicholas; Satsangi, Vibha Rani; Dass, Sahab & Ehrman, Sheryl
Published in International Journal of Hydrogen Energy
2011
Abstract
A scalable method for hydrogen generation by splitting water via a photoelectrochemical cell was studied. Flame spray pyrolysis and spin coating processing methods were used for preparing copper oxide nanoparticles and copper oxide photocathodes. Copper oxide p-type semiconductor nanoparticles made by flame spray pyrolysis were spin coated on conducting ITO substrates and served as photocathodes for photoelectrochemical splitting of water. The film thickness was controlled by the concentration of the CuO suspension solution and numbers of layer deposited on the substrate. As sintering temperature increased to 600 °C, crystalline diameter increased from 28Â nm (before sintering) to 110Â nm and the bandgaps decreased from 1.68Â eV to 1.44Â eV. A 387Â nm thickness CuO film with bandgap 1.44Â eV was demonstrated to have 1.48% total conversion efficiency and 0.91% photon-to-hydrogen generation efficiency. The net photocurrent density (photocurrent – dark current) was measured to be 1.20Â mA/cm2 at applied voltage of -0.55Â V vs. Ag/AgCl in 1Â M KOH electrolyte with 1 sun (AM1.5G) illumination. Based on the Mott–Schottky plot, the carrier density was estimated to be 1.5Â X Â 1021Â cm-3 and the flatband potential to be 0.23Â V vs. Ag/AgCl. Furthermore, the valence band edge and conduction band levels were found to lie at -5.00Â eV and -3.56Â eV respect to the vacuum respectively.