Enhanced photocatalytic activity of hydrogen evolution through Cu incorporated ZnO nano composites

Abstract

Green environment friendly and economical light responsive photocatalytic method was used to investigate the improving H2 efficiency of ZnO by Cu doping. Efficient nano composites of ZnO doped with varying percentage of copper (0.0, 0.01, 0.03 and 0.05 mol.%) were synthesized by sol-gel method to analyze H2 evolution. Cu incorporation did not change the hexagonal wurtzite structure of ZnO nanoparticles as examined by x-ray diffraction (XRD). EDX indicates no external trace found in Cu doped ZnO samples and surface area decrease by increasing Cu contents in ZnO proved by BET. Morphology of particles through scanning electron microscopy (SEM) is nearly spherical. Diffuse reflectance spectroscopy (DRS) was utilized to determine the energy band gap (Eg). Cu incorporation into ZnO decreased energy band gap from 3.19 eV to 3.00 eV. XPS shows electronic state of nanoparticles. Recombination rate of photo induced electrons and holes analyzed by photoluminescence spectroscopy (PL) decreased by increase in Cu doping percentage. Further the reduced recombination rate was examined by electrochemical impedance spectroscopy (EIS) and photocurrent density. EIS and photocurrent density are in good affiliation with photoluminescence results. Cu incorporated ZnO catalysts caused an enhancement in H2 production from 7.49 μmol g-1 to 41.55 μmol g-1. Such improvement in H2 production by Cu doped ZnO nanoparticles is due to the reduced recombination of electrons and holes during photocatalytic reaction.