Dye-sensitized photoelectrochemical cell on plasmonic Ag/AgCl @ chiral TiO2 nanofibers for treatment of urban wastewater effluents, with simultaneous production of hydrogen and electricity

Abstract

The feasibility of simultaneous production of hydrogen and electricity with simultaneous contaminants removal from “actual” urban wastewater within a dye-sensitized photoelectrochemical cell (DSPC) is demonstrated for the first time. The photoanode in the DSPC was a novel nanostructured plasmonic Ag/AgCl @ chiral TiO2 nanofibers (Ag and AgCl nanoparticles supported on chiral TiO2 nanofibers). The electrolyte in the DSPC was actual wastewater to which an estrogen (17-β-ethynylestradiol, EE2) and a heavy metal (Cu2+) were added. The contaminants in the wastewater rather than I−/I3− (usual electrolyte in conventional DSPCs) acted as electrons’ bridges for the stabilization of charges in this DSPC. Almost total removal of total organic carbon (TOC), Cu2+, EE2, and 70% removal of total nitrogen (TN) were achieved under visible-light irradiation. A relatively high solar energy conversion efficiency (PCE 3.09%) was recorded and approximately 98% of the electricity was converted to H2 after the consumption of dissolved oxygen (DO), Cu2+ and TN. This performance was attributed to the “symbiotic” relationship between the TiO2 chiral nanofibers and the plasmonic effect of Ag nanoparticles at the photoanode, although Ag may act as a recombination site which may hinder the generation of electricity. The dye N719 in this study exhibited a temporary sensitization effect, and a more efficient sensitizer is expected to be studied in the future. This study opens up new opportunities for producing renewable energy from wastewater treatment processes including organic and inorganic matter as viable resources.