Ultrathin corrugated nanowire TiO2 as a versatile photoanode platform for boosting photoelectrochemical alcohol and water oxidation

Abstract

Ultrathin semiconductor nanowires are promising alternatives to nanoparticle or bulk counterparts for the construction of photoanodes for solar energy conversion, because of their profuse surface reactive sites and excellent charge transport properties. Herein, well-aligned ultrathin corrugated nanowire TiO₂ (UCW-TiO₂) thin films with a diameter of 10 nm grown on fluorine-doped tin oxide (FTO) substrates by a unique monomicelle-directed assembly method are applied as a versatile photoanode platform. On this platform, photoanodes were used for direct photoelectrochemical (PEC) benzyl alcohol oxidation and can also be dye-sensitized for visible-light driven water oxidation. The conversion of benzyl alcohol (BA) over the pristine UCW-TiO₂ photoanode is close to 100%, and the selectivity can reach 90.2% with a faradaic efficiency of 93% after 15 h. With surface anchoring of a suitable chromophore and oxygen evolution catalysts (OECs), the dye-sensitized UCW-TiO₂ photoanode achieves 5-fold larger faradaic efficiency for water oxidation than that of a spherically structured TiO₂ assembled photoanode. Electrochemical and spectroscopic measurements demonstrate that the ultrathin corrugated nanowire structured TiO₂ accelerates electron transport kinetics and suppresses recombination of surface accumulated holes and electrons compared with spherically structured TiO₂. Both BA oxidation and water oxidation studies show that the UCW-TiO₂ is a versatile photoanode platform for a variety of highly efficient solar energy conversion applications.