Polymer-Mediated Self-Assembly of TiO2@Cu2O Core–Shell Nanowire Array for Highly Efficient Photoelectrochemical Water Oxidation

Abstract

Phototoelectrochemical (PEC) water splitting represents a highly promising strategy to convert solar energy to chemical energy in the form of hydrogen, but its performance is severely limited by the water oxidation reaction. We conformally grew an ultrathin and continuous coating of Cu₂O on TiO₂ nanowire array (NWA) to form a truly core–shell TiO₂@Cu₂O NWA via a new facile, economical, and scalable polymer-mediated self-assembly approach, in which the polymer serves as a stabilizer, reductant, and linker simultaneously. This heteronanostructure was subsequently directly used as a photoanode for PEC water splitting, showing a photocurrent density of 4.66 mA cm^–2 at 1.23 V vs RHE in 0.5 M Na₂SO₄ solution and a maximum photoconversion efficiency of 0.71%, both of which are the highest reported for TiO₂-based photoanodes measured under the same conditions (neutral conditions and without any sacrificial agent). The superior PEC performance of the TiO₂@Cu₂O NWA toward water oxidation is primarily due to much enhanced visible light collection and charge separation for high charge carrier density as well as greatly facilitated charge transfer and transport. This work not only offers a novel TiO₂@Cu₂O core–shell NWA photoanode for highly efficient PEC water oxidation and investigate its enhancement mechanism but also provides scientific insights into the mechanism of the polymer-mediated self-assembly, which can be further extended to fabricate various other core–shell nanoarchitectures for broad applications.