Construction of WO 3 quantum dots/TiO 2 nanowire arrays type II heterojunction via electrostatic self-assembly for efficient solar-driven photoelectrochemical water splitting.

Construction of a heterojunction between quantum dots and TiO ₂ nanowire arrays via electrostatic self-assembly is rarely reported. In this work, mercury lamp irradiation was used to change the surface potential of WO ₃ quantum dots and TiO ₂ nanowire arrays, resulting in WO ₃ quantum dots tightly attached on the surface of TiO ₂ nanowire through electrostatic self-assembly. Photoelectrochemical measurements showed that the WO ₃ quantum dots formed a type II heterojunction with the TiO ₂ nanowire arrays rather than serving as carrier-trapping sites. In the self-assembly system, the TiO ₂ nanowire arrays provide a charge-transfer channel for the WO ₃ quantum dots, greatly improving the contribution of the WO ₃ quantum dots to the photocurrent. Quantitative calculations showed that the improvement of the bulk carrier-separation efficiency was the reason for the enhanced photoelectrochemical performance of the self-assembled system. The photocurrent density of the optical self-assembled system at 1.23 V ( vs. RHE) was ∼5.5 times as high as that of the TiO ₂ nanowire arrays. More importantly, the self-assembled system exhibited excellent photoelectrochemical stability.