Nanoetching TiO2 nanorod photoanodes to induce high-energy facet exposure for enhanced photoelectrochemical performance

Crystal facet engineering is considered as an effective way to improve photoelectrochemical (PEC) performance. Here, we have developed a nanoetching technology (TiO2 → TiO2/Bi4Ti3O12 → TiO2/BiVO4 → etching-TiO2) to treat rutile TiO2 nanorod films. Interestingly, the technology can induce the exposure of a large number of high energy (101) faces, and the etching-TiO2 film (E-TiO2) showed a significantly enhanced PEC performance. A dynamic study indicates that charge separation and transfer have been obviously improved by such a nanoetching technology. In particular, the charge transfer efficiency (ηtrans) of E-TiO2 reaches 93.4% at 1.23 V vs. RHE without any loaded cocatalyst. The mechanism of PEC performance enhanced by the strategy is experimentally and theoretically unraveled. The improvement of PEC performance is mainly attributed to the shorter distance between H and the neighboring O-b for the HO* intermediates of the rutile (101) facet, which can reduce the energy barrier for the OER. Besides, the driving force for spatial charge separation between the (110) and (101) facets can promote charge separation. This work offers a new and versatile nanotechnology to induce the exposure of the high energy crystal facets and improve the PEC performance.