In situ Blue titania via band shape engineering for exceptional solar H2 production in rutile TiO2

Designing an excellent solar photocatalyst based on TiO2 without an external cocatalyst such as Pt remains unresolved despite its exceptional potential for renewable energy production. Here, we report a state-of-the-art solar-driven photocatalytic Cl-doped rutile TiO2, in nanosheet morphology with (110) facets, for H-2 production from water splitting in the absence of any external cocatalyst. The Cl-doped rutile TiO2 nanosheets are easily synthesised via a layered titanate's interconversion through a simple dilute HCl treatment and thermal heating at a convenient temperature. We demonstrate that engineering the band shape can result in long-lasting photogenerated Ti3+, which subsequently can act as an in situ cocatalyst in rutile TiO2. According to our density functional calculations, the Cl dopant has a pivotal role in improving the band shape of TiO2, i.e., significantly reducing the effective mass of the photogenerated electrons and holes, especially when compared to the effect of oxygen vacancy. Consequently, the boosted carrier mobility, resulting from lighter carriers, photogenerates a significant number of prolonged Ti3+ species that enhance photocatalytic activity in situ (i.e., in situ blue titania). Our results show that despite the considerable efforts that have been directed towards narrowing TiO2's band gap, band shape engineering offers a more facile and robust solution for photocatalysis.

Automated summary

This study presents a solar-driven photocatalyst based on Cl-doped rutile TiO2, which improves photocatalytic activity by engineering the band shape of TiO2. The research demonstrates that band shape engineering offers a more facile and robust solution for photocatalysis, compared to previous efforts directed towards narrowing TiO2's band gap.