Applied vs fundamental research in heterogeneous photocatalysis: problems and perspectives. An introduction to 'physical principles of photocatalysis'

In Situ Construction of Bronze/Anatase TiO2 Homogeneous Heterojunctions and Their Photocatalytic Performances

Photocatalytic degradation is one of the most promising emerging technologies for environmental pollution control. However, the preparation of efficient, low-cost photocatalysts still faces many challenges. TiO2 is a widely available and inexpensive photocatalyst material, but improving its catalytic degradation performance has posed a significant challenge due to its shortcomings, such as the easy recombination of its photogenerated electron-hole pairs and its difficulty in absorbing visible light. The construction of homogeneous heterojunctions is an effective means to enhance the photocatalytic performances of photocatalysts. In this study, a TiO2(B)/TiO2(A) homogeneous heterojunction composite photocatalyst (with B and A denoting bronze and anatase phases, respectively) was successfully constructed in situ. Although the construction of homogeneous heterojunctions did not improve the light absorption performance of the material, its photocatalytic degradation performance was substantially enhanced. This was due to the suppression of the recombination of photogenerated electron-hole pairs and the enhancement of the carrier mobility. The photocatalytic ability of the TiO2(B)/TiO2(A) homogeneous heterojunction composite photocatalyst was up to three times higher than that of raw TiO2 (pure anatase TiO2).

Role of surface termination in forming type-II photocatalyst heterojunctions: the case of TiO2/BiVO4

In this work we investigate TiO₂ and BiVO₄ nanostructures by means of density functional theory (DFT) calculations, to provide an estimate of the band alignment in TiO₂/BiVO₄ interfaces, highly active in photo-electrochemistry and photocatalytic water splitting. Calculations were carried out with both DFT range separated and self-consistent dielectric dependent hybrid functionals (HSE06 and PBE0_DD). The impact of systems' size has been investigated. The converged electronic levels of TiO₂ and BiVO₄ surfaces have been used to predict the band alignment in TiO₂/BiVO₄ heterostructures. Results indicated that when TiO₂ (101) surface is matched with BiVO₄ (110), a type-II alignment is obtained, where the band edges of BiVO₄ are higher in energy that those of TiO₂. This picture is favorable for charge-carriers separation upon photoexcitation, where electrons move toward TiO₂ and holes toward BiVO₄. On the contrary, if TiO₂ (101) is interfaced to BiVO₄ (010) the offset between the band edges is negligible, thus reducing the driving force toward separation of charge carriers. These results rationalize the dependence on the facet's exposure of the observed photocatalytic performances of TiO₂/BiVO₄ composites, where the TiO₂ (101)/BiVO₄ (110) interface outperforms the TiO₂ (101)/BiVO₄ (010) one.