The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO₂. The discovery of the photolysis of water on the surface of TiO₂ in 1972 launched four decades of intensive research into the underlying chemical and physical processes involved. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO₂ (ref. ). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.

We summarise current state-of-the-art efficient visible-light driven heterojunction water splitting photo(electro)catalysts and describe how theoretical modelling of electronic structures at interfaces can explain their functionality.

The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low-cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported. The g-C3N4 exhibits an extraordinary hydrogen-evolution rate (ca. 20 000 μmol h−1 g−1 under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 % under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced.

Passivated phosphorene nanoribbons, armchair (a-PNR), 7 diagonal (d-PNR), and zigzag (z-PNR), were investigated using density 8 functional theory. Z-PNRs demonstrate the greatest quantum size effect, 9 tuning the bandgap from 1.4 to 2.6 eV when the width is reduced from 26 to 6 10 Å. Strain effectively tunes charge carrier transport, leading to a sudden increase 11 in electron effective mass at +8% strain for a-PNRs or hole effective mass at 12 +3% strain for z-PNRs, differentiating the (m h */m e *) ratio by an order of otherwise, we present results using crystal lattices, geometries,