Prediction of (TiO2)x(Cu2O)y alloys for efficient photoelectrochemical water splitting.

The formation of (TiO(2))(x)(Cu(2)O)(y) solid-solutions is investigated using a global optimization evolutionary algorithm. First-principles calculations based on density functional theory are then used to gain insight into the electronic properties of these alloys. We find that: (i) Ti and Cu in (TiO(2))(x)(Cu(2)O)(y) alloys have similar local environments as in bulk TiO(2) and Cu(2)O except for (TiO(2))(Cu(2)O) which has some trigonal-planar Cu ions. (ii) The predicted optical band gaps are around 2.1 eV (590 nm), thus having much better performance in the absorption of visible light compared with both binary oxides. (iii) (TiO(2))(2)(Cu(2)O) has the lowest formation energy amongst all studied alloys and the positions of its band edges are found to be suitable for solar-driven water splitting applications.

First principles study of adsorption of O2 on Al surface with hybrid functionals.

Adsorption of O(2) molecule on Al surface has been a long standing puzzle for the first principles calculation. We have studied the adsorption of O(2) molecule on the Al(111) surface using hybrid functionals. In contrast to the previous local-density approximation/gradient-corrected approximation, the present calculations with hybrid functionals successfully predict that O(2) molecule can be absorbed on the Al(111) surface with a barrier around 0.2-0.4 eV, which is in good agreement with experiments. Our calculations predict that the lowest unoccupied molecular orbital of O(2) molecule is higher than the Fermi level of the Al(111) surface, which is responsible for the barrier of the O(2) adsorption.