Abstract:
Density Functional Theory (DFT) calculations study of Cu doped {0001} and {01-12}
surfaces of hematite for enhanced water splitting have been carried out. The doping was
restricted to planes in the vicinity of the surface, specifically from the top most layers to the
third inner layer of Fe atoms. Thermodynamic stabilities were evaluated based on surface
energies and formation energies. The evaluation of thermodynamic stabilities (negative
formation energy values) shows that the systems are thermodynamically stable which suggest
that they can be synthesized in the laboratory under favorable conditions. Doping on the top
most layer yields the energetically most favorable structure. The calculated charge density
difference plots showed the concentration of charge mainly at the top of the surface
(termination region), and this charge depleted from the Cu atom to the surrounding Fe and O
atoms. This phenomenon (concentration of charge at the top of the surface) is likely to
reduce the distance moved by the charge carriers, decrease in charge recombination
leading to facile transfer of charge to the adsorbate and, suggesting improved
photoelectrochemical water oxidation activity of hematite. The analysis of electron electronic
structure reveals that Cu doped surface systems does not only decrease the band gap but also
leads to the correct conduction band alignment for direct water splitting without external bias
voltage.
