The electronic, optical and water splitting properties in two-dimensional hematite Fe2O3 semiconductors with uniaxial, biaxial strain studied by first principles

Two-dimensional (2D) hematite Fe2O3 is an important semiconductor, optical material and photocatalyst. We here studied the electronic, optical and water splitting properties of recent synthesized 2D Fe2O3 under uniaxial and biaxial strain using first principles with SCAN Meta-GGA plus U method, which can guarantee the accuracy of our results. We can modulate these properties of 2D hematite Fe2O3 with uniaxial, biaxial strain. Tensile strain can increase the bond length of 2D Fe2O3, thus can decreases the overlap of electronic cloud and the bonding of atoms to electrons. The decrease of the overlap of electronic cloud can induce an increase of band gap, while the decrease of the bonding of atoms to electrons can induce a decrease of band gap. The decrease of the overlap of electronic cloud is dominant and the band gap increases with ≤4% strain, while the decrease of bonding of electrons is dominant and the band gap decreases with >4% strain. The increase in band gap shifts the response of optical properties to a higher photon energy in 2D hematite Fe2O3. The applied strain can shift the band alignment to a proper region, which can guarantee 2D hematite Fe2O3 used in water splitting. 2D Fe2O3 with compressive strain has a better performance in the visible region. 2D Fe2O3 can only be oxidized and used for oxygen production without applied strain, which means the water splitting performance of 2D Fe2O3 should be improved by strain. Fortunately, we find out that Fe2O3 has a better water splitting performance when 6% uniaxial in the X direction and 4% biaxial tensile strain are applied, and now the redox ability is enhanced and Fe2O3 is more suitable for photocatalytic hydrolysis. Our work provides a useful reference for the applications of 2D Fe2O3, such as a potential platform of photoelectric devices and photocatalyst in future.