Baochang Wang

Mo- and N-doped BiNbO4 for photocatalysis applications

The electronic structure of pure BiNbO4 has been calculated and their electronic band positions have been aligned with respect to the water oxidation/reduction potential. The effect of cationic (Mo), anionic (N), and co-doping (Mo-N) on BiNbO4 has been studied and discussed with respect to the standard redox potential levels. Our results show that co-doping of Mo and N in BiNbO4 reduces the band gap up to 31.8%, thus making it a potential candidate for the photocatalysis of water for hydrogen production. The relative stability between the mono- and co-doped BiNbO4 materials show that co-doped material is more stable and feasible in comparison to the mono-doped materials.

Band gap engineering in BiNbO4 for visible-light photocatalysis

We have investigated the electronic structure of anionic mono- (S, N, and C) and co-doping (N-N, C-N, S-C, and S-N) on BiNbO4 for the visible-light photocatalysis. The maximum band gap reduction of pure BiNbO4 is possible with the (C-S) co-doping and minimum with N mono-doping. The calculated binding energies show that the co-doped systems are more stable than their mono-doped counterparts. Our optical absorption curves indicate that the mono- (C) and co-anionic doped (N-N and C-S) BiNbO4 systems are promising materials for visible light photocatalysis.

Hole mediated coupling in Sr2Nb2O7 for visible light photocatalysis

The band gap reduction and effective utilization of visible solar light are possible by introducing the anionic hole-hole mediated coupling in Sr(2)Nb(2)O(7). By using the first principles calculations, we have investigated the mono- and co-anionic doping (S, N and C) in layered perovskite Sr(2)Nb(2)O(7) for the visible-light photocatalysis. Our electronic structure and optical absorption study shows that the mono- (N and S) and co-anionic doped (N-N and C-S) Sr(2)Nb(2)O(7) systems are promising materials for the visible light photocatalysis. The calculated binding energies show that if the hole-hole mediated coupling could be introduced, the co-doped systems would be more stable than their respective mono-doped systems. Optical absorption curves indicate that doping S, (N-N) and (C-S) in Sr(2)Nb(2)O(7) can harvest a longer wavelength of the visible light spectrum as compared to the pure Sr(2)Nb(2)O(7) for efficient photocatalysis.

Molecular simulation for gas adsorption at NiO (100) surface.

Density functional theory (DFT) calculations have been employed to explore the gas-sensing mechanisms of NiO (100) surface on the basis of energetic and electronic properties. We have calculated the adsorption energies of NO(2), H(2)S, and NH(3) molecules on NiO (100) surface using GGA+U method. The calculated results suggest that the interaction of NO(2) molecule with NiO surface becomes stronger and contributes more extra peaks within the band gap as the coverage increases. The band gap of H(2)S-adsorbed systems decrease with the increase in coverage up to 0.5 ML and the band gap does not change at 1 ML because H(2)S molecules are repelled from the surface. In case of NH(3) molecular adsorption, the adsorption energy has been increased with the increase in coverage and the band gap is directly related to the adsorption energy. Charge transfer mechanism between the gas molecule and the NiO surface has been illustrated by the Bader analysis and plotting isosurface charge distribution. It is also found that that work function of the surfaces shows different behavior with different adsorbed gases and their coverage. The work function of NO(2) gas adsorption has a hill-shaped behavior, whereas H(2)S adsorption has a valley-shaped behavior. The work function of NH(3) adsorption decreases with the increase in coverage. On the basis of our calculations, we can have a better understanding of the gas-sensing mechanism of NiO (100) surface toward NO(2), H(2)S, and NH(3) gases.