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First principles study of the photo-oxidation of water on tungsten trioxide
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10.1063/1.3088845
/content/aip/journal/jcp/130/11/10.1063/1.3088845
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/11/10.1063/1.3088845

Figures

Image of FIG. 1.
FIG. 1.

Relaxed unit cell. Tungsten atoms are represented by light (yellow) spheres and oxygen atoms by dark (red) spheres.

Image of FIG. 2.
FIG. 2.

Repeating three-unit cell slab for the 200 surface. Tungsten atoms are represented by light (yellow) spheres and oxygen atoms by dark (red) spheres. We include the same number of coverage oxygen atoms in the lower surface, fixed in the bulk positions, and in the upper surface, in the relaxed positions.

Image of FIG. 3.
FIG. 3.

The phase diagram of the (200) surface system calculated as function of the potential at . The free energy of surface with no oxygen on top of the tungsten atoms plus four water molecules is taken as energy zero.

Image of FIG. 4.
FIG. 4.

The phase diagram of the (020) surface system calculated as function of the potential at . The free energy of surface with no oxygen on top of the tungsten atoms plus four water molecules is taken as energy zero.

Image of FIG. 5.
FIG. 5.

The phase diagram of the (002) surface system calculated as function of the potential at . The free energy of surface with no oxygen on top of the tungsten atoms plus four water molecules is taken as energy zero.

Image of FIG. 6.
FIG. 6.

Top view of the diagonal arrangement of the half-monolayer coverage of oxygen atoms of the (002) surface in the presence of molecular oxygen. Tungsten atoms are represented by light (yellow) spheres and oxygen atoms by dark (red) spheres.

Image of FIG. 7.
FIG. 7.

Free energies of the intermediates for different values of the applied potential for . (, , and ) are depicted for . At the equilibrium potential some reaction steps are uphill in free energy. At 2.27 V all reaction steps are downhill in free energy. For this material, we compare to the case with , the corresponding values of the redox potential vs NHE for the photogenerated holes in the valence band of in contact with .

Image of FIG. 8.
FIG. 8.

Free energies of the intermediates for different values of the applied potential for . (, , and ) are depicted for . At the equilibrium potential some reaction steps are uphill in free energy. At 2.33 V all reaction steps are downhill in free energy. For this material, we compare to the case with , the corresponding values of the redox potential vs NHE for the photogenerated holes in the valence band of in contact with .

Image of FIG. 9.
FIG. 9.

Free energies of the intermediates for different values of the applied potential for . (, , and ) are depicted for . At the equilibrium potential some reaction steps are uphill in free energy. At 2.28 V all reaction steps are downhill in free energy. For this material, we compare to the case with , the corresponding values of the redox potential vs NHE for the photogenerated holes in the valence band of in contact with .

Tables

Generic image for table
Table I.

Convergence test results for the monoclinic unit cell. Total energy is presented as a function of the -point mesh and the energy cutoff .

Generic image for table
Table II.

Lattice parameters and volume of the monoclinic unit cell. Comparison with previous calculations and experiment.

Generic image for table
Table III.

Convergence test results for the energy of an oxygen atom on top of a tungsten atom on the bare 200 surface of , , as a function of the thickness of the slab, the -point mesh, the energy cutoff and the total length of the box (slab thickness plus vacuum length in terms of number of unit cells in the direction perpendicular to the slab).

Generic image for table
Table IV.

Energy differences for the lower surface, between the surface covered by , 2, 3, and 4 oxygen atoms and the bare surface. F accounts for the different crystal faces of 200, 020, and 002. In this calculation, every ion is fixed in the bulk unit cell position.

Generic image for table
Table V.

Components of the free energy change (eV) in the relative stability calculation of the different surface terminations.

Generic image for table
Table VI.

Change in the free energy at standard conditions, , for the different oxygen coverages of the (002) surface. For the half-monolayer coverage we include the results for the diagonal termination and for the most favorable linear termination.

Generic image for table
Table VII.

Change in the free energy coming from the differences in zero point energies, , and the change in entropy for the different reaction steps.

Generic image for table
Table VIII.

Energy change (eV) between the reaction steps in the water oxidation process, for the different surfaces terminations .

Generic image for table
Table IX.

Change in the free energy at standard conditions, (eV), for the relevant surfaces terminations in the water oxidation process.

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/content/aip/journal/jcp/130/11/10.1063/1.3088845
2009-03-16
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: First principles study of the photo-oxidation of water on tungsten trioxide (WO3)
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/11/10.1063/1.3088845
10.1063/1.3088845
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