Tungsten Oxide Nano Flower Surface Barrier Model

Due to the presence of contact junctions in tungsten oxide nanoflowers, nanostructures that cross each other have different atomic adsorptions and thus different surface electronic states. Different surface states of electrons will form different surface potentials and a surface barrier appears at their contact junctions.

Oxygen molecules and hydrogen molecules adsorbed on the surface of tungsten oxide nano flower surface energy barrier change process can be divided into the following three cases:

（1）When the Pt surface modified tungsten oxide nanoflower film is only exposed to the air, the oxygen molecules are easily adsorbed on the Pt particles, and the oxygen molecules are separated into oxygen atoms by the Pt particles or tungsten oxide and transferred to the tungsten oxide nanoflower. The oxygen atoms then trap the free electrons in the tungsten oxide conduction band to form different adsorbed oxygen ions. These oxygen ions will be distributed on the tungsten oxide nano flower due to the spillover effect. And have a repulsive effect on the electrons, resulting in the formation of an electron barrier between the tungsten oxide nanoflowers. Hinder the transfer of electrons between the tungsten oxide nanoflowers, thus macroscopically showing an increase in resistance.

（2）When the Pt surface modified tungsten oxide nanoflower film only in hydrogen, hydrogen molecules adsorbed on the Pt surface. Unstable hydrogen bonds on the hydrogen are easily catalyzed by Pt to form hydrogen atoms, which will be distributed on the tungsten oxide nano flower due to the spillover effect. Hydrogen atoms decompose on the surface of tungsten oxide into hydrogen ions and electrons.

（3）When the Pt surface-modified tungsten oxide nanoflower film has an atmosphere of air and hydrogen, oxygen ions and hydrogen ions will be simultaneously present on the surface of the tungsten oxide nanowire. Hydrogen ions will react with oxygen ions to form water molecules and be released from the tungsten oxide surface, resulting in a decrease in the concentration of oxygen ions. As a result, the electron barrier between the nanoflowers is reduced, and the electron transfer efficiency between the nanoflowers is increased. On the macro performance of the resistance decreased. Therefore, as the hydrogen concentration changes, the hydrogen ion concentration on the surface of the nanoflower will be changed correspondingly. The macroscopic manifestation is the electric resistance produces the corresponding change.

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