How titanium dioxide crystals on noxer block catalyse oxidation reaction that remove NOx from the atmosphere?

Answer

Titanium dioxide absorbs the radiation which is given off from the sun. This excites the electrons in titanium dioxide to a higher energy level.

The high energy electron from titanium dioxide reacts with oxygen to produce a superdioxide ion on the surface of the titanium dioxide crystals;

O₂ +e- O₂-

Water also reacts with the oxide to produce a hydrogen, hydroxyl radical and an electron which is given back to the titanium dioxide;

H₂O + O₂ H⁺ + OH + e-

"The overall reaction is therefore;

H₂O + O₂ H⁺ + O₂^- + OH"

The hydroxyl radical formed can then oxidise nitrogen dioxide to nitrate ions because it is a very powerful oxidising agent;

NO₂ + OH H⁺ + NO₃^-

More of the nitrogen gases can be rendered as the superoxide produced on the surface of titanium oxide can be used to convert nitrogen monoxide into nitrate ions;

NO + O₂^- NO₃^-

Answer

Titanium dioxide absorbs the radiation which is given off from the sun. This excites the electrons in titanium dioxide to a higher energy level.

The high energy electron from titanium dioxide reacts with oxygen to produce a superdioxide ion on the surface of the titanium dioxide crystals;

O₂ +e- O₂-

Water also reacts with the oxide to produce a hydrogen, hydroxyl radical and an electron which is given back to the titanium dioxide;

H₂O + O₂ H⁺ + OH + e-

"The overall reaction is therefore;

H₂O + O₂ H⁺ + O₂^- + OH"

The hydroxyl radical formed can then oxidise nitrogen dioxide to nitrate ions because it is a very powerful oxidising agent;

NO₂ + OH H⁺ + NO₃^-

More of the nitrogen gases can be rendered as the superoxide produced on the surface of titanium oxide can be used to convert nitrogen monoxide into nitrate ions;

NO + O₂^- NO₃^-