Table 2 Photocatalytic activation mechanism of TiO2.

From: Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

Reaction

Reference

R1

TiO2 + hν → ecb− + hvb+

40

R2

ecb− + hvb+ → heat

41

R3

hvb+ + H2O → ·OH + H+

42

R4

hvb+ + OH− → ·OH

43

R5

ecb− + O2 → O2·−

41

R6

O2·− + O2·− + 2 H+ → H2O2 + O2

41

R7

O2 + H·(H+ + ecb− → H·) → HO2· O2·− + H+ → HO2·

41, 44

R8

HO2· + H+ + ecb− (H + HO2) → H2O2

45

R9

H2O2 + hν → 2·OH

46

R10

H2O2 + ecb− → ·OH + OH−

41

  1. hν: photons, hvb+: valence band hole, ecb−: conduction band electron, ·OH: hydroxyl radical, OH−: hydroxide, O2·−: superoxide radical, HO2·: hydroperoxyl radical, H2O2: hydrogen peroxide.
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