attacked by another adsorbed H 2 O, two adjacent Ti À O
À centers can couple with
each other to form surface peroxide species. The surface peroxide intermediate
would be oxidized by photoinduced holes to form TiÀO 2
À species, which can be
further oxidized by the photoinduced hole, forming an O 2 molecule followed by the
recovery of OH B group. The excessive H 2 O molecules adsorb on the regenerated
OH B groups, which may hinder the interaction between the O 2 molecule and the
TiO 2 surface and further prevent the O 2 molecule from trapping the photoinduced
electron to form TiÀO 2
À species. Then the O 2 molecule would interact with the
cocatalyst Pt and be reduced to form PtÀO 2
À species by the photoinduced electron.
The reduction of O 2
À species by the photoinduced electron (O 2
À + 2H
+ +
e ! H 2 O 2 + 2H
+ + 2e ! 2H 2 O) should be responsible for the low efficiency of
the photocatalytic water splitting. Meanwhile, the reduction of H
+ from the above
recycle by photoinduced electrons on the cocatalyst Pt produces the H 2 molecule.
References
1. Nosaka Y, Nosaka AY (2017) Generation and detection of reactive oxygen species in
photocatalysis. Chem Rev 117:11302–11336
2. Hirakawa T, Nosaka Y (2008) Selective production of superoxide ions and hydrogen peroxide
over nitrogen- and sulfur-doped TiO 2 photocatalysts with visible light in aqueous suspension
systems. J Phys Chem C 112:15818–15823
3. Wang D, Zhao L, Guo LH et al (2014) Online detection of reactive oxygen species in ultraviolet
(UV)-irradiated nano-TiO 2 suspensions by continuous flow chemiluminescence. Anal Chem
86:10535–10539
4. Kakuma Y, Nosaka AY, Nosaka Y (2015) Difference in TiO 2 photocatalytic mechanism
between rutile and anatase studied by the detection of active oxygen and surface species in
water. Phys Chem Chem Phys 17:18691–18698
5. Ishibashi K, Fujishima A, Watanabe T et al (2000) Hashimoto, K. Generation and deactivation
processes of superoxide formed on TiO 2 film illuminated by very weak UV light in air or water.
J Phys Chem B 104:4934–4938
6. Dimitrijevic NM, Rozhkova E, Rajh T (2009) Dynamics of localized charges in dopaminemodified TiO 2 and their effect on the formation of reactive oxygen species. J Am Chem Soc
131:2893–2899
7. Tachikawa T, Majima T et al (2010) Single-molecule, single-particle fluorescence imaging of
TiO 2 -based photocatalytic reactions. Chem Soc Rev 39:4802–4819
8. Naito K, Tachikawa T, Fujitsuka M et al (2008) Real-time single-molecule imaging of the
spatial and temporal distribution of reactive oxygen species with fluorescent probes: applications to TiO 2 photocatalysts. J Phys Chem C 112:1048–1059
9. Xu W, Jain PK, Beberwyck BJ et al (2012) Probing redox photocatalysis of trapped electrons
and holes on single Sb-doped titania nanorod surfaces. J Am Chem Soc 134:3946–3949
10. Kim W, Tachikawa T, Moon G et al (2014) Molecular-level understanding of the photocatalytic
activity difference between anatase and rutile nanoparticles. Angew Chem Int Ed
53:14036–14041
11. Tachikawa T, Wang N, Yamashita S et al (2010) Design of a highly sensitive fluorescent probe
for interfacial electron transfer on a TiO 2 surface. Angew Chem Int Ed 49:8593–8597
12. Tachikawa T, Yamashita S, Majima T (2011) Evidence for crystal-face-dependent TiO 2
photocatalysis from single-molecule imaging and kinetic analysis. J Am Chem Soc
133:7197–7204
References
43
À centers can couple with
each other to form surface peroxide species. The surface peroxide intermediate
would be oxidized by photoinduced holes to form TiÀO 2
À species, which can be
further oxidized by the photoinduced hole, forming an O 2 molecule followed by the
recovery of OH B group. The excessive H 2 O molecules adsorb on the regenerated
OH B groups, which may hinder the interaction between the O 2 molecule and the
TiO 2 surface and further prevent the O 2 molecule from trapping the photoinduced
electron to form TiÀO 2
À species. Then the O 2 molecule would interact with the
cocatalyst Pt and be reduced to form PtÀO 2
À species by the photoinduced electron.
The reduction of O 2
À species by the photoinduced electron (O 2
À + 2H
+ +
e ! H 2 O 2 + 2H
+ + 2e ! 2H 2 O) should be responsible for the low efficiency of
the photocatalytic water splitting. Meanwhile, the reduction of H
+ from the above
recycle by photoinduced electrons on the cocatalyst Pt produces the H 2 molecule.
References
1. Nosaka Y, Nosaka AY (2017) Generation and detection of reactive oxygen species in
photocatalysis. Chem Rev 117:11302–11336
2. Hirakawa T, Nosaka Y (2008) Selective production of superoxide ions and hydrogen peroxide
over nitrogen- and sulfur-doped TiO 2 photocatalysts with visible light in aqueous suspension
systems. J Phys Chem C 112:15818–15823
3. Wang D, Zhao L, Guo LH et al (2014) Online detection of reactive oxygen species in ultraviolet
(UV)-irradiated nano-TiO 2 suspensions by continuous flow chemiluminescence. Anal Chem
86:10535–10539
4. Kakuma Y, Nosaka AY, Nosaka Y (2015) Difference in TiO 2 photocatalytic mechanism
between rutile and anatase studied by the detection of active oxygen and surface species in
water. Phys Chem Chem Phys 17:18691–18698
5. Ishibashi K, Fujishima A, Watanabe T et al (2000) Hashimoto, K. Generation and deactivation
processes of superoxide formed on TiO 2 film illuminated by very weak UV light in air or water.
J Phys Chem B 104:4934–4938
6. Dimitrijevic NM, Rozhkova E, Rajh T (2009) Dynamics of localized charges in dopaminemodified TiO 2 and their effect on the formation of reactive oxygen species. J Am Chem Soc
131:2893–2899
7. Tachikawa T, Majima T et al (2010) Single-molecule, single-particle fluorescence imaging of
TiO 2 -based photocatalytic reactions. Chem Soc Rev 39:4802–4819
8. Naito K, Tachikawa T, Fujitsuka M et al (2008) Real-time single-molecule imaging of the
spatial and temporal distribution of reactive oxygen species with fluorescent probes: applications to TiO 2 photocatalysts. J Phys Chem C 112:1048–1059
9. Xu W, Jain PK, Beberwyck BJ et al (2012) Probing redox photocatalysis of trapped electrons
and holes on single Sb-doped titania nanorod surfaces. J Am Chem Soc 134:3946–3949
10. Kim W, Tachikawa T, Moon G et al (2014) Molecular-level understanding of the photocatalytic
activity difference between anatase and rutile nanoparticles. Angew Chem Int Ed
53:14036–14041
11. Tachikawa T, Wang N, Yamashita S et al (2010) Design of a highly sensitive fluorescent probe
for interfacial electron transfer on a TiO 2 surface. Angew Chem Int Ed 49:8593–8597
12. Tachikawa T, Yamashita S, Majima T (2011) Evidence for crystal-face-dependent TiO 2
photocatalysis from single-molecule imaging and kinetic analysis. J Am Chem Soc
133:7197–7204
References
43