1. Photoelectrochemical Water Splitting for Hydrogen Production Using Carbon Modified (CM) n-TiO 2 Chengkun Xu and Shahed U. M. Khan * Duquesne University, Pittsburgh, PA [email_address] Chemistry & Biochemistry
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4. Photoelectrochemial Water Splitting Photoanode: 2H 2 O + 4h O 2 + 4H + Cathode: 4H + + 4e 2H 2 Inputs: sunlight and water Outputs: hydrogen and oxygen Sustainable and environmentally benign e n-type E g H 2 O O 2 Pt H 2 O H 2 h e 2H 2 O O 2 + 2H 2
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9. UV-Vis spectra of CM-n-TiO 2 films Chengkun Xu and Shahed Khan, Electrochemical and Solid-State Letters, 10 (3) B56-B59, 2007 C at% 1 0 2 0.58 3 0.94 4 2.0
10. Dependence of Photoresponse on the Carbon Doping Concentration C at% 1 0 2 0.58 3 0.94 4 2.0 Chengkun Xu and Shahed UM Khan, Electrochemical and Solid-State Letters, 10 (3) B56-B59, 2007
11. Dependence of Photoresponse on the Carbon Doping Concentration 1, 3-calcined in Ar; 3.8 at % C 2, 4-calcined in air; 2.1 at % C 2.1 at % C 3.8 at % C Chengkun Xu and Shahed UM Khan, Electrochemistry Communications 8 (2006) 1650–1654 Mostly visible light illumination White light illumination 1, 2-illuminated with white light 3, 4-illuminated with mostly visible light
12. Monochromatic Photocurrent The photoresponse in the UV region now extends into the visible region ( bandgap reduction ). A second photoresponse in the visible region at around 600 nm noted ( new intragap band ). Chengkun Xu and Shahed UM Khan, Electrochemical and Solid-State Letters, 10 (3) B56-B59, 2007 Visible UV
13. Quantum Efficiency η Chengkun Xu and Shahed UM Khan, Electrochemical and Solid-State Letters, 10 (3) B56-B59, 2007
14. Bandgap Energy of CM-n-TiO 2 Chengkun Xu and Shahed UM Khan, Electrochemical and Solid-State Letters, 10 (3) B56-B59, 2007 Chengkun Xu and Shahed UM Khan, Electrochemistry Communications 8 (2006) 1650–1654
15. Schematic Diagram of Bandgap Modifications for CM-n-TiO 2 H 2 O/H 2 O 2 /H 2 O 1.23 eV 2.63 eV 1.2 eV E C E V Intragap band h ν h ν CM-n-TiO 2 KOH Undoped TiO 2 Carbon-doped TiO 2
16. Explanations of Bandgap Modifications H. Kamisaka et al, J Chem. Phys. 123, 084704 (2005) Carbon doping induces several intragap states. The intragap states near the valence band edge overlap with the valence band and form a new valence band and thus narrow the bandgap of TiO 2 . The states deep in the gap stand alone.
17. Visible Light Photocatalytic degradation of 4-chlorophenol Using CM-n-TiO 2 Nanoparticles CM-n-TiO 2 nanoparticles show significant visible light catalytic activity Under mostly visible light illumination P25 TiO 2 CM-n-TiO 2 Chengkun Xu and Shahed UM Khan, Applied Catalysis B: Environmental, 64 (2006), 312-317
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