Cu 2 O and CuO Nanocrystalline Photoelectrochemical Systems
Thomas Polson Slide 2 Why use a semiconductor? Absorbed photons
promote electrons to a higher energy state (conductive band)
Electrons from conductive band used to split H 2 O Differing
semiconductors have varying conductive band potentials Conductive
Band Valence Band hh Slide 3 Usable band gap of 1.9 eV 2 H 2 O (l)
O 2 (g) + 4 H + (aq) +4 e E 0 = +1.23 eV 2 H + + 2 e - H 2( g ) E 0
= 0.0 eV Conductive Band higher than Hydrogen -.9 V 1 V hh 1.9V Why
Cu 2 O? Slide 4 Cu 2 O Stability Cu 2 O known to be unstable by
photo degradation when illuminated in H 2 O Cu 2 O + H 2 O + 2e - 2
Cu + OH - -.25ev Nanocrystalline Cu 2 O does not degrade Stability
unexplained Slide 5 Cu 2 O film production Electrochemical
deposition pH Deposition time Sol-gel Commercially available Cu 2 O
CuCl 2 Nanocubes Slide 6 Electrochemical Deposition Working Counter
Reference Cupric Lactate Solution 45g CuSO4 75 mL 85% Lactic acid
225mL 5M NaOH ITO Coated Glass SCE (satd KCl) Pt Slide 7
Electrochemical Deposition Vary time from 15 mins to 2 hrs Longer
time thicker film Vary pH from 8 to 12 pH ~10 most uniform film
Based on Cu 2 O: Electrodeposition and Characterization P.E. de
Jongh, Chem. Mater. 11 3512- 3517 (1999) Photoelectrochemistry of
Electrodeposited Cu 2 O, P.E. de Jongh JES, 147(2) 484-489 (2000).
Slide 8 Electrochemical Deposition Slide 9 Cu 2 O Standard 111222
Highly oriented crystal structure Slide 10 Electrochemical
Deposition Slide 11 Light Current Dark Current Effective
Photocurrent Slide 12 Sol-gel(Cu 2 O) Cu 2 O suspended in H 2 O w/
acetyl acetone and triton X Annealed for 1 hr @ 360C to ITO glass
Adapted from Testing of Dye Sensitized TiO2 Solar Cells I & II
G.P. Smestad SEM&SC 32 259-273 (1994). Slide 13 Sol-gel(Cu 2 O)
Cu 2 O Standard Positive ID of Cu 2 O Random orientation Slide 14
Sol-gel(Cu 2 O) Slide 15 Light Current Effective Photocurrent Dark
Current Slide 16 Sol-gel (Nanocubes) Chemical reduction CuCl 2 + 2
NaOH Cu(OH) 2 + 2 NaCl 4 Cu(OH) 2 + N 2 H 4 Cu 2 O + 6 H 2 O + N 2
Slide 17 Sol-gel (Nanocubes) Nanocubes annealed in same manner as
bulk Cu 2 O Method adapted from Room temperature synthesis of Cu 2
O nanocubes and nanoboxes Z. Wang SSC 130 585-589 (2004) Slide 18
XRD of Nanocubes Cu 2 O CuO Cu 2 OCuO Slide 19 Sol-gel (Nanocubes)
Slide 20 Nanocubes Slide 21 Sol-gel (Nanocubes) Light Current Dark
Current Effective Photocurrent Slide 22 Redox Potentials of
Relevant Rxns E (V vs. SCE) -.5 0 +.5 VB CB Cu 2 O - Cu 2 O + H 2 O
+ 2e - 2Cu + 2OH - - 2CuO + H 2 O + 2e- Cu 2 O + 2OH - - O 2 + 2H 2
O +2e - 2OH - + H 2 O 2 - O 2 + 2H 2 O +4e - 4OH - - 2H + + 2e - H
2 Slide 23 Mechanism of CuO Solar Cell Ox Red h+h+ VB CBe-e- e-e-
e-e- Pt CuO redox couple in solution VB CB EfEf Ph(CN) 2 PhNO 2 PhN
2 AQ BQ 0.00 +0.16 +0.26 -0.52 -0.95 -1.20 -1.33 -1.72 -1.74 AQ =
anthroquinone BQ = benzoquinone Slide 24 Redox Couple Photocurrent
Slide 25 Slide 26 Future of the Project Deposit Pt on
electrodeposited nanocrystalline sheets Couple with n-type
semiconductor Produce hydrogen Slide 27 Thank you Cornell Center
for Materials Research Ithaca Chemistry Department Jacy Spado
Meagan Daniels Akiko Fillinger
