Post on 19-Jun-2015
description
transcript
Notre Dame Radiation LaboratoryDepartment of Chemical and Biomolecular Engineering1
Deparment of Chemistry and Biochemistry2
University of Notre Dame, Notre Dame, IN 46556
2
J. Phys. Chem. Lett., 2011, 2 (19), pp 2453–2460DOI: 10.1021/jz201064k
Motivation
•Cu2S exhibits exceptional redox activity in aqueous polysulfide solutions1
•Brass is a commonly used counter electrode in laboratory assessments but degrades over time
•Reduced graphene oxide (RGO) is a high surface area, conductive substrate with good electron shuttling capability
1. Hodes, G., Manassen, J, J.Electrochem.Sci., 1980
Synthesis
Synthetic Steps:1. Complexation of Cu+ with graphene oxide (GO)2. Disproportionation of Cu+ to Cu2+ and Cu0
3. Wash via centrifugation to remove dissolved Cu2+
4. Reduce GO-Cu0 composite to form RGO-Cu0 5. Add binder and blade onto substrate6. Immerse in polysulfide for conversion of Cu0 to Cu2S
RGO-Cu2SElectrode
Cu
S
Characterization
•Good coverage of RGO with Cu2S is observed•Unique characteristics of RGO generate 3-D macrostructure
-1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2
-40
-30
-20
-10
0
10
20
30
Cur
rent
Den
sity
(m
A/c
m2 )
Voltage (V vs. SCE)
Platinum RGO-Cu
2S
1M Na2S
1M S
-1.0 -0.8 -0.6 -0.4 -0.2 0.0
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Cu
rre
nt
De
nsi
ty (
mA
/cm
2 )
Voltage (V vs. SCE)
Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
Platinum
0.1M Na2S
0.1M S
-1.0 -0.8 -0.6 -0.4 -0.2 0.0-10
-8
-6
-4
-2
0
2
4
6
8
Cu
rre
nt
De
nsi
ty (
mA
/cm
2 )
Voltage (V vs. SCE)
Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
RGO-Cu2S
0.1M Na2S
0.1M S
C D
BA
0 200 400 600 800 1000 1200
0
100
200
300
400
500
Platinum
Z''
(oh
m)
Z' (ohm)
8 10 12 14
0.25
0.50
0.75
1.00
RGO-Cu2S
Z''
(ohm
)
Z' (ohm)
Electrochemical Response
•Pt shows irreversibility and sluggish kinetics with high Rct
•RGO-Cu2S reversible response with Nerstian shifts in CV and low Rct corresponding to Jo = 16 mA/cm2
Photoelectrochemical Response
Superior electrochemical response with good substrate contact led to fully regenerative efficiency of 4.4%
Summary
•Anchored Cu0 nanoparticles on graphene oxide via disproportionation of Cu+ in ethanol to generate RGO-Cu2S composite
•RGO-Cu2S composite exhibits superior regenerative redox activity with polysulfide without corrosion
•High exchange current density leads to lower polarization of counter electrode and thus higher fill factor and maximum power of the quantum dot solar cell
Thank You!
This work can be found in the Journal of Physical Chemistry Letters
J. Phys. Chem. Lett., 2011, 2 (19), pp 2453–2460DOI: 10.1021/jz201064k
More information on the Kamat Research Group can be found at:www.kamatlab.com