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Presentación de PowerPoint€¦ · · 2017-09-19electrode measured with Cu2+ ISME and antimony...
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Contact: Dániel Filotás Tel: +36 70 316 5587; [email protected] Acknowledgements: D. Filotás* ,a,c , T. Nagy b , L. Nagy a,c , Peter Mizsey b , G. Nagy a,c a.) Szentágothai J. Research Center, University of Pécs, 7624, Ifjúság u. 20, Pécs, Hungary b.) Department of Chemical and Environmental Process Engineering, Budapest University of Technology and Economics. Faculty of Chemical Technology and Biotechnology, 1111 Budapest, Gellért tér 4, Hungary c.) Department of General and Physical Chemistry, Faculty of Sciences, University of Pécs, 7624, Ifjúság u. 6 Pécs, Hungary SECM and spectroscopic investigation of unwanted activity changes of metal electrodes observed during electrochemical CO 2 reduction 8.4 8.5 8.6 8.7 8.9 9.0 9.1 pH 2D pH scan above the Cu electrode after polarization at -0.5 V for 10 minutes 8.4 8.55 8.7 8.85 0 250 500 750 pH d [mm] Approaching pH curves above the Cu electrode after polarization at -0.5 V for 10 minutes in KHCO3 CO 2 , nH + CH 4 CH 3 OH HCOOH HCHO … ne - Sb electrode Cu electrode -1.5 -1.0 -0.5 0.0 -1.5x10 -4 -1.0x10 -4 -5.0x10 -5 0.0 i [A] E [V] MEA MEA+CO 2 Cathodic polarization curves of the nickel electrode in 30% MEA solution black: pure solution, red: saturated with CO 2 4.7 4.8 4.9 5.0 5.1 -loga Cu 2+ 8.25 8.5 8.75 9.0 9.25 9.5 pH Distribution of Cu 2+ (A) and pH (B) above the copper electrode measured with Cu 2+ ISME and antimony microelectrodes after 30 minute exposure to 30% MEA solution. -1.5 -1.0 -0.5 0.0 -0.004 -0.003 -0.002 -0.001 0.000 MEA+CO 2 MEA i [A] E [V] Cu Cathodic polarization curves of the copper electrode in 30% MEA solution Vertical approaching curves with amperometric SECM. The tip was 25 um Pt, the sample is nickel in 30% MEA 0.1 M KCl, 1.25 mM Ferrocenemethanol. The Nickel specimen was polarized at different potentials whereas the tip was approaching its surface. The probe was biased at 600 mV. It is getting generally accepted that present level carbon dioxide emission can result in serious changes of the climate of our planet. Unfortunately the alternative zero CO 2 emission sources can provide only fractions of the energy needed. Therefore the complete replacement of the thermoelectric power plants in the near future has no reality. Another solution for this global problem can be the “recirculation” of the CO 2 , the unwanted byproduct of energy production. In this work, electrochemical reduction experiments are carried out in homemade cells supplied different metal electrodes. Electrolytes containing carbon dioxide absorbing components like monoethanolamine (MEA) or KHCO 3 , KOH, and K 2 CO 3 solutions are used. Parallel to the electrochemical measurements the metal components originated from the possible degradation of the electrodematerials in the electrolyte were checked with atomic absorption methods for getting better insight to the nature of the electrode passivation. This contribution attempts to compare the behavior of different electrode materials (copper, nickel and their alloys) in CO 2 capturing media, and investigate of the products of the electrolysis using Scanning Electrochemical Microscopy (SECM), Atomic Absorption Spectroscopy (AAS) and other spectroscopic techniques. The conversion of carbon-dioxide to resuable fuel is one of the greatest challanges of the century. The electrochemical CO 2 reduction has the advantage of the possibility to carry out the conversion in the capturing media broad-scale used in thermoelectric industries. In order to achieve efficient conversion, the selection of suitable electrode material electrode materials is crucial. Nickel and copper have catalytic effect on CO 2 reduction and their applicability in different media is tested with conventional electrochemical methods, SECM and AAS techniques. The detection of the products of the reduction can be performed with SECM and gas chromatography. The new reactor presented enhances the collection of gasous and dissolved products for analysis. Electrolyte Basic solution/ppm After CV/ppm After CV and Absorbed CO 2 /ppm KOH Under LML 1.345 3.554 KOH + KCl Under LML 1.117 2.981 KHCO 3 Under LML 0.065 0.073 Na 2 CO 3 Under LML 0.022 0.031 30% MEA Under LML 6.769 11.778 Absorbed CO 2 mg AAS measured Cu/ppm Corrosion factor 0 0.202 - 100 2.837 0.142 170 4.136 0.122 400 8.489 0.106 507 12.553 0.125 -1.0 -0.5 0.0 0.5 1.0 -10 -9 -8 -7 -6 -5 -4 logi Cu in KCl Ni in KCl Cu in MEA Ni in MEA E [V] 0 50 100 150 200 250 300 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 mV - 100 mV - 600 mV - 700 mV i/i lim d [m] Table 1. Measured Cu in different electrolytes CO 2 absorbed for 3 minute purging The corrosion factor (AAS measured mg Cu/mgCO 2 in 5 ml electrolyte) is determined in 30 % MEA depending on the CO 2 content. It can be said that above 170 mg absorbed CO 2 /5 ml MEA the corrosion factor can be regarded independent of the absorbed amount of CO 2 This feature of the system is promising considering the perspective industrial applications of the electrochemical reduction of CO 2 in MEA. AAS measurements The data of Table 1. indicate the more absorbed CO 2 content of the electrolyte the bigger is the Cu content of the electrolyte. The KHCO 3 and Na 2 CO 3 electrolytes absorb the less CO 2 amount. Considerable good absorbents are the 0.1 M KOH and 0.1 M KOH + 0.1M KCl solutions beside the 30% MEA. Table 2. Measured Cu in 30% MEA The copper content of the electrolytes were measured with PerkinElmer PinAAcle 900T atomic absorption analysis at l=324.75 nm, using acetylene-air flame (air 10 L/min, acethylene 2.5 L/min). The calibration was linear in the 0 - 5 ppm concentration range: y=0.0664x+ 0.0006 (R 2 =0.9991). Conclusions Introduction SECM detection of product formation Tafel plot of Cu and Ni electrodes in different electrolytes Corrosion study of Ni and Cu electrodes One of the most often used CO 2 capture absorbent in industrial scale is the aqueous solution of monoethanolamine (MEA) Detection of products with gas chromatography Cathodic polarization curves of Ni and Cu electrodes 2 3 4 5 6 0 5000 10000 15000 20000 25000 30000 Intensity [V] t [min] MEA MEA+1ppm MeOH Reaction at -1.4V for 2 hours Novel reactor facilitates to collect the gasous products Detection of methanol in the reaction medium The local changes of the electrode where the conversion takes place can be monitored SECM with high resolution and sensitivity
Transcript of Presentación de PowerPoint€¦ · · 2017-09-19electrode measured with Cu2+ ISME and antimony...
Contact: Dániel Filotás
Tel: +36 70 316 5587; [email protected]
Acknowledgements:
D. Filotás*,a,c, T. Nagyb, L. Nagya,c, Peter Mizseyb, G. Nagya,c
a.) Szentágothai J. Research Center, University of Pécs, 7624, Ifjúság u. 20, Pécs, Hungary
b.) Department of Chemical and Environmental Process Engineering, Budapest University of Technology and Economics. Faculty of
Chemical Technology and Biotechnology, 1111 Budapest, Gellért tér 4, Hungary
c.) Department of General and Physical Chemistry, Faculty of Sciences, University of Pécs, 7624, Ifjúság u. 6 Pécs, Hungary
SECM and spectroscopic investigation of unwanted
activity changes of metal electrodes observed during
electrochemical CO2 reduction
8.4
8.5
8.6
8.7
8.9
9.0
9.1
pH
2D pH scan above the Cu electrode after polarization at -0.5 V for 10 minutes
8.4
8.55
8.7
8.85
0 250 500 750
pH
d [mm]
Approaching pH curves above the Cu electrode after polarization at -0.5 V for 10 minutes in KHCO3
CO2
, nH+
CH4
CH3OH
HCOOH
HCHO
…
ne-
Sb electrode
Cu electrode
-1.5 -1.0 -0.5 0.0-1.5x10
-4
-1.0x10-4
-5.0x10-5
0.0
i [A
]
E [V]
MEA
MEA+CO2
Cathodic polarization curves of the nickel electrode in 30% MEA solution black: pure solution, red: saturated with CO2
4.7 4.8 4.9 5.0 5.1
-logaCu2+
8.25 8.5 8.75 9.0 9.25 9.5
pH
Distribution of Cu2+ (A) and pH (B) above the copper electrode measured with Cu2+ ISME and antimony microelectrodes after 30 minute exposure to 30% MEA solution.
-1.5 -1.0 -0.5 0.0-0.004
-0.003
-0.002
-0.001
0.000
MEA+CO2
MEA
i [A
]
E [V]
Cu
Cathodic polarization curves of the copper electrode in 30% MEA solution
Vertical approaching curves with amperometric SECM. The tip was 25 um Pt, the sample is nickel in 30% MEA 0.1 M KCl, 1.25 mM Ferrocenemethanol. The Nickel specimen was polarized at different potentials whereas the tip was approaching its surface. The probe was biased at 600 mV.
It is getting generally accepted that present level carbon dioxide emission can result in serious changes of the climate of our planet. Unfortunately the alternative zero CO2 emission sources can provide only fractions of the energy needed. Therefore the complete replacement of the thermoelectric power plants in the near future has no reality. Another solution for this global problem can be the “recirculation” of the CO2, the unwanted byproduct of energy production.
In this work, electrochemical reduction experiments are carried out in homemade cells supplied different metal electrodes. Electrolytes containing carbon dioxide absorbing components like monoethanolamine (MEA) or KHCO3, KOH, and K2CO3 solutions are used. Parallel to the electrochemical measurements the metal components originated from the possible degradation of the electrodematerials in the electrolyte were checked with atomic absorption methods for getting better insight to the nature of the electrode passivation. This contribution attempts to compare the behavior of different electrode materials (copper, nickel and their alloys) in CO2 capturing media, and investigate of the products of the electrolysis using Scanning Electrochemical Microscopy (SECM), Atomic Absorption Spectroscopy (AAS) and other spectroscopic techniques.
The conversion of carbon-dioxide to resuable fuel is one of the greatest challanges of the century. The electrochemical CO2 reduction has the advantage of the possibility to carry out the conversion in the capturing media broad-scale used in thermoelectric industries. In order to achieve efficient conversion, the selection of suitable electrode material electrode materials is crucial. Nickel and copper have catalytic effect on CO2 reduction and their applicability in different media is tested with conventional electrochemical methods, SECM and AAS techniques. The detection of the products of the reduction can be performed with SECM and gas chromatography. The new reactor presented enhances the collection of gasous and dissolved products for analysis.
Electrolyte Basic
solution/ppm After CV/ppm After CV
and Absorbed
CO2/ppm
KOH Under LML 1.345 3.554
KOH + KCl Under LML 1.117 2.981
KHCO3 Under LML 0.065 0.073
Na2CO3 Under LML 0.022 0.031
30% MEA Under LML 6.769 11.778
Absorbed
CO2 mg AAS measured
Cu/ppm
Corrosion
factor
0 0.202 -
100 2.837 0.142
170 4.136 0.122
400 8.489 0.106
507 12.553 0.125
-1.0 -0.5 0.0 0.5 1.0-10
-9
-8
-7
-6
-5
-4
logi
Cu in KCl
Ni in KCl
Cu in MEA
Ni in MEA
E [V]
0 50 100 150 200 250 3000.5
1.0
1.5
2.0
2.5
3.0
3.5
0 mV
- 100 mV
- 600 mV
- 700 mV
i/i li
m
d [m]
Table 1. Measured Cu in different electrolytes CO2 absorbed for 3 minute purging
The corrosion factor (AAS measured mg Cu/mgCO2 in 5 ml electrolyte) is determined in 30 % MEA depending on the CO2 content. It can be said that above 170 mg absorbed CO2/5 ml MEA the corrosion factor can be regarded independent of the absorbed amount of CO2 This feature of the system is promising considering the perspective industrial applications of the electrochemical reduction of CO2 in MEA.
AAS measurements
The data of Table 1. indicate the more absorbed CO2 content of the electrolyte the bigger is the Cu content of the electrolyte. The KHCO3 and Na2CO3 electrolytes absorb the less CO2 amount. Considerable good absorbents are the 0.1 M KOH and 0.1 M KOH + 0.1M KCl solutions beside the 30% MEA.
Table 2. Measured Cu in 30% MEA
The copper content of the electrolytes were measured with PerkinElmer PinAAcle 900T atomic absorption analysis at l=324.75 nm, using acetylene-air flame (air 10 L/min, acethylene 2.5 L/min). The calibration was linear in the 0 - 5 ppm concentration range: y=0.0664x+ 0.0006 (R2=0.9991).
Conclusions
Introduction
SECM detection of product formation
Tafel plot of Cu and Ni electrodes in different electrolytes
Corrosion study of Ni and Cu electrodes
One of the most often used CO2 capture absorbent in industrial scale is the aqueous solution of monoethanolamine (MEA)
Detection of products with gas chromatography
Cathodic polarization curves of Ni and Cu electrodes
2 3 4 5 60
5000
10000
15000
20000
25000
30000
Inte
nsi
ty [
V]
t [min]
MEA
MEA+1ppm MeOH
Reaction at -1.4V for 2 hours
Novel reactor facilitates to collect the gasous products Detection of methanol in the reaction medium
The local changes of the electrode where the conversion takes place can be monitored SECM with high resolution and sensitivity
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