Electrochemical application on boron-doped diamond...

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Electrochemical application on boron-doped diamond electrodes Yasuaki Einaga Department of Chemistry Keio University Japan

Transcript of Electrochemical application on boron-doped diamond...

Page 1: Electrochemical application on boron-doped diamond …phantomsfoundation.com/1AND2DM/2020/Presentations/...Electrochemical application on boron-doped diamond electrodes Yasuaki Einaga

Electrochemical application on boron-doped diamond electrodes

Yasuaki EinagaDepartment of Chemistry

Keio UniversityJapan

Page 2: Electrochemical application on boron-doped diamond …phantomsfoundation.com/1AND2DM/2020/Presentations/...Electrochemical application on boron-doped diamond electrodes Yasuaki Einaga

Boron concentration carbon density in diamond = 1.76×1023

boron solubility into diamond ≥ 1.4×1022

Boron-doped Diamond (BDD)

~ 1018 1019 1020 1021 1022No doping (cm-3)

0.01 % 0.1 % 1 %0B/C

[B]

Insulator Semiconductor

Diamond Electrodes

Metal 10-2Ωcm

Many studies

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Electrochemical Properties of Boron-doped Diamond (BDD) Electrodes

Wide potential window(-1.2~2.0V)

Low background current(100 nAcm-2)

Physically and chemically stable

Oxygen evolutionHydrogen evolution

Generation of active species (・OH etc)

Au

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Development of diamond electrodes (2000~)

Diamond Electrodes

Heavy metals, Chlorine, etc

Glucose, Uric acid, Oxalic acid, Cancer marker, Neurotransmitter

Environmental sensors

Bio, Medical sensors

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1.3 V

0

0.2

0.4

0.6

0.8

1

0.5 1 1.5

Potential (V vs. Ag/AgCl)

Glassy Carbon

Pt

Au

Diamond electrodes

Cur

rent

Den

sity

(mA/

cm2 )

1.3 V

0

0.2

0.4

0.6

0.8

1

0.5 1 1.5

Potential (V vs. Ag/AgCl)

Glassy Carbon

Pt

Au

Diamond electrodes

Cur

rent

Den

sity

(mA/

cm2 )

Detection of free chlorine

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Cur

rent

Den

sity

(mA

/cm2 )

120100806040200

Concentration (mg/l)

Calibration curve1.2

1.0

0.8

0.6

0.4

0.2

0.0

Cur

rent

Den

sity

(mA

/cm2 )

120100806040200

Concentration (mg/l)

Calibration curve

6

8

10

12

14

Time (min)

Cur

rent

(nA)

0 5 10

6

8

10

12

14

Time (min)

Cur

rent

(nA)

0 5 10

100

80

60

40

20

0C

urre

nt D

ensi

ty (m

A/c

m2 )2.01.51.00.50.0

Concentration (mg/L)

Even in low concentration region (0-2ppm), the detection was possible.

Calibration curve

6ClO- + 3H2O 3ClO3- + Cl- + 6H+ + 3/2O2 + 6e-

Hypochlorite ion

J. Electroanal. Chem., 612, 29 (2008).

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Prototype of Residual Chlorine Monitor (2018)

Functional Water Foundation

Press release: Aug. 30th, 2018

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In China (2019)Institute for Electronics and Information Technology in Tianjin, Tsinghua University清华大学天津电子信息研究院 ・ HORIBA(堀場製作所)

Cd detection in rice

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- High current density- High sensitivity - Steady-state current response- Negligible effect of IR dropthree dimensional diffusion

< Remarkable properties of microelectrodes >

5µm

Electrochemical analysis by BDD microelectrodes

Next generation electrodes for sensor

In vivo detection

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Simultaneous detection of phermacokineticsRecent Topics

Bumetanideloop diuretic drug[Uses] edema, neonatal seizures[Side Effects] hearing loss

Amplifier

Potentiostat

Guinea pig

Cochlea

Glass Microelectrode

syringe

Diamond Microelectrode

Drug concentration(Diamond microelectrode)

Hearing ability(Glass microelectrode)

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Hearing loss

Bumetanideinjection30 mg/kg

BumetanideSampling frequency0.2 Hz

EPSampling frequency40 Hz

Level of hearingEndocochlear potential : EP

(mV)

Bum

etan

ide

(µM

)

Nature Biomed. Eng. 1, 654 (2017).Science 359, 1287 (2018).[Highlight]

Real time measurement

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Development of diamond electrodes

Diamond ElectrodesFundamental

Study

Heavy metals, Chlorine, etc

Glucose, Uric acid, Oxalic acid, Cancer marker, Neurotransmitter

Environmental sensors

Bio, Medical sensors

2012~

Waste water treatment

Ozone generation

Electrochemical organic synthesis

Improvement of environment

CO2 reduction2014~

(2011~)

Electrochemiluminescence(ECL)

2016~ New!!

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• Fuel

• Plastics

CO2 CxHyOz

Surface

e-, H+

CO2 reduction using BDD electrodes

Reduction

CO2 Reduction

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Electrochemical reduction of CO2by conventional electrodes (1980~)

1) CO2 + 2H+ + 2e- → CO + H2O2) CO2 + 2H+ + e- → HCOOH3) CO2 + 6H+ + 6e- → CH3OH + H2O4) CO2 + 8H+ + 8e- → CH4 + 2H2O5) 2H+ + 2e- → H2 in MeOH

41 atm25 oC

CO2

Electrolyte

e-

CO2

ProductsOxidation

Power source H2

Hydrocarbon

HCOOH

J. Electrochem. Soc., 141, 2097 (1994); J. Electroanal. Chem., 404, 299 (1996).

Cu electrodesin H2O1-60 atm25 oC

Low efficiencyHigh pressure Low stability

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Electrochemical Properties of Boron-doped Diamond (BDD) Electrodes

Wide potential window(-1.2~2.0V)

Low background current(100 nAcm-2)

Physically and chemically stable

Oxygen evolution

Generation of active species (・OH etc)

Au

Supresshydrogen evolution !

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Reduction of CO2Room TemperatureAmbient pressure

Angew. Chem. Int. Ed., 53, 871 (2014).Faradaic efficiency / %

Elec

trode

mat

eria

ls

Formaldehyde (HCHO) HCOOH

HCOOHHCHO

HCOOCH3

HCOOCH3 CO

CO CH4

H2

H2

H2

H2

HCOOCH3

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Recent trial for CO2 reduction

2. Produce more valuable compounds

1. 100% Faradaic efficiency

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Catholyte: 0.5 M KCl aq.Anolyte: 1.0 M KOH aq.

Formic acid production

Flow cell

CO2 + 2H+ + 2e− ➝ HCOOH(Current density: 2, 5, 10, 20 mA cm−2)

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Flow rate(mL min−1)

FE ofHCOOH (%)

FE of H2(%)

Total FE (%)

20 35 41 76

50 85 8.6 95

100 91 3.6 95

200 95 4.1 100

500 88 8.1 99

Dependence of electrolyte flow rate

Faradaic efficiency @ 2 mA cm−2

100

80

60

40

20

0

Fara

daic

Effi

cien

cy (%

)

5004003002001000Flow Rate (mL min-1)

HCOOH H2

Faradaic efficiency of HCOOH increased up to 95% with increasing flow rate.

⇒ Progress of CO2 mass-transport

Angew. Chem. Int. Ed., 57, 2639 (2018).

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Recent trial for CO2 reduction

2. Produce more valuable compounds(To control of the production)

1. 100% Faradaic efficiency

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Cu nanoparticleBDD electrode

CO2 ?aqueoussolution

C2/C3 compounds were produced!

C2H5OH (Ethanol)CH3CHO (Acetaldehyde)(CH3)2CO (Acetone)

Anolyte: KOH 0.5 MCatholyte: KCl 0.5 M

Electrochim. Acta., 266, 414 (2018).

(1) Cu-modified BDD electrodes

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Examples :1. MEA (Monoethanolamine) 2. EAE (N‐Ethylamino ethanol)3. DEA (Diethanolamine), 

4.   Ammonia solution [high  loading capacity : 1.76 kg CO2/kg NH3

MEA = 0.55‐0.58 kg CO2/kg MEA ] 

Mani, F. et al. Green. Chem. 2006, 8, 995‐1000

NH3(aq) +  CO2                                                            ?Reduction on BDD

Purpose : 

(2) In Amine Solution

Amine solutions are used for CO2 absorber….

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NH3 + CO2 + H2O ⇄ NH4+ + HCO3

-

HCO3- + 5H2O + 6e- ⇄ CH3OH + 7OH-

Methanol is the main product

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pH 7.5 - 9.0 : HCO3- is dominant

Zhong, H. et al. J. Phys. Chem. C., 2015, 119, 55-61.

CO2 (aq) + H2O (l) H+(aq) + HCO3

-(aq) pK1 = 6.35

H+(aq) + HCO3

-(aq) 2H+

(aq) + CO32-

(aq) pK2 = 10.33

CO2 HCO3- CO3

2-

pH is also an important factor for the production!!

RSC Adv., 6, 102214 (2016).

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(3) Electrolyte

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Cation dependence

Li, Na << K, Rb, CsFaradaic efficiency for HCOOH production

100

80

60

40

20

0

Fara

daic

effi

cien

cy (%

)

LiCl NaCl KCl RbCl CsCl

HCOOH H2

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Buffer effects of alkali cation

26

Singh, M. R. et al. J. Am. Chem. Soc. 2016, 138, 13006-13012.CO2 reduction by Ag electrodes

pH near cathode

Large cation ⇒ High buffering effect

K+, Rb+, Cs+ : pH (near cathode) is stable

pH increase (near cathode)CO2 + 2H+ + 2e– → CO + H2O2H+ + 2e− → H2

[M+(H2O)n] ⇄ [MOH(H2O)n–1] + H+Buffering effect by Hydrated cations

CO2 concentration near cathode

High efficiency for HCOOH production K, Rb, Cs

K+, Rb+, Cs+: pH is stable

CO2 concentration is high (CO2 + H2O ← H+ + HCO3

−)

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Anion dependence

NO3‒ + H2O + 2e‒

→ NO2‒ + 2OH‒

HCOOHproduction

COproduction

ChemistrySelect, 3, 10209 (2018).

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(–2.1 V vs. Ag/AgCl)

80

60

40

20

0

Fara

daic

effi

cien

cy (%

)

KClO4 KCl

CO HCOOH H2

KClO4 KCl

J. Am. Chem. Soc., 141, 7414 (2019).

CO production in KClO4

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CO2+e- ꞏCO2

-(ad)

ꞏCO2-(ad) CO + CO3

2-+CO2, +e- ꞏCO2

-(ad) HCOO-

(ad)+H+, +e-

Electrode

CO2•‒

Electrode

CO2•‒

?

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in-situ ATR-IR

BDDSi

IR beam IR detector

CxHyOzCO2

Abso

rban

ce

1750 1700 1650 1600 1550Wavenumber (cm-1)

KClO4

KCl

0.003

KClAb

sorb

ance

1800 1700 1600 1500 1400 1300Wavenumber (cm-1)

0.004

30 min

5 min

Abso

rban

ce

1800 1700 1600 1500 1400 1300Wavenumber (cm-1)

0.004

30 min

5 min

KClO4

Intermediate

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Measurement by 13C BDD

Interaction between intermedeates (CO2•‒) and BDD electrodes are different.

CC

CO2•‒

⇒ COKClO4

CC

CO2•‒

⇒ HCOOHKCl

J. Am. Chem. Soc., 141, 7414 (2019).

CO2•‒