2

2

( , ; )

( , ; )

D S pt

D S pt

ECD: Spelch (topics specifically addressed in talk)

1) PREMISE: WHY IN SITU SPECTROELECTROCHEMISTRY

FOR ELECTROCHEMICAL MATERIALS-SCIENCE PROBLEMS?

CN¯-related electrochemical instabilities in Au-alloy electrodeposition

2) THE SURPRISING INTERFACIAL STORY OF CN¯ RELEASED FROM

CYANOCOMPLEXES DURING ELECTRODEPOSITION OF Au AND Au-ALLOYS

(2.1) Speciation; (2.2) Dynamics; (2.3) Coadsorption; (2.4) Reactivity

3) BEYOND CN¯: CN¯-FREE Au ECD BATHS

4) Cu-INTERCONNECTS (VIA FILLING)

(4.1) Suppressor (PEG); (4.2) Accelerator (SPS); 4.3) Levellers; 4.4) The full package

5) ECD FROM RTIL

6) MONITORING ECD OF METAL/OXIDE COMPOSITES

7) ACTIVITY OF ELECTRODEPOSITED ELECTROCATALYSTS

ECD: contents

1) Spelch: Section E of present seminar

2) Materials for supercapacitors: Section D of present seminar

3) ECD from RTIL: see Section E5

4) ECD from non-aqueous electrolytes (different from RTIL)

5) Cu-damascene: Section E4

5) DIB (strictly related) [415, 388, 284], WASCOM ’12 [368, 372], Ripple [357, 370]

6) Non-metals, non-PPy:

(i) NiO/YSZ [308]; (ii) Y2O3/CoO, Y2O3/Au [323]; (iii) PANI/CNT [343];

(iv) montmorillonite+epoxy (electrophoresis) [320]; (v) DLC [394];

(vi) hydroxyapatite+heparine@Ti [395]

7) Archaeometallurgy:

(i) recostruction of Ag coins [409]; (ii) treatment of bronze disease [315,392];

(iii) ancient forgeries (Parabita) [248, 382]

8) Metal-based composites:

(i) Au/Dy2O3 from RTIL [386]; (ii) Au/Y2O3; (iii) Ni/ceria [376];

(iv) filling of porous ceramic [153]; (v) Au/B4C [124, 146]

9) Magnetic field effects (on 2D and 3D mass transport) [266, 282, 298, 329]

10)Semiconductors: (i) GaAs [219]; (ii) InAs [188]; (iii) ZnTe [140, 141]

11)Au alloys: more recent work Section E

12)Alloys: older work (NiP, NiP/Sn, CoPt, CoPd, ZnMn, CuSb)

13)ACD: older work on NiP, NiP-based composites, CoP

[1, 5, 69, 72, 75, 83, 85, 102, 108, 119, 125, 126, 128, 144, 155, 163, 164]

ECD: Spelch (topics not covered in talk)

OTHER ECD-SPELCH TOPICS THAT HAVE BEEN OMITTED IN THIS TALK

1) ex-situ SPEM for morphochemical studies related to DIB-modelling

2) mCT for the electrochemical restoration of corroded ancient Ag coins

3) Studies of Ag ECD from non-aqueous (ACN) and mixed (ACN+H2O) solutions

(SERS, SHG))

4) Study of ECD intermediates (Ni(OH)2,ads, role of H3BO3 in Co ECD) (Raman)

5) TR studies of UPD

6) Cu ECD in the presence of self-assembling systems (SERS and SFG)

7) Raman-based studies of incorporation of organics into ECD layers.

ECD: methods spelch

1) Metastable structures in ECD alloys:

(i) supersaturated solid solutions; (ii) intermetrallics TD-ly stable at high T;

(iii) metallic glasses

2) Mass-transport and fluid-dynamics (alloys and composites)

3) Morphology of electrodeposited metals and alloys

4) ECD for functional films: (i) magnetic, (ii) corrosion resistance; (iii) wear resistance

Non-ECD studies in materials electrochemistry

1) Hardmetals (WC-Co type): corrosion and recovery of raw materials

(i) corrosion of hardmetals and binders [181, 199, 200, 213, 225]

(electrochemistry and structure); (ii) Spelch during corrosion of HM

(FTIR [208], SFG [427, 302, 259], ERS [259]); (iii) SPEM [302])

2) Corrosion:

(i) Petrochemical [426], (ii) High-T aqueous and molten salts [364, 367];

(iii) Cu/S [358]; (iv) dental implants [268,337]; (v) Rebar by Spelch

(Raman [244], FTIR [255], SHG [277]); (vi) steel/C-fibres [169];

(vii) Ag [224, 228]; (viii) tribocorrosion [167, 193, 194, 197, 206]

3) Archaeometallurgy

(i) ancient forgeries in coins [258]; (ii) incluse coins [220]

4) Adsorption at metal surfaces (by Spelch)

aqueous solutions - (i) FTIR+Raman coadsorption CN¯+org @Ag(111) [218]:

(ii) SFG/DFG adsorption and coadsorption:

CN¯ @Au(xyz) [230], @Au-alloys [231], coads. CN¯+org @Au(xyz) [212, 232]

(iii) 2D-SFG org. @Cu(poly) [269]

(iv) TR: Cl¯ @Au(111) [306]

(v) Raman org. @Au(poly) [190]

RTIL - [BMP][TFSA] [318]

5) Microfabrication (related to Cu-damascene):

etching of CoSi [287], corrosion of Cu ECD by volatile organics [285]

1) PREMISE: WHY IN SITU SPECTROELECTROCHEMISTRY

FOR ELECTROCHEMICAL MATERIALS-SCIENCE PROBLEMS?

CN¯-related electrochemical instabilities in Au-alloy electrodeposition

[115] (1999)

hi-Aulo-Au

FREE-CN¯ Au-Cu BATH instabilities

[115] (1999)

Au-Cu alloy

Au-Cu/B4C

composite

Morphochemical impact of instabilities in Au-Cu ECD

Cd2+ 1.0 g/L

Cd2+ 0.3 g/L

[148] (2001)

2 mA cm-2

FREE-CN¯ Au-Cu-Cd BATH instabilities mitigated

20 mA cm-2

10 mA cm-2

with B4C

[135] (2000), [137] (2000)

See Section E2.3: “UPD-DRIVEN” 18 kt Au-Cu

CYANOCOMPLEX Au-Cu BATH instabilities suppressed

Au(CN)2¯

CuCN, Cu(CN)2¯, Cu(CN)32-

equil

ECD

ECD from

majority species

ECD from

minority species:

cathode passivation

Au(CN)2¯

Cd(CN)42-

CuCN, Cu(CN)2¯, Cu(CN)32-

electrochemical

nobility

“Electroactivity gap” filled.

Cd2+ 1.0 g/L

Cd2+ 0.3 g/L

Au-Cu+KCN

+ UPD role of Cd

Au(CN)2¯

Cu(II)-EDTA

Kstab[Cu(II)-EDTA]>>Kstab[Cu(II)-CN¯] no impact of CN¯ release

Au(I), Cu(I), KCN

Au(I), Cu(II), EDTA

Hysteretic behaviour suppressed

2) THE SURPRISING INTERFACIAL STORY OF CN¯ RELEASED FROM

CYANOCOMPLEXES DURING ELECTRODEPOSITION OF Au AND Au-ALLOYS

2.1) Speciation

2.2) Dynamics

2.3) Coadsorption

2.4) Reactivity

2.1) Speciation

SETTING THE SCENE: vibrational spectroscopies of adsorbed CN¯ during ECD()

[176] (2002) Raman: strong enhancement from growth features (SERS)

ECD from Au(CN)2¯

Au-NC¯Au-HAu-CN¯Au-CNO¯

Au(CN)2¯

Intramolecular bands

A range of different types of surface CN¯

n(Au-C)

d(Au-CN)

n(Au-N)

Extramolecular bands

FTIR: more representative of average cathode conditions & film formation (2-state probe)

ECD from Au(CN)2¯[214] (2004)

free CN¯

CN¯ads

Au(CN)2¯

AuCN

vs. SERS hot-spots

Formation of (intermediate) AuCN films during electroreduction

Sum Frequency Generation (SFG) Spectroscopy

2nd-order non-linear optical process:

2 laser beams ωVIS e ωIR interact, yielding:

This process is forbidden

in centro-symmetric media

Extreme interface sensitivity

(symmetry breaking at the interface)

ωSFG = ωVIS + ωIR

ωDFG = ωVIS ω2IR

SFG spectroscopy - optics

SFG: more representative of average cathode conditions (1-state probe)

(2) (2) (2)

,tot zzz res NR

SFG/DFG intensity:

Components of tot

SFG/DFG spectroscopy

Models and quantitative analysis2

2 2(2) (2) (2)

, , ,xyz tot xyz zzz tot zzz tot zzz

xyz

I P P const

Resonant part res: vibrational state

and orientation of adsorbate

(2)

/

( )

[ ( )]res

o SFG DFG

A V

V i

n n

Non-resonant part NR: electronic

structure of the metallic substrate (2) ( )NR IRa V i n

Optical set-up optimisation routines set a limit on physical

meaning of parameters (absolute values of I):

(i) Purely vibrational parameters: no, , A(V)/Amax;

(ii) Purely electronic parameter: Df=fSFG-fDFG;

(iii) Interference parameter: c=2·|r|·|NR|/[|r|2·|NR|2].

VIS: doubled YAG, 532 nm

IR:

OPO-SFG Benchtop Optical Parametric Oscillator (OPO), 2.5÷10 μm

CLIO-FEL-SFG FEL-IR: 3.5÷50 μm

SFG/DFG spectroscopy - Facilities

Electrodeposition Au(CN)2¯ and Au(CN)4¯

0.1M NaClO4, 25mM

KAu(CN)2

0.1M NaClO4, 25mM KAu(CN)4

SFG: more representative of average cathode conditions (1-state probe)

[260] (2004)

Impact of type of cyanocomplex metal precursor

Electrodeposition: Au(CN)2¯ and Au(CN)4¯ quantitative analysis – no,

Differences in Stark shift and between Au(I) and

Au(III) suggest different adsorption sites for CN¯

values measured during ECD are larger by a factor

of 2÷3 than for static electrodes

Stark shift

Au(CN)2¯: 35.89±1.32 V-1 cm-1

Au(CN)4¯: 32.29±1.59 V-1 cm-1

Peak half-width

Not affected by potential

Au(CN)2¯: 16.15±2.6 cm-1

Au(CN)4¯: 25.33±3.1 cm-1

Electrodeposition: Au(CN)2¯ and Au(CN)4¯quantitative analysis – A, fNR

Discontinuity with potential visible in A and fNR

change of electrodeposition mechanism: case of Au(I):

low cat: Au(CN)2¯ AuCNads + CN¯, AuCNads + e¯ Au + CN¯

high cat: Au(CN)2¯ + e¯ Au + CN¯

Au(I) vs. Au(III): similar values of A, different of fNR for V<-1 V

[215] (2004) Au-Ag

Single-phase alloy, but 2 different adsorption sites

AuAu-Ag

Au-ALLOYS Single-phase deposits of composition

ranging from 13% to 75% Au

-700 mV

-1100 mV

-1300 mV

Different adsorption sites

in alloy ECD

[184] (2003) Au-Sn

2.2) Dynamics

2.2.1) Analysis of SERS time series

2.2.2) SERS during pulse plating

2.2.3) Transient reflectivity

Time-dependent SERS measurements

0 2000 4000 6000 8000 10000

1

2

3

4

5

6

7

8

inte

nsità

se

gn

ale

no

rm.

tempo [s]

CN norm

0 500 1000 1500 2000 2500

0

1000

2000

3000

4000

5000

inte

nsità

se

gn

ale

n [cm-1]

0 2000 4000 6000 8000 10000

200

400

600

800

1000

1200

1400

1600

1800

inte

nsità s

egnale

tempo [s]

B

CN BCNnorm

B

Objectives:-500 mV → 50x

-1000 mV → 10x e 50x

-1600 mV → 10x

2.2.1) Analysis of SERS time series

Typical spectral patterns

0 500 1000 1500 2000 2500

0

1000

2000

3000

4000

5000

inte

nsità

se

gn

ale

n [cm-1]

Extramolecularn(Au-C) ~300 cm-1

n(CN¯ads)

~ 2108 cm-1

0 500 1000 1500 2000 2500

0

200

400

600

800

1000

inte

nsità

se

gn

ale

n [cm-1]

n(CN¯ads)

~ 2075 cm-1

Hydrogenation product of CN¯

0 500 1000 1500 2000 2500

40

60

80

100

120

140

160

180

inte

nsità

se

gn

ale

n[cm-1]

Fluorescence

n(CN¯ads)

~ 2115 cm-1

0 500 1000 1500 2000 2500

50

100

150

200

250

300

inte

nsità

se

gn

ale

n [cm-1]

1381 s

1929 s

2600 s

3046 s

7003 s

Time-dependent trend of fluorescence

-500 mV

-1000 mV

-1600 mV

Micrographic investigation (SEM)

Measurement and modelling of ACF

for I[n(CN¯)] and Ibackgroung

1 2

1 2

( ) exp exp sint t t

ACF t A AT

D D D D

1. 1 relaxation time of auto-correlation

2. T period of the oscillating component

3. 2 oscillation damping time constant

0 100 200 300 400 500 600

-200000

-100000

0

100000

200000

300000

400000

500000Data: Data4_B

Model: nuova

Chi^2 = 781380517.1537

R^2 = 0.83731

P1 487.19904 ±41.70268

P2 13.66599 ±0.03269

P3 1.28551 ±0.04195

P4 114634.63709 ±4935.22437

P5 384833.76325 ±28542.81485

P6 5.89736 ±0.61817

au

toco

rre

lazio

ne

ritardi [s]

acf B 4°

fit acf

Modellisation of coupled dynamics of

morphology and surface composition

2

2

( , ; )

( , ; )

D S pt

D S pt

,

, ,x y

I t x y t dxdy

,

, ,x y

I t x y t dxdy

t ε [0,T]

Dfixed p ; different values of

D

(t)

M*(t)

(t)

2.2.2) SERS during pulse plating [241] (2006)

Femtosecond in situ transient reflectivity measurements.

Ultrafast electronic response controlled by electrochemical processes: corrosion, deposition of metal layers, chemisorption.

Concept of the experimenti) fs monochromatic pump pulseii) delayed (fs-ps range) broadband fs probe pulseiii) detection of reflected probe

2.2.3) Transient reflectivity

Experimental - electrochemistry

WE: Au(111)

Electrolytes:(i) 0.1M NaClO4

(ii) 0.1M NaClO4 + 0.025M KCN

(iii) 0.01M CuSO4 + 0.5M H2SO4

Reflection cell

Thick electrolyte layer (visible pump & probe)

Flexible sample-holder

Experimental - optical set-up

Ti:sapphire FF 780 nm, 500-µJ, 150 fs, 1 kHz repet. rate BS:

0.1÷2 mJ to pump line (possibly through wl-tuning device) incl. delay0.1÷2 mJ to probe line through white-light generation in sapphire plate

Reflected probe analysed by spectrograph

Chopped pump beam allows to measure:

tR

tRtRt

R

R

off

offon

D

DDD

D

,

,,,

Chief highlights of this set-up:- Spectral capability (450÷650 nm) with fixed pump frequency- Tunability of the pump frequency

Transient Reflectivity

In our experiments pump energy at 780 nm: hn1<hnIB

Pump beam excites the e¯ population, collisions thermalise the distribution.

Energy relaxation channels for e¯

Specific relaxation channels can be active at electrochemical interfaces:

"electron-surface" interactions:

surface states, adsorbed molecules, grain boundaries

metal nanoparticles at the interface (nuclei, clusters, crystallites)

subsurface alterations of the metal

lattice

surface

electronliquid

e-s

e-ph

e-e

hn

fit parameters

2D spectra

transients and fits

Typical data structure e.g. Au(111)/NaClO4

Dynamic Model

Pump pulse at win affects electron distribution r(E,t;win)

Broadband probe pulse monitors reflectivity R(t,w), But R=R(e) and e=e(r;D)

Thus:

The evolution of r can be described by the Boltzmann equation:

s"" and ph"" of dynamics

anL

sephe

s

ee ttq

tt

rrrr

qs is the screening length

e-ph denotes the phonon coupling term

e-s accounts for surface contributions

L is the source due to absorption of laser energy

an is the source due to anodic hot electron injection

inin

inDt

R

RDt

ED

twwwwe

wwr,;,,;,

;, DD

D

Integration of Boltzmann eq. and convolution with the DOS yield the transient reflectivity model.

In situ electrochemical experiments

Au(111)/KCN

chemisorption andactive corrosion

@ -0.25VAg/AgCl

Au(111)/KCN

-0.25 VAg/AgCl:

Au(0)-CN¯

0.20 VAg/AgCl:

Au(I)-CN¯

- Changes in dynamic and dispersionbehaviour

- Faster decay with CN¯ - decay rate correlates with applied potential

surface-state scattering effects

set

tk

,r

2.3) Coadsorption

[214] (2004)

Citrate adsorbs anodically from KAu(CN)2-Na3citrate baths

corrosion-driven desorption

(Au dissolves)electrostatically-

controlled

adsorption

O O

R

Supporting electrolyte

MULTILAYERES STRUCTURES RELATED TO CATHODIC PASSIVATION

[185] (2002)

Au

AuCN

Au

w/o Tl+: ECD stops

with Tl+ & low-c.d: ML structures are obtained

with Tl+ & high-c.d. conventional Au is obtained

AuCN

Au

XPS+XRD

Au

AuCN

Au

Inorganic additives

ROLE OF Tl+ at hi-c.d.: “CN¯ hopping” + UPD effects[183] (2002)

passivating form

active process

Au-NC¯

Au-CN¯

FTIR

Au

Tl+-d

Au

Tl+-d

Au

Tl+

Tl+-d

Au

Tl+

Tl+-dAu0

Au

Tl+[185] (2002)Depassivating role of UPD

(e.g. Tl+ & Cu2+ )

COADSORPION OF ADDITIVES (for morphology control)

[184] (2003) Au-Snno 4CP 100 ppm 4CP

20 mm 20 mm

60 mm 20 mm

20 mm 8 mm

Addition of 4CP: Different phases

with different textures,

more compact morphologies

-0.5V

-0.6V

-0.7V

AuSn

AuSn

AuSn2

AuSn4

AuSn

Au5Sn

AuSn

AuSn2

AuSn4

AuSn

Inorganic additives

Anodic: vertical through nitrile, then (CGS) tilts and switches to N-bonded,

finally (high cathodic) denitrilates

CN¯ads

nitrile

[204] (2004) Au-SnAu-N

(of 4CP)Au(CN)4¯

nitrile

Au-C

(of CN¯)

Surface complexes by coadsorption

SFG - Au(hkl)/CN¯+ CP+ - CV

Modification of CN¯ adsorption by CPC

peak shift &c.d. reduction

(111) CN¯

(210) CN¯

(111) CN¯ + CP+

(210) CN¯ + CP+

0.1M NaClO4, 25 mM KCN,2mM CPC

[212] (2004)

Au(hkl)/CN¯+ CP+ - SFG, Au(hkl)

(210) CN¯ (210) CN¯+CP+

(111) CN¯ (111) CN¯+CP+

Ionic couple between CN¯ and CP+, weakening CNads¯

surface

ionic

couple

(111): more compact CN¯ more loosely adsorbed ionic couple with CP+

[168] (2001)

BDMPAC

I111/I220~10 no BDMPAC

I111/I220~3 Au powder XRD

I111/I220~1 with BDMPAC

Multiple twinning pentagonal shape

Preferential ads. stabilising (210) vs (100) star shaped

Competition of coadsorbates

for crystal faces

[186] (2002)

BDMPAC

cathodic

adsorption

of QAS+

QAS also impacts HER opens to reactivity

no BDMPAC with BDMPAC

n(CN¯)

n(Au-H)

2.4) Reactivity

2)(CNAu

e Au

OH2

eH*

???

low-c.d. pathway

high-c.d. pathway

Hat formation

attack by Hat

CNads¯ REACTS AT Au …[273] (2008)

[273] (2008) … AS WELL AS AT Ag, though in a different way …

linear polycyanogencyclic polycyanogen

[408] (2015)

@Ag and even higher cathodic polarisations … compounds with H appear too

H2O D2O

d(NH2)/d(ND2)

n(NH)/n(ND)

ns(CH),nas(CH),ns(CD),nas(CD)

n(OH),n(OD)

d(C=C=H)

… BUT NOT @Cu.[273] (2008)

3) BEYOND CN¯: CN¯-FREE Au ECD BATHS

S-bonded

bidentate

O-bonded

n(S-S)

asymm: O-bonded

asymm: S-bonded sulphite

symm. SO32- stretch

Sulphites [189] (2002) Raman

lo-: cathodic passivation S film

due to sulphite reduction S film can be

oxidised or reduced (to HS¯) electrochemically

(empirical processes rely on additives, but

appropriate choice of allows to avoid this)

Thiourea [207] (2003)

C=SNH2 CN CN+CS

SO42- (supporting ellyte)

dSCNN)

Cathodic:

vertical with NH2 on surface

Au-N

flat

Au-C Au-NAu-S

Thiourea: potential-dependent reorientation

Au+

Thiourea @Au: from anodic adsorption to oxidative desorption

4) Cu-INTERCONNECTS (VIA FILLING)

4.1) Suppressor (PEG)

4.2) Accelerator (SPS)

4.3) Levellers

4.4) The full package

Background:

Additive packege in Cu ECP for semiconductor fabrication

Suppressors: inhibit growth outside features (act on flats)

Accelerators: enhance Cu growth in trenches (act in holes)

Levellers: inhibit overgrowth (act on humps)

Background:

Levellers in Cu ECP for semiconductor fabrication

5 mA cm-2

No additives

“Accelerator”

Full package, incl. levellerTarget finish

After CMP

4.1) Suppressor (PEG)

(I): lo-cd pathway

(II): hi-cd pathway

[245] (2006)SUPPRESSOR: PEG

SERS [217,221,245], ERS [226]

Adsorbs & reacts

crucial role of Cl¯

The suppressor alone does not improve much morphology,

but yields more compact layers

[221,226] (2006)

ERS shows notable incrase in

reflectivity with PEG

no PEG

with PEG

4.2) Accelerator (SPS)

ACCELERATOR: SPS bis-3-sulfopropyl-disulfide Na salt

SERS [233,234] (2006)

Stark tuning

of SPS bands

n(Cu-Cl)

no Cl¯ almost no signal

(apart from narrow cat range)

n(Cu-O)intensity drops with cathodic

polarisation reactivity (next)

with Cl¯: several spectral features

show up in whole ECD range.

n(S-S)

-0.5 mA cm-2

Cathodic reactivity of SPS

SPS: bis-3-

sulfopropyl-disulfide

MPS: mercapto-

propyl-sulfonate

4.3) Levellers

(among other investigated, I selected the following 2 examples)

4.3.1) CTDB

4.3.2) BPPEI

SERS

potential-dependent spectra

Reaction (low cat):

770 N-H wag ,

1425 N=N str ,

1515 R-NH3+ str

Reaction (high cat):

2110 CN¯ads str

“Reorientation”:

710 Ar-oopb ,

980 Ar-rs ,

1172 Ar-ipb ,

1218 ArCN st ,

1600 quad st ,

2233 CN st

CTDB [294] (2010)

SERS – potential-dependent spectra - 2

Reaction (low cat):

1425 N=N str , 1515 R-NH3+ str

Reaction (high cat):

2110 CN¯ads str

low cat

hi cat

SFG: IR Ar range, VIS variable , pH 7

• For 0.05E>-0.5 V: no signal, VIS

• For E-0.5 V: enhanced band

• Band assignment:

Ar-CN str. of 3-cyano-aniline

• Unreacted Q and ACET have

vibrations in this range, but no absorption owing to surface selection rules

•DFT of 3CA: IR and Raman double peak,•3CA bears no chromophore, DR due to VIS absorption by the chemisorption bond

[269] (2008)

SFG: IR CN range, VIS=532 nm, pH 7

• No discernible peaks for E>-0.5 V

• For E-0.5 V: positive band

• No SFG enhancement• VIS,INPUT=532 nm off VIS

absorption peak of unreacted Q

• Reaction products have no chromophores

• Adsorption orbital of 3CA to Cu absorbs at 442 nm.

• Non-DR: phase information can help discriminate between the

adsorption modes allowed by surface

selection rules:

positive band: N facing Cu

• Tentative band assignment:

3-cyano-aniline, adsorbed via CN

SFG: IR CN range, VIS=532 nm, pH 3

• No discernible peaks for E>-0.5 V

• For E-0.5 V: negative band

• No SFG enhancement• Bathochromic shift not enough to

bring VIS absorption in resonance with VIS input

• Band inversion nitrile inversion• Protonation and formation of NH3

+

• Preferred adsorpion through QA moiety

SFG: IR CN range, VIS=532 nm, pH 0.5

• Strong SFG enhancement: over 100

• DR-SFG• bathochromic shift brings VIS

absorption in resonance with VIS input

• Positive band: owing to DR, phase information is no longer diagnosticdiagnostic of -CN orientation

• For E-0.5 V change in the peak position and intensity increase

• Peaks correspond to unreacted Q• E>-0.5 V: straightforward

• E-0.5 V: no VIS absorption of reaction products expected

• Peak shifts due to change of chemical environment for adsorbed unreacted Q

• Intensity increase due to change in electronic structure of Cu-absorbate interface

[262] (2007)BPPEI

On the basis of experience with BDMPA+

We developed a polymeric leveller: benzyl-Phenyl modified Polyethyleneimine: BPPEI

(MW ca. 50,000)

JGB

BPPEI

[263] (2009)

In situ SERS during Cu electrodeposition

in the presence of BPPEIPrincipal bands:

991: ring breathing1338: Ph-N stretch. for QAS1381: Ph-N stretch. For DMA1481: rs-ipd combinat. band1590: ring stretch. for DMA1629: ring stretch. (for QAS)

Stark tuning

QAS DMA

In QAS: benzyl flat, phenyl vertical

DMA/QAS

In situ SERS in the presence of BPPEI

dynamic spectroscopy

-500mV -850mV

DMA/QAS

QAS DMA

In situ ERS at Cu electrodes

in the presence of 4CP, JGB and BPPEI

Interband transition shifts

Adsorbatestates

4.4) The full package

[263] (2009)

Lo-cd: suppressor (PEG) dominates

Intermediate-cd: accelerator (SPS) dominates

Hi.cd: leveller (BPPEI) dominates

Suppressors: always adsorbed

Accelerators: selective adsorption in cathodic regions (SPSMPSMPSads),

easy mass transporteffective in holes

(higher-q at the mouth than at the bottom)

Levellers: selective adsorption in reacting regions (QASDMA: higher density of adsorbable species),

sluggish mass transport (polymer)effective on humps

5) ECD FROM RTIL

ELECTRODEPOSITION FROM RTIL

1) [BMP][TFSA]: well established for electrodeposition processes

hydrophobic, good stability (to T and hydrolysis), wide elchemical window.

2) [EMIm][TFSA]: lower viscosity, higher conductivity.

~PZC

a few ionic layers

n.b.: in aqueous solutions: ~20 mF cm2

[318] 2010DL structure at Au in the presence of CN¯

SFG DFG

SFG DFGStark tuning: ~3 cm-1 V-1

aqueous: ~20 cm-1 V-1

CH3, CH2 wagging

oop+ip ns(S=O)

in SO2

of [TFSA]

n(C-F) of CF3

Both ions adsorbed over extended

potential range:

Mulliken charge distribution and

bond delocalization – in conjunction

with molecular reorientations –

accomodate changes in applied

electric field without expelling either

species from interface.

~8Å

Stark

~30Å

Field screening for CN¯ (see our data with SAM)

ECD SFG [344] 2011

n.b. KCN ~3 cm-1 V-1

non-reacting adsorbate

reacting adsorbate

ring

butyl

Au ECD anodic: equatorial

high q(CN¯ads) vertical

with Au(CN)2¯:

no TFSA¯ at interface

Changes in orientation

& conformation of BMP+

cathodic: axial

electrostatically

favoured adsorption through N atom

ring // plane low q(CN¯ads)

+ tail

@0 V

VIS resonance with adsorption bond

2D-SFG

6) MONITORING ECD OF METAL/OXIDE COMPOSITES

MONITORING NON-METALLIC COMPONENTS IN COMPOSITE ECD

Au-Y2O3 [350] Raman (2012)

ECD of Ni:

(i) nucleation

(ii) 3D growth + roughening

ECD Ni/CeOx:

(i) Ni nucleation,

(ii) formation of cerium oxide,

(iii) secondary nucleation,

(iv) 3D growth and roughening.

Ni-ceria [376] ERS-Raman (2012)

7) ACTIVITY OF ELECTRODEPOSITED ELECTROCATALYSTS

FOLLOWING PERFORMANCE OF ELECTRODEPOSITED ELECTROCAYALYSTS

Pt-NP/WC for EtOH oxidation: FTIR, SFG, SPEM [377] (2013)

FTIR SFG

Follow changes in electrooxidation mechanism with electrocatalyst ageing:

adsorption of reagent (EtOH), reaction product (acetate) and …

… catalyst poison (CO)

Attending changes in chemical state of Pt and WC support.