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Metal‐free and Nonprecious Metal Materials for Energy‐relevant Electrocatalytic Processes 

Shizhang Qiao （乔世璋）s.qiao@adelaide.edu.au

18‐19 January 2016,  Perth

The University of Adelaide, Australia

1. ORR Catalysis

OUTLINES

4. Summary

2. OER Catalysis

3. HER Catalysis

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1. ORR and Catalysts

Pathway Acidic medium Alkaline medium

4e– O2+4H++4e–2H2O O2+2H2O+4e–4OH–

2e– O2+2H++2e–H2O2 O2+ H2O+2e–HO2–+OH–

H2O2+2H++2e–2H2O H2O+ HO2–+2e–3OH–

Cathodic oxygen reduction reaction (ORR) pathway (2e vs. 4e)

The main trend in ORR electrode development is replacing precious Pt with higher-performance, lower-cost, and longer-life catalysts!

Pt/C electrode:

an efficient cathodic oxygen reduction reaction (ORR) catalyst

Low durability (CO poison and Carbon degradation)

High Cost, limited supply

Carbon-based Metal-free ORR Catalysts: Unique electronic properties

Zheng, Qiao* et al, Small, 2012, 8, 3550-3566. (202 citations)

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Carbon-based -Metal-free Catalysts: g-C3N4

Zheng, Qiao*, et al, Energy Environ. Sci., 2012, 5, 6717-6732. (327 citations)

• Highest nitrogen content (61%)

• Highly regular structure

• Low cost, facile synthesis

• Potential ORR catalyst, substitute of Pt

• Non-conductive nature

• Blocking electron transfers

Graphene‐based metal‐ free ORR electrocatalysts

Engineering graphene for an enhanced catalytic activity - heteroatoms doping

Graphene:

semimetal, little catalytic activity

Single-doped graphene with heteroatoms:

Tailoring the electron-donor property of graphene toenhance its reactivity

Dual-or Tri-doped graphene:

A synergistic coupling effect to result in a uniqueelectronic structure and further enhanced activity

Our strategy (synergistic effects):

B,N-grapheneS,N-graphene

J. Liang, S. Qiao*, et al, Angew. Chem. Int. Ed., 2012, 51, 11496. (439 citations)Y. Zheng, S. Qiao*, et al, Angew. Chem. Int. Ed., 2013, 52, 3110. (258 citations)

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A novel two-step doping process from GO: first N in low temperature then B in high temperature

A high purity of B,N co-doped graphene without hybrid h-BN formation

1.1 B,N-co-doped graphene: synthesis and chemical composition

Potential synergistic effect: Enhanced ORR electrocatalytic activity. A platform for theoretical calculation: Chemical interaction between B and N.

Y. Zheng, Y. Jiao, L. Ge, M. Jaroniec, S.Z. Qiao*, Angew Chem. Int Ed. 2013, 52, 3110-3116. (258 citations)

1.1 B,N-co-doped graphene: electrocatalytic ORR performances

Significantly enhanced ORR performance than single-doped graphene (N-graphene, B-graphene) and one-step synthesized h-BN/graphene hybrid :

Closer on-set potential to Pt/C

Higher ORR current density

Better electrocatalyticefficiency than single-doped graphene and h-BN graphene

Higher stability than Pt/C

Synergistic effects 1+1>2

Y. Zheng, Y. Jiao, L. Ge, M. Jaroniec, S.Z. Qiao*, Angew Chem. Int Ed. 2013, 52, 3110-3116. (258 citations)

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300 600 900 1200 1500

S

C

N

O 4.6 %C 88.88 %S 2.02 %N 4.5 %

I

Binding Energy

O

168 166 164 162

Binding Energy / eV

C-S-C 2p3/2

C-S-C 2p1/2

A simple one-pot doping using all solid and commercial precursors

S and N are simultaneously doped into different sites of graphene.

Precursors undergo total thermal decomposition, no residual or side products formed.

No by-product formation

1.2 Mesoporous S,N-Graphene Electrocatalyst

J. Liang, S. Qiao*, et al. Angew. Chem. Int. Ed. 2012, 51, 11496-11500. (438 citations)

-0.9 -0.6 -0.3 0.0 0.3

-4

-2

0

2

N2

O2

J /

mA

cm

-2

E vs. Ag/AgCl / V

0.2 0.0 -0.2 -0.4 -0.6 -0.8

12

8

4

0

0 rpm

2000 rpm

J /

mA

cm

-2

E vs. Ag/AgCl / V

0.02 0.03 0.04 0.05

0.1

0.2

0.3

0.4

J -1

/ mA

-1 c

m2

-1/2 / rpm-1/2

G

N-G

S-G

N-S-G

Pt/C

0

5

10

15

20

25

30

35

n=3.0n=3.0

n=3.3

n=3.6

GN-GS-G

J k / m

A c

m-2

Pt/C N-S-G

n=4

0.2 0.0 -0.2 -0.4 -0.6 -0.812

8

4

0

J -1

/ m

A c

m-2

E vs. Ag/AgCl / V

Pt N-S-G S-G N-G G

1.2 S,N-graphene: ORR activity

ORR performance: Much better than

S-graphene

N-graphene

Synergistic effect The interaction of S and N dopants enhance both charge and spin density of active C atom

J. Liang, S. Qiao*, et al. Angew. Chem. Int. Ed.. 2012, 51, 11496-11500. (439 citations)

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EISA

PS/Resol/F127

ThermalPolymerize

PS/PF

OMM‐PF

AcetoneCyclohexane

Melamineg‐C3N4

Resol+F127 in EtOH

PS Monolith

N‐G

N‐OMMC

N‐G

N‐G

N‐G

150 nm 50 nm

5 nm50 nm

N‐Grapheneon Carbon N‐Graphene

3D‐Macropore 2D‐Mesopore

Dual template to form ordered macroporesand mesopores

In‐situ growth of N‐doped graphene J. Liang, S. Qiao*, et al. Advanced Materials 2013, 25, 6226-6231.

1.3

1.3 N‐graphene/hierarchical porous carbon hybrid for ORR

10 20 30 400.0

0.5

1.0

dV

/d(l

og

D)

Pore Size / nm

0.0 0.5 1.0

800

Qu

anti

ty

Ad

sorb

ed

P/P0200

-0.9 -0.6 -0.3 0.0 0.3-4

-2

0

2

Jp=1.81 mA cm-2

E vs. Ag/AgCl / V

N2

O2

J / m

A c

m-2

0.0 -0.4 -0.8-8

-4

0

E vs. Ag/AgCl / V

J / m

A c

m-2

MIX Pt/C N-OMMC-G N-OMMC N-G

-5 -4 -3 -2-0.5

-0.4

-0.3

-0.2

-0.1

log |(iL

·i)/(iL-i)|

E v

s. A

g/A

gC

l / V

N-OMMC-G N-OMMC N-G MIX

0

70

140

210

280

350

MIX N-GN-OMMC

Taf

el S

lop

e / m

V d

ec-1 Low Potential

High Potential

N-OMMC-G

Few‐layered graphene sheets

Large surface area & excellent accessibility

Synergistically enhanced ORR performance

Advanced Materials

J. Liang, S. Qiao*, et al. Advanced Materials 2013, 25, 6226-6231 (insider Front Cover, 79 citations).

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Y. Jiao, Y. Zheng, M. Jaroniec, S. Qiao*, J. Am. Chem. Soc. 2014, 136, 4394-4403. (100 citations)

1.4 Origin of ORR activity of doped graphene electrocatalysts

B, N, O, P, S doped graphenes

Molecular orbital concept

196 192 188

Inte

nsity

(a.

u.)

B1s

B2O

3B-2C(-O)

BC3

b

Binding Energy (eV)

404 400 396

Inte

nsity

(a.

u.)

Graphitic N

Pyrrolic N

N1s

Pyridinic Nc

Binding Energy (eV)

168 166 164 162 160

Inte

nsity

(a.

u.)

p1/2

S2p

C-S-C

p3/2

f

Binding Energy (eV)

140 135 130 125

Inte

nsity

(a.

u.)

P2p

P-3C(-O) Ph3P

e

Binding Energy (eV)

296 292 288 284 280

C1ssp2C-C

-

a

Binding Energy (eV)

Inte

nsi

ty (

a.u

.)

536 532 528

Inte

nsi

ty (

a.u

.) O-C=O

O1s

O=C C-OHC-O

epoxy/

pyran

d

Binding Energy (eV)

Graphite, B, N, O, P, S doped graphenes. Five heteroatoms induce 13 differentdoping configurations in graphene clusters with very different electronicproperties, yielding 32 possible ORR active sites.

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0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-13

10-11

10-9

10-7

10-5

GOOH*

(eV)

P-G G

S-G

O-G

N-G

log(

j 0) (A

/cm

2 )

B-G

X-GPt

Exchange current density

-0.4

-0.2

0.0

0.2

experimental value

O-G GS-GP-GN-G

Ons

et P

ote

ntia

l vs.

NH

E (

V)

B-G

predictive value

On‐set potential

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

Reaction coordinates

Fre

e en

erg

y (e

V)

OOH-

OOH*

UNHE

= -0.08 V

O2

gN-G

X-G

0.16 eV

Pathway selectivity

0.2 0.4 0.6 0.8 1.00

-1

-2

-3

-4

-5

-6 @ -0.1 V (-2.68 mA/cm2)

@ -0.2 V (-5.23 mA/cm2)

@ -0.3 V (-6.01 mA/cm2)

X-G

J k@vs

NH

E (

mA

/cm

2 )

GOH*

(eV)

N B P O S G

Kinetic current density

Y. Jiao, Y. Zheng, M. Jaroniec, S. Qiao*, J. Am. Chem. Soc. 2014, 136, 4396-4403. (100 citations)

(1) Advanced Functional Materials 2014, 24, 2072; (2) Chemical Communication 2013, 49, 7705.

1.5 Non-noble metal @ N-carbon catalysts: ORR activity

(3) Chemical Communications 2015, 51, 7516;(4) Chemistry of Materials 2014, 26, 5868; (5) Journal of Materials Chemistry A 2013, 1, 3179.

spheres

square/cubic

ellipse

Fe‐N synergistic effect enhanced the ORR performance and change the mechanism;

XPS and Raman spectrum proved the existence of Ag‐N interaction;

The ORR performance is close to Pt;

The ORR performance is correlated to shape of Mn3O4 nanocrystals .(1) Mn‐N‐graphene 

(2) Fe‐N doped graphitic carbon (3) Ag@N‐rGO(4) CuO@N‐rGO

Mn-N Fe-N Ag-N Cu-N

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OER in alkaline media

4OH- → 2H2O + O2 + 4e- (in alkaline solutions)

2H2O → 4H+ + O2 + 4e- (in acidic or neutral solutions)

High overpotential

Low activity

Inferior kinetics

Challenges in OER process

2. OER and Catalysts

2.1 N, O-dual doped carbon-based electrode (substrate-free)

O2

Chen S., Qiao S.Z.* et al. Adv. Mater, 2014, 26, 2925-2930. (49 citations)

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O2

2.1 N, O-dual-doped carbon-based

Chen S., Qiao S.Z.* et al. Adv. Mater, 2014, 26, 2925-2930. (49 citations)

Onset potential

Current density

Tafel slope

Catalytic kinetics

Durability

Stability

2.2 Hydrated oxygen evolution electrocatalyst

Hydrated electrocatalyst

Dehydrated electrocatalyst

Chen S., Duan J., Jaroniec M., Qiao S.Z.*, Angew. Chem. Int. Ed., 2013, 52, 13567-13570. (72 citations)

Ni Co double hydroxides

Hybrid hydrogel

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2.2 Hydrated oxygen evolution electrocatalyst

O2

Chen S., Duan J., Jaroniec M., Qiao S.Z.*, Angew. Chem. Int. Ed., 2013, 52, 13567-13570. (72 citations)

EIS: internal resistance,favorable transport

12 h chronoamperometric test

1200 1000 800 600 400 200 0

C=C

C-OH

sp2 C in g-C3N

4

-COOH

positive CN cycle

N(-C)3

C=N-CC 1sN 1s

C

N

Inte

nsity

(a.

u.)

Binding energy (eV)

O

405 402 399 396 393

interactwith CNT

292 288 284 280

2.3 3D g-C3N4 nanosheet-CNT composite oxygen evolution catalysts

Ma, T. Y., Qiao, S.Z.*, et al. Angew. Chem. Int. Ed., 2014, 53, 7281-7285. (80 citations)

exfoliation

Strong interation between CNT and N in g-C3N4

Hight N content of 23.7 wt%

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0.0 0.5 1.0 1.5

0.3

0.4

0.5

IrO2-CNT

90 mV decade-1

bulk g-C3N

4-CNT

105 mV decade-1

Ove

rpot

entia

l vs.

RH

E (

V)

Log[J (mA cm-2)]

g-C3N

4 NS-CNT

83 mV decade-1

(b)

1.0 1.2 1.4 1.6 1.8

0

20

40

g-C3N

4 NS-CNT

IrO2-CNT

bulk g-C3N

4-CNT

CNT g-C

3N

4 NS

J (m

A c

m-2)

(GS

A)

E vs. RHE (V)

(a)

1.0 1.2 1.4 1.6 1.80

1

2

3

4

5O

2-saturated

I ring a

t Erin

g =

1.5

0 V

(A

)

E vs. RHE (V)

4OH- O2+ 2H

2O + 4e-

(a)

0 10 20 30 40-50

-40

-30

-20

-10

0

Idisk

= 200 A

I ring a

t E

ring

= 0

.40

V (

A)

Time (s)

Idisk

= 0

N2-saturated

0 10 20 30 40 50

GCPtPt

Ering

Catalyst

OER

PtPt

ORR

OH- O2 OH-OH- O2 OH-

(b) (d) (e)

1.0 1.2 1.4 1.6 1.8

0

5

10

15

g-C3N

4 NS-CNT

bulk g-C3N

4-CNT

50 mV s-1

J (m

A c

m-2)

(GS

A)

E vs. RHE (V)

5 mV s-1

50 mV s-1

5 mV s-1

0 10 20 30 40 500

5

10

15

20

(J-J0 )/J

0 (%)

Scan rate (mV s-1)

(c) (f)

0 2 4 6 8 100

25

50

75

100

J/J 0 (

%)

Time (h)

86.7%

0 200 400 600 8001.52

1.54

1.56

1.58

g-C3N

4 NS-CNT

IrO2-CNT

g-C3N

4 NS-CNT

E vs. R

HE

(V)

Time (s)

(c)

2.3 3D g-C3N4 nanosheet-CNT composite oxygen evolution catalysts

Catalytic activity Reaction kinetics Long-term stability

Reaction pathway

Low ring currentno hydrogen peroxide four-

electron water oxidation

Reaction mechanism Mass transportation

Ma, T. Y., Qiao, S.Z.*, et al. Angew. Chem. Int. Ed., 2014, 53, 7281-7285. (80 citations)

2.4 Metal-Organic Framework-Derived Co3O4-Carbon Porous Nanowire Arrays for Reversible OER/ORR

Ma, T. Y., Qiao, S.Z., et al. J. Am. Chem. Soc. 2014, 136, 13925-13931. (73 citations)

Hydrocarbon layer

Cobalt‐oxygen layer

AmorphousCarbon 251 m2 g‐1

pore size: 5 nm

C: 52.1 %

Enhanced electron

conductivity

The highest for nanowire arrays

C: 52.1 %

Enhanced electron

conductivity

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Well alignednanowire array

Ma, T. Y., Qiao, S.Z., et al. J. Am. Chem. Soc. 2014, 136, 13925-13931. (73 citations)

Slit‐like mesopores

Homogeneously distributed Co and C

(311) planeof Co3O4

Closely interacted C and Co3O4

High OER activity

o High conductivity by in situ carbon introduction

o Large active surface area

o Favourable reaction kinetics in the nanowire array structure

o Strong binding between nanowirearrays and Cu substrate

Nanowire arrays on Cu foil

Ma, T. Y., Qiao, S.Z., et al. J. Am. Chem. Soc. 2014, 136, 13925-13931. (73 citations)

Faradaiceffciency: 99.3% 

Favorable kineticsHigh OER activity 4‐e‐ pathway 

High OER activity

Favourable kinetics

High efficient reaction pathway

High Faradaic efficiency

Long term durability 

Strong cyclic stability

Strong methanol tolerance

Bi‐function for both ORR and OER. 

Excellent reversibility: ∆E = 0.74 V 

Methanol addition

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• First record of electrocatalytic hydrogen evolution reaction (HER) by a non‐metallic material.

• Comparable electrocatalytic activity with state‐of‐the‐art metallic catalysts.

• A combined theoretical and experimental study.

Aberration‐corrected HRTEM and HR‐EELS mapping

The hybrid (g‐C3N4@N‐graphene) is a ultrathin nanosheet with some g‐C3N4

nanodomain (islands) on the surface.

3. HER and Catalysts 3.1 metal free g-C3N4@graphene

Y. Zheng, S. Qiao*, et al. Nature Commun. 2014, 5: 3783 (123 citations)

Experiments: Synchrotron-based near edge X-ray adsorption fine structure

Calculation: Density functional theory

Combine experiments and calculation: There is a strong chemical interaction between g-C3N4 and N-graphene, which promote the rapid electron transfer between two layers

Y. Zheng, S. Qiao*, et al. Nature Commun. 2014, 5: 3783. (123 citations)

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High HER activity with low overpotential

DFT calculation: Free energy diagram and volcano plot

Combine experiments and calculation: Newly developed C3N4@NG non-metallic hybrid shows highly efficient hydrogen reduction and the activity is comparable with traditional metallic materials

Y. Zheng, S. Qiao*, et al. Nature Commun. 2014, 5: 3783 (123 citations)

Tafel slope Robust stability in both acidic and alkaline solutions

• Open up a new avenue for graphene materials’ electrochemical applications.

• Pave the way of heteroatoms doped graphene for electrocatalytic HER applications.

• A combined theoretical and experimental study.

Theoretical prediction: Density functional theory

N and P heteroatoms could co‐activate the C in graphene to induce a synergistically enhanced reactivity toward HER

Y. Zheng, S. Qiao*, et al. ACS Nano. 2014, 8, 5290-5296.(70 citations)

3.2. HER – P,N doped graphene catalysts

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0

1x10-7

2x10-7

3x10-7

i0 in 0.5 M H

2SO

4

i0*100 in 0.1 M KOH

e

P-G N-G N,P-G-1

i 0 (

A/c

m2 )

0.0 0.4 0.8 1.2 1.6 2.010-12

10-10

10-8

10-6

G P-G N-G N,P-G-1

I 0 (

A/c

m2)

|GH*

| (eV)

0.5 M H2SO

4

0.1 M KOH

f

-0.6 -0.5 -0.4 -0.3 -0.2 -0.1-10

-8

-6

-4

-2

0

Graphite P-graphene N-graphene N,P-graphene-1

Cur

rent

Den

sity

(m

A/c

m2)

Potential vs. RHE (V)

a

0.5 M H2SO

4

-2.5 -2.0 -1.50.35

0.40

0.45

0.50

0.55

0.60b

N,P-graphene-1(91 mV/decade)

N-graphene(116 mV/decade)

P-graphene(133 mV/decade)

Log I (A/cm2)

HE

R O

verp

oten

tial (

V)

Graphite(206 mV/decade)

Highly active HERSynergistic effect

Applicable in both acid and base solutions

A good consistence of theoretical prediction and experimental verification

Better than single‐doped graphene

Y. Zheng, S. Qiao*, et al. ACS Nano. 2014, 8, 5290-5296.(70 citations)

3.2. HER – P,N doped graphenecatalysts

5. Summary

1. Mesoporous and macroporous g-C3N4/C composite metal-free catalysts have high ORR activity, excellent stability and very high reaction efficiency.

2. Dual non-metal elements doped graphenes have a synergistic coupling effect which leads to enhanced ORR catalytic activity.

3. Metal-free electrocatalysts are also developed for Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER).

Review & Feature Articles

Chem Soc Rev, 2015, 44, 2060-2086. (34 citations)

Angew Chem, 2015, 54, 52-65. (46 citations)

Energy & Environmental Science, 2012, 5, 6717-6731. (327 citations)

Small, 2012, 8, 3550-3566. (202 citations)

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Acknowledgement

$$$ Australian Research Council

$$$ The University of Queensland

$$$ The University of Adelaide

$$$ Industrial partners

Thank you for your attention!