Post on 29-Oct-2019
25/01/2016
1
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
25/01/2016
2
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)
25/01/2016
3
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)
25/01/2016
4
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)
25/01/2016
5
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)
25/01/2016
6
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).
25/01/2016
7
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.
25/01/2016
8
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
25/01/2016
9
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)
25/01/2016
10
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
25/01/2016
11
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%
25/01/2016
12
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
25/01/2016
13
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
25/01/2016
14
• 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)
25/01/2016
15
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
25/01/2016
16
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)
25/01/2016
17
Acknowledgement
$$$ Australian Research Council
$$$ The University of Queensland
$$$ The University of Adelaide
$$$ Industrial partners
Thank you for your attention!