SYNTHESIS of NEW NON-PGM CATALYSTS FOR POLYMER ELECTROLYTE MEMBRANE (PEM) FUEL CELL Shiqiang Zhuang
[email protected] PI: Eon Soo Lee, Ph.D. ADVANCED ENERGY SYSTEMS & MICRODEVICES LABORATORY
Mechanical and Industrial Engineering 6/28/2015
Content 1. INTRODUCTION
2. SYNTHESIS OF NITROGEN DOPED- GRAPHENE CATALYST BY BALL MILLING 3. CHARACTERISTICS ANALYSIS 4. FUTURE PLAN
1. Introduction PEM Catalysts: Platinum (Pt) => non-platinum group metal material (non-PGM) Power
e
Anode gas supply channels
Catalyst layer
GDL
Cathode GDL
PEM
H
N-G catalyst
e
H2O
O2
H2
MEA
Nitrogen doped graphene (N-G) catalysts Advantages: 1) The cost of materials is much less than precious metal-based catalyst; 2) High oxygen reduction reaction (ORR) activity.
2. SYNTHESIS OF NITROGEN DOPED- GRAPHENE CATALYST BY WET BALL MILLING 1. Conventional chemical synthesis methodologies of Nitrogen doped-Graphene catalyst (N-G) • Chemical vapor deposition (CVD) • Heat treating • Gas annealing • Plasma treatment 2. Mechanochemical synthesis approach for N-G catalyst — High Energy Ball Milling. Advantages: 1) The machine can be used for dry or wet material; 2) simple operating conditions, and grinding in a closed machine, with no dust flying; 3) immediate stop or start; 4) the mill can be filled with inert gas instead of air; 5) low temperature synthesis.
Ball milling principle
TABLE 1. SYNTHESIS METHODS AND NITROGEN CONTENT OF RELATED NITROGEN DOPED-GRAPHENE CATALYST
Our research
Synthesis method
precursors
N content, %
application
Wet Ball milling
GO, melamine
10.40%
ORR
Dry Ball milling
Graphite, nitrogen (N2)
3~10%
ORR [6-10]
1.6~16
ORR [1]
7.1~10.1
ORR [2,3]
3~5
ORR [4]
8.5
ORR [5]
Conventional mechanochemical approach Chemical vapor deposition (CVD)
Conventional chemical approaches
Heat treating
Gas annealing
Plasma treatment
Cu foil as catalyst, NH3/He GO, melamine or
cyanamide GO, NH3 GO after thermal expansion, N2 plasma
Our Research — Synthesize N-G catalyst by wet ball milling Dry
Wet
a
Water Ball mill
Ball mill c
c
Figure 1. (a) Conventional dry ball milling approach to synthesize N-G catalyst, b,c) SEM images of pristine graphite (b) and N-G catalyst (c) [10].
MOF
b b
Figure 2. a) A schematic representation of our current wet ball milling approach to synthesize N-G/MOF catalyst, b,c) SEM images of our NG/MOF catalyst (b) and high porosity structure of our catalyst (c).
Application of MOF in our N-G catalyst synthesis Advantages of using MOFs as carriers for catalysts: a) MOF: good electrical conductivity, can enhance the electron transfer rate; Figure 3. (a,b) Zeolitic imidazolate framework (ZIF, one type of MOF), (c) micrograph of the physical structures of MOF supported material. [11].
b) MOF: make new catalysts have high porosity and big surface area; c) MOF: high chemical stability and high thermal stability (up to 550℃), can enhance the stability of catalytic particles.
Figure 4. Structure of N-G/MOF catalyst.
Deposition of catalyst on carrier particles Conventional deposition approach
Our deposition approach
Methodology: Wet Impregnation
Methodology: Wet ball milling
Precipitation in the pores of a solid carrier support Procedure: 1. Addition of catalyst in water; 2. Stirring; 3. Addition of MOF; 4. Stirring drying heat treating.
Procedure: 1. Addition of catalyst in water; 2. Addition of MOF; 3. Ball milling and drying.
Water
Ball mill
Figure 5. Schematic diagram of wet impregnation method.
Figure 6. Schematic diagram of new deposition approach.
3. CHARACTERISTICS ANALYSIS TABLE 2. CHARACTERIZATION METHODS Catalyst Property
Characterization Test
Internal surface area
N2 adsorption (BET)
XRD Particle size
RDE
XRD
Bragg’s Law: nλ=2dsinθ
SEM
Zetasizer, XRD
(From: http://www.basj.com/1657.html)
TEM
X-ray photoelectron Elemental composition
spectroscopy (XPS) (www.wikipedia.org)
Scanning/Transmission Surface Structure
Electron Microscopy (SEM/TEM)
Electrochemical activity
Rotating disk electrode (RDE)
XPS
Zetasizer results
Ball mill parameters: 1) Rotating speed: 500 RPM, 2) Size of grinding balls: 0.85 mm, 3) Time length: 16 hr.
Ball mill parameters: 1) Rotating speed: 300 RPM, 2) Size of grinding balls: 1.7 mm, 3) Time length: 5 hr.
SEM
Catalyst deposition by wet ball c milling
b N-G a
a
N-G/MOF
c b
c MOF
b
Figure 7. SEM images of (a) surface structure of N-G catalyst without MOF, (b) structure of MOF without N-G catalyst, and (c) structure of new particles—N-G deposited on MOF by wet ball milling.
a Element survey
b Carbon
XPS results Figure 7. (a) XPS survey spectra of our N-G catalyst (GO:Melamine=1:10), (b) C 1s, (c) N 1s, (d) O 1s.
Table 3. Elemental composition of N-G catalyst
c Nitrogen
d Oxygen
Element
Weight%
Atomic%
C
64.32
69.40
N
11.80
10.40
O
23.88
20.20
Totals
100.00
100.00
Influencing Factors Analysis — N content measured by XPS Table 4. Mass Ratio of Reactants
Table 5. Rotation Speed
(rotation speed 500RPM, 0.85 mm balls, 16 hr )
(reactants mass ratio 1:6, 0.85 mm balls, 16 hr)
Mass ratio (GO:Melamine)
Nitrogen Content %
Rotation Speed (RPM)
Nitrogen Content %
1:2.5
3.71
350
6.34
1:6
8.69
500
8.69
1:10
10.40
650
8.91
RRDE Result
n=3.97
n=3.41
n=3.35 n=3.23
N%=3.71
N%=8.69
N%=10.40
4. FUTURE PLAN 1. Further optimization of synthesizing N-G catalyst by ball milling approach.
2. Influencing factors — the effects on properties of final products. 3. Performance test — real PEM fuel cell with our NG/ZIF catalyst. 4. Next stage — Synthesis of multiple elements dopedGraphene catalyst by ball milling approach.
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