shreya mukherjee, hao zhang, gang wuengineering.buffalo.edu/content/dam/engineering/chemical... ·...
TRANSCRIPT
Electrochemical Synthesis of Ammonia from Nitrogen and Water at Ambient Conditions
Shreya Mukherjee, Hao Zhang, Gang Wu
Vision
Long term Objective : Back up of Haber
Bosch Process : synthesize ammonia with
minimum energy and without using H2
Major Limitation : Extremely slow
kinetics of the process
Possible Solution : Develop catalyst
that can reduce nitrogen at ambient
conditions
Background :
Approach
Acknowledgement
.
http://www.dtu.dk/nyheder/2017/01/elektrokatalyse-kan-sikre-groen-omstilling?id=fa31e2ea-9427-418e-9437-318dfb497816
Area : Development of Electro Catalysts
for synthesizing NH3 at ambient conditions
Focus : Non-Precious Metal Free Catalyst
Development
Catalyst Synthesis :
Optimization : Tuning pyrolysis condition to
tune N content
Current Status &
Future plan
Active Site Prediction:
• FE of 10 % have been achieved without
using any precious metal
• Ammonia production rate is comparable
and even higher than some precious
metal catalyst
• Single atom like Ni, Ru on such carbon
framework can be synthesized to further
increase the activity
Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260
Financial supports from the startup fund of
University at Buffalo along with U.S.
Department of Energy, Advanced Research
Projects Agency-Energy (ARPA-e) program
are greatly acknowledged.
Our Goal
Synthesize
ammonia without
using H2 at
ambient
conditions
Initial Motivation:
Metal nitrides based on DFT
Main challenge:
Catalyst decomposition
Further Modification
FeN4 supported on stable N doped carbon derived
from ZIF8
Main Challenge: Evolution of hydrogen
Innovation:
Development of N doped porous carbon with minimum metal content as catalyst
0
1
2
3
4
0.5 M NaOH
0 Fe
Fe-free
20% Fe
1% Fe
Fe-free
0.1 M NaOH
20% Fe
Pro
du
cti
on
Ra
te (m
ol c
m-2h
-1)
0.1 M KOH
1% Fe
Fe-free
0.5 M KOH
500 550 600 650 700 750 800
0.05
0.10
0.15
C-ZIF-1100-1h
Ar, 0.1M NaOH
N2, 0.1M NaOH
N2, 0.1M KOH
Ab
so
rban
ce (a
.u)
Wavelength (nm)
Ar, 0.1M KOH
Mukherjee et al. Nano Energy 48 (2018) 217–226
Investigated Fe-N4 Sites For NRR
Activity
Activity increased as Fe doping was
reduced
Highly disordered
carbon derived
from
ZIF-8 via pyrolysis
under inert
atmosphere
Importance of pyridinic nitrogen vacancy and role of graphitic nitrogen is investigated using DFT studies
Potential (V vs. RHE)
Activation energy required in Haber Bosch process with triply promoted catalyst is 103 kJ/mol
20 40 600
2
4
6
8
Pro
du
cti
on
Rate
(m
ol cm
-2h
-1)
Temperature (oC)
0.1 M KOH
0.1 M HCl
Time (secs)
Ar > N2
N2 > Ar
Ar > N2