shreya mukherjee, hao zhang, gang wuengineering.buffalo.edu/content/dam/engineering/chemical... ·...

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