New Insights into Electrocatalysis of Nitrogen Reduction to Ammonia

Alex Schechter

Department of Chemical Sciences Ariel University, Israel (salex@ariel.ac.il)

Experimental Setup

Collected Ammonia in the Acid Trap and the Electrolyte

The electrochemical cell

Quantification of Ammonia using Indophenol and Nessler’s method

Indophenol method Nessler’s method

Ammonia Sodiumhypochlorite

Salicylicacid

Indophenolmethod

Voltammetry of N2 Reduction on PGM catalysts in alkaline pH

VulcanXC-72

Ru/C

Pt/C

RuPt/C

PGM-PlatinumgroupmetalRT,ambientpressure,1MKOH

Applied Potential

)E / V vs. RHE(

Rate of ammonia

)mol s-1cm-2(

Efficiency of ammonia produced

(%)

0.123 3.0×10-10 13.20.023 6.12×10-10 4-0.077 6.37×10-10 1.15-0.177 5.95×10-10 0.75-0.277 5.45×10-10 0.35

The Effect of Applied Potential and Temperature

Electrochemical ammonia synthesis at RuPt/C at 50 °C

NRR Catalysts Comparison Catalyst Rate of of NH3

(gNH3 s-1cm-2)Rate of of

NH3

)mol s-1cm-2(

Applied Potential (RHE)

Faradaic Efficiency (%)

Reference

Pt-electrode 1.9× 10−8 1.1× 10−9 1.6 V (Fuel cell configuration)

0.1 Sci. Rep. 3 (2013) 1145

Ru-electrode 3.57 × 10−10 2.1 × 10−11 -1.02 V (Vs. Ag/AgCl)

0.9 Chem. Commun. (2000) 1673–1674.

Fe2O3-CNT 6.11×10-10 3.57× 10−11 -2.0 (Vs. Ag/AgCl) 4.5 Angew.Chem. Int.Ed. 2017, 56,2699 –2703

Au nanorods 4.57×10-10 2.6 × 10−11 -0.2 V 4 Adv. Mater. 29 (2016) 1700001

Au nanoparticles on CeOx-RGO support

2.3×10-9 1.3 × 10−10 -0.2 V

10.1 Adv. Mater. 29 (2017) 1700001

Au subnano- clusters on TiO2

5.9×10-9 3.4 × 10−10 -0.2 V

8.1 Angew. Chemie - Int. Ed. 40 (2001) 1061–1063.

RuPt/C 7.25×10-9 4.2× 10−10 -0.077 V

3.0 Present work

RuPt/C 1.08×10−8 (50° C) 6.3×10-10 -0.077 V 3.8 Present work

Mechanism of Electrochemical Nitrogen Reduction Reaction Nitrogen reduction reaction via a) dissociative and b) associative mechanism.

On-Line Mass Spectrometry Analysis During N2 Electrolysis

After CO adsorption; there was no ammonia formation

Ammonia Formation under CO Adsorption on RuPt/C

N2 Electrolysis -0.1 V

Cycle1

CyclicVoltammetry

Cycle2

LinearSweepVoltammetry

Ammonia Formation under CO Adsorption on Pt/C and Ru/C LS-Voltammogram Ru/C N2 Electrolysis Ru/C at -0.1 V

LS-Voltammogram Pt/C N2 Electrolysis Pt/C at -0.1 V

Proposed Cooperative Reaction Mechanism

Acknowledgments

Sponsors

•  Ministry of commerce (KAMIN prog.)

•  ISF- P.M. Ministry via INREP program

•  Ministry of Energy and Water

•  Ministry of Defense

•  Ministry of Environmental Protection

GroupMembersPostdocs•  Dr.HananTeller•  Dr.OlgaKrichevsky•  Dr.SubramanianPalaniappan•  Dr.RameshSingh•  Dr.ManJunathaR.•  Dr.AleksKarajichPhDStudents•  Mrs.OritBen-Zazon•  SrikanthKolagatla•  HenFriman•  RoopathyMohan•  DiwakarKashyap•  AntonyCyrilMscStudents•  Mrs.MietalGor•  Mrs.YuliaYufa•  Mr.VictorMoltenan•  Miss.ShaniOchanuna•  Mr.YuvalMoshe•  Mr.AsafCohen•  Mrs.EfratTzor•  Mr.ShnmuelRozenfeld•  Mr.EtiPitossi•  Mr.LeaOaknin•  Mr.RazMasas•  Mr.YakirNagar•  Mr.MikeSasoon-Engineer

Collaborations • Dr. Daniel Nessim-BIU • Prof.-Yoed Tzur-Technion • Dr. David Zitoun-BIU • Dr. Amir Nathan-TAU • Dr. Rivka Cahan-AUC • Prof. Zeev Gross –Technion • Prof. Idit Avrahami-AUC • Prof. Steve Dubowsky -MIT • Prof. Edward Bormashenko –AUC • Prof. Haya Korenwitz-AUC • Prof. Aharon Gedanken-BIU • Dr. Flavio Grynszpan-AUC