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Selective Electrochemical Reductive Amination of Benzaldehyde at Heterogeneous Metal Surfaces

Schiffer, Zachary J. and Chung, Minju and Steinberg, Katherine and Manthiram, Karthish (2022) Selective Electrochemical Reductive Amination of Benzaldehyde at Heterogeneous Metal Surfaces. . (Unpublished)

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Ammonia is one of the largest volume commodity chemicals, and electrochemical routes to ammonia utilization are appealing due to increasingly available renewable electricity. In this work, we demonstrate an electrochemical analogue to reductive amination for the synthesis of benzylamine from benzaldehyde and ammonia. Previous works on electrochemical reductive amination generally focus on proof-of-concept outer-sphere routes. We demonstrate an inner-sphere route, opening a large phase space of heterogeneous electrocatalysts that can direct selectivity and drive the reaction. In our system, imine hydrogenation proceeds on a silver electrocatalyst at ambient conditions in methanol with an initial Faradaic efficiency toward the primary amine product of ~80% and partial current greater than 4 mA/cm² at -1.96 V vs. Fc/Fc⁺ (-1.36 V vs. NHE). Silver was selected after evaluating diverse transition metal electrocatalysts, and with density functional theory, we found that the reaction rate on various metals is best described by the charge density distribution above the metal surface, independent of molecular adsorption energies. On silver, the catalyst that promotes amination with the highest Faradaic efficiency and one of the highest partial currents, the rate-determining step was found to be the initial electron transfer to the imine. Overall, this work on the kinetics of electrochemical reductive amination represents a step toward inner-sphere electrochemical reductive amination systems for the synthesis of amines that currently rely on thermochemical reductive amination.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Schiffer, Zachary J.0000-0001-6069-8613
Chung, Minju0000-0003-4359-7508
Steinberg, Katherine0000-0002-8232-7714
Manthiram, Karthish0000-0001-9260-3391
Additional Information:The content is available under CC BY NC ND 4.0 License. This material is based on work supported by the National Science Foundation under Grant No. 1944007. The authors thank Nathan Corbin, Nikifar Lazouski, and Kindle Williams for useful discussions. The authors also thank Andrew Medford, Ben Comer, Robert Warburton, and Aditya Nandy for help with DFT. ZJS and KS also acknowledges a graduate research fellowship from the National Science Foundation under Grant No. 1745302. ZJS acknowledges funding from Chevron through the MIT Energy Initiative. The authors acknowledge the MIT SuperCloud and Lincoln Laboratory Supercomputing Center for providing HPC resources that have contributed to the research results reported within this paper. Author Contributions: Conceptualization, Z.J.S. and K.M.; Resources, Z.J.S. and K.M.; Data curation, Z.J.S.; Software, Z.J.S.; Formal Analysis, Z.J.S.; Supervision, Z.J.S. and K.M.; Funding acquisition, Z.J.S. and K.M.; Validation, Z.J.S. and M.C.; Investigation, Z.J.S.; Visualization, Z.J.S.; Methodology, Z.J.S. and K.M.; Writing – original draft, Z.J.S.; Writing – review & editing, Z.J.S., M.C., K.S., K.M.; Project administration, Z.J.S. and K.M. Data Availability. All raw data and analysis scripts will be available upon request to the corresponding author. There are no competing interests to declare.
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1745302
Subject Keywords:Electrocatalysis; Reductive Amination; Heterogeneous Catalysis; Ammonia; Electrochemical Manufacturing
Record Number:CaltechAUTHORS:20220505-564477000
Persistent URL:
Official Citation:Schiffer Z, Chung M, Steinberg K, Manthiram K. Selective Electrochemical Reductive Amination of Benzaldehyde at Heterogeneous Metal Surfaces. ChemRxiv. 2022. doi:10.26434/chemrxiv-2022-2s2z7
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114604
Deposited By: George Porter
Deposited On:06 May 2022 16:07
Last Modified:06 May 2022 16:07

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