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Title: Directing the reactivity of metal hydrides for selective CO 2 reduction

Abstract

A critical challenge in electrocatalytic CO 2 reduction to renewable fuels is product selectivity. Desirable products of CO 2 reduction require proton equivalents, but key catalytic intermediates can also be competent for direct proton reduction to H 2 . Understanding how to manage divergent reaction pathways at these shared intermediates is essential to achieving high selectivity. Both proton reduction to hydrogen and CO 2 reduction to formate generally proceed through a metal hydride intermediate. We apply thermodynamic relationships that describe the reactivity of metal hydrides with H + and CO 2 to generate a thermodynamic product diagram, which outlines the free energy of product formation as a function of proton activity and hydricity (∆G H− ), or hydride donor strength. The diagram outlines a region of metal hydricity and proton activity in which CO 2 reduction is favorable and H + reduction is suppressed. We apply our diagram to inform our selection of [Pt(dmpe) 2 ](PF 6 ) 2 as a potential catalyst, because the corresponding hydride [HPt(dmpe) 2 ] + has the correct hydricity to access the region where selective CO 2 reduction is possible. We validate our choice experimentally; [Pt(dmpe) 2 ](PF 6 ) 2 is a highlymore » selective electrocatalyst for CO 2 reduction to formate (>90% Faradaic efficiency) at an overpotential of less than 100 mV in acetonitrile with no evidence of catalyst degradation after electrolysis. Our report of a selective catalyst for CO 2 reduction illustrates how our thermodynamic diagrams can guide selective and efficient catalyst discovery.« less

Authors:
; ORCiD logo
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1483024
Grant/Contract Number:  
SC0012150
Resource Type:
Journal Article: Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 115 Journal Issue: 50; Journal ID: ISSN 0027-8424
Publisher:
Proceedings of the National Academy of Sciences
Country of Publication:
United States
Language:
English

Citation Formats

Ceballos, Bianca M., and Yang, Jenny Y.. Directing the reactivity of metal hydrides for selective CO 2 reduction. United States: N. p., 2018. Web. doi:10.1073/pnas.1811396115.
Ceballos, Bianca M., & Yang, Jenny Y.. Directing the reactivity of metal hydrides for selective CO 2 reduction. United States. doi:10.1073/pnas.1811396115.
Ceballos, Bianca M., and Yang, Jenny Y.. Wed . "Directing the reactivity of metal hydrides for selective CO 2 reduction". United States. doi:10.1073/pnas.1811396115.
@article{osti_1483024,
title = {Directing the reactivity of metal hydrides for selective CO 2 reduction},
author = {Ceballos, Bianca M. and Yang, Jenny Y.},
abstractNote = {A critical challenge in electrocatalytic CO 2 reduction to renewable fuels is product selectivity. Desirable products of CO 2 reduction require proton equivalents, but key catalytic intermediates can also be competent for direct proton reduction to H 2 . Understanding how to manage divergent reaction pathways at these shared intermediates is essential to achieving high selectivity. Both proton reduction to hydrogen and CO 2 reduction to formate generally proceed through a metal hydride intermediate. We apply thermodynamic relationships that describe the reactivity of metal hydrides with H + and CO 2 to generate a thermodynamic product diagram, which outlines the free energy of product formation as a function of proton activity and hydricity (∆G H− ), or hydride donor strength. The diagram outlines a region of metal hydricity and proton activity in which CO 2 reduction is favorable and H + reduction is suppressed. We apply our diagram to inform our selection of [Pt(dmpe) 2 ](PF 6 ) 2 as a potential catalyst, because the corresponding hydride [HPt(dmpe) 2 ] + has the correct hydricity to access the region where selective CO 2 reduction is possible. We validate our choice experimentally; [Pt(dmpe) 2 ](PF 6 ) 2 is a highly selective electrocatalyst for CO 2 reduction to formate (>90% Faradaic efficiency) at an overpotential of less than 100 mV in acetonitrile with no evidence of catalyst degradation after electrolysis. Our report of a selective catalyst for CO 2 reduction illustrates how our thermodynamic diagrams can guide selective and efficient catalyst discovery.},
doi = {10.1073/pnas.1811396115},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 50,
volume = 115,
place = {United States},
year = {Wed Nov 21 00:00:00 EST 2018},
month = {Wed Nov 21 00:00:00 EST 2018}
}

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Works referenced in this record:

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