1
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Yu H, Govindarajan N, Weitzner SE, Serra-Maia RF, Akhade SA, Varley JB. Theoretical Investigation of the Adsorbate and Potential-Induced Stability of Cu Facets During Electrochemical CO 2 and CO Reduction. Chemphyschem 2024; 25:e202300959. [PMID: 38409629 DOI: 10.1002/cphc.202300959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 02/06/2024] [Accepted: 02/21/2024] [Indexed: 02/28/2024]
Abstract
The activity and product selectivity of electrocatalysts for reactions like the carbon dioxide reduction reaction (CO2RR) are intimately dependent on the catalyst's structure and composition. While engineering catalytic surfaces can improve performance, discovering the key sets of rational design principles remains challenging due to limitations in modeling catalyst stability under operating conditions. Herein, we perform first-principles density functional calculations adopting implicit solvation methods with potential control to study the influence of adsorbates and applied potential on the stability of different facets of model Cu electrocatalysts. Using coverage dependencies extracted from microkinetic models, we describe an approach for calculating potential and adsorbate-dependent contributions to surface energies under reaction conditions, where Wulff constructions are used to understand the morphological evolution of Cu electrocatalysts under CO2RR conditions. We identify that CO*, a key reaction intermediate, exhibits higher kinetically and thermodynamically accessible coverages on (100) relative to (111) facets, which can translate into an increased relative stabilization of the (100) facet during CO2RR. Our results support the known tendency for increased (111) faceting of Cu nanoparticles under more reducing conditions and that the relative increase in (100) faceting observed under CO2RR conditions is likely attributed to differences in CO* coverage between these facets.
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Affiliation(s)
- Henry Yu
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Laboratory for Energy Applications for the Future, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Nitish Govindarajan
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Laboratory for Energy Applications for the Future, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Stephen E Weitzner
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Laboratory for Energy Applications for the Future, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Rui F Serra-Maia
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Sneha A Akhade
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Laboratory for Energy Applications for the Future, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Joel B Varley
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Laboratory for Energy Applications for the Future, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
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2
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Kim C, Govindarajan N, Hemenway S, Park J, Zoraster A, Kong CJ, Prabhakar RR, Varley JB, Jung HT, Hahn C, Ager JW. Importance of Site Diversity and Connectivity in Electrochemical CO Reduction on Cu. ACS Catal 2024; 14:3128-3138. [PMID: 38449526 PMCID: PMC10913037 DOI: 10.1021/acscatal.3c05904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/23/2024] [Accepted: 01/31/2024] [Indexed: 03/08/2024]
Abstract
Electrochemical CO2 reduction on Cu is a promising approach to produce value-added chemicals using renewable feedstocks, yet various Cu preparations have led to differences in activity and selectivity toward single and multicarbon products. Here, we find, surprisingly, that the effective catalytic activity toward ethylene improves when there is a larger fraction of less active sites acting as reservoirs of *CO on the surface of Cu nanoparticle electrocatalysts. In an adaptation of chemical transient kinetics to electrocatalysis, we measure the dynamic response of a gas diffusion electrode (GDE) cell when the feed gas is abruptly switched between Ar (inert) and CO. When switching from Ar to CO, CO reduction (COR) begins promptly, but when switching from CO to Ar, COR can be maintained for several seconds (delay time) despite the absence of the CO reactant in the gas phase. A three-site microkinetic model captures the observed dynamic behavior and shows that Cu catalysts exhibiting delay times have a less active *CO reservoir that exhibits fast diffusion to active sites. The observed delay times and the estimated *CO reservoir sizes are affected by catalyst preparation, applied potential, and microenvironment (electrolyte cation identity, electrolyte pH, and CO partial pressure). Notably, we estimate that the *CO reservoir surface coverage can be as high as 88 ± 7% on oxide-derived Cu (OD-Cu) at high overpotentials (-1.52 V vs SHE) and this increases in reservoir coverage coincide with increased turnover frequencies to ethylene. We also estimate that *CO can travel substantial distances (up to 10s of nm) prior to desorption or reaction. It appears that active C-C coupling sites by themselves do not control selectivity to C2+ products in electrochemical COR; the supply of CO to those sites is also a crucial factor. More generally, the overall activity of Cu electrocatalysts cannot be approximated from linear combinations of individual site activities. Future designs must consider the diversity of the catalyst network and account for intersite transportation pathways.
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Affiliation(s)
- Chansol Kim
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro,
Yuseong-gu, Daejeon 34141, South Korea
- Clean
Energy Research Center, Korea Institute
of Science and Technology (KIST), Seoul 02792, South Korea
| | - Nitish Govindarajan
- Materials
Science Division, Lawrence Livermore National
Laboratory, Livermore, California 94550, United States
| | - Sydney Hemenway
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, Berkeley, California 94720, United States
| | - Junho Park
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, Berkeley, California 94720, United States
| | - Anya Zoraster
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Chemical and Biochemical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Calton J. Kong
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, Berkeley, California 94720, United States
| | - Rajiv Ramanujam Prabhakar
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Joel B. Varley
- Materials
Science Division, Lawrence Livermore National
Laboratory, Livermore, California 94550, United States
| | - Hee-Tae Jung
- Department
of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro,
Yuseong-gu, Daejeon 34141, South Korea
| | - Christopher Hahn
- Materials
Science Division, Lawrence Livermore National
Laboratory, Livermore, California 94550, United States
| | - Joel W. Ager
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
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3
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Deng W, Zhang P, Qiao Y, Kastlunger G, Govindarajan N, Xu A, Chorkendorff I, Seger B, Gong J. Unraveling the rate-determining step of C 2+ products during electrochemical CO reduction. Nat Commun 2024; 15:892. [PMID: 38291057 PMCID: PMC10828390 DOI: 10.1038/s41467-024-45230-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 01/16/2024] [Indexed: 02/01/2024] Open
Abstract
The electrochemical reduction of CO has drawn a large amount of attention due to its potential to produce sustainable fuels and chemicals by using renewable energy. However, the reaction's mechanism is not yet well understood. A major debate is whether the rate-determining step for the generation of multi-carbon products is C-C coupling or CO hydrogenation. This paper conducts an experimental analysis of the rate-determining step, exploring pH dependency, kinetic isotope effects, and the impact of CO partial pressure on multi-carbon product activity. Results reveal constant multi-carbon product activity with pH or electrolyte deuteration changes, and CO partial pressure data aligns with the theoretical formula derived from *CO-*CO coupling as the rate-determining step. These findings establish the dimerization of two *CO as the rate-determining step for multi-carbon product formation. Extending the study to commercial copper nanoparticles and oxide-derived copper catalysts shows their rate-determining step also involves *CO-*CO coupling. This investigation provides vital kinetic data and a theoretical foundation for enhancing multi-carbon product production.
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Affiliation(s)
- Wanyu Deng
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300072, China
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou, 350207, China
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark
| | - Peng Zhang
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300072, China
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou, 350207, China
| | - Yu Qiao
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark
| | - Georg Kastlunger
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark
| | - Nitish Govindarajan
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark
| | - Aoni Xu
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark
| | - Ib Chorkendorff
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark
| | - Brian Seger
- Department of Physics, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark.
| | - Jinlong Gong
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300072, China.
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou, 350207, China.
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Liu S, Vijay S, Xu M, Cao A, Prats H, Kastlunger G, Heenen HH, Govindarajan N. Solvation of furfural at metal-water interfaces: Implications for aqueous phase hydrogenation reactions. J Chem Phys 2023; 159:084702. [PMID: 37606330 DOI: 10.1063/5.0157573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 06/21/2023] [Indexed: 08/23/2023] Open
Abstract
Metal-water interfaces are central to understanding aqueous-phase heterogeneous catalytic processes. However, the explicit modeling of the interface is still challenging as it necessitates extensive sampling of the interfaces' degrees of freedom. Herein, we use ab initio molecular dynamics (AIMD) simulations to study the adsorption of furfural, a platform biomass chemical on several catalytically relevant metal-water interfaces (Pt, Rh, Pd, Cu, and Au) at low coverages. We find that furfural adsorption is destabilized on all the metal-water interfaces compared to the metal-gas interfaces considered in this work. This destabilization is a result of the energetic penalty associated with the displacement of water molecules near the surface upon adsorption of furfural, further evidenced by a linear correlation between solvation energy and the change in surface water coverage. To predict solvation energies without the need for computationally expensive AIMD simulations, we demonstrate OH binding energy as a good descriptor to estimate the solvation energies of furfural. Using microkinetic modeling, we further explain the origin of the activity for furfural hydrogenation on intrinsically strong-binding metals under aqueous conditions, i.e., the endothermic solvation energies for furfural adsorption prevent surface poisoning. Our work sheds light on the development of active aqueous-phase catalytic systems via rationally tuning the solvation energies of reaction intermediates.
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Affiliation(s)
- Sihang Liu
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Sudarshan Vijay
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Mianle Xu
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Ang Cao
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Hector Prats
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
- Department of Chemical Engineering, University College London, Roberts Building, Torrington Place, London WC1E 7JE, United Kingdom
| | - Georg Kastlunger
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Hendrik H Heenen
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195, Germany
| | - Nitish Govindarajan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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5
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Liu S, Mukadam Z, Scott SB, Sarma SC, Titirici MM, Chan K, Govindarajan N, Stephens IEL, Kastlunger G. Unraveling the reaction mechanisms for furfural electroreduction on copper. EES Catal 2023; 1:539-551. [PMID: 37426696 PMCID: PMC10323714 DOI: 10.1039/d3ey00040k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 04/27/2023] [Indexed: 07/11/2023]
Abstract
Electrochemical routes for the valorization of biomass-derived feedstock molecules offer sustainable pathways to produce chemicals and fuels. However, the underlying reaction mechanisms for their electrochemical conversion remain elusive. In particular, the exact role of proton-electron coupled transfer and electrocatalytic hydrogenation in the reaction mechanisms for biomass electroreduction are disputed. In this work, we study the reaction mechanism underlying the electroreduction of furfural, an important biomass-derived platform chemical, combining grand-canonical (constant-potential) density functional theory-based microkinetic simulations and pH dependent experiments on Cu under acidic conditions. Our simulations indicate the second PCET step in the reaction pathway to be the rate- and selectivity-determining step for the production of the two main products of furfural electroreduction on Cu, i.e., furfuryl alcohol and 2-methyl furan, at moderate overpotentials. We further identify the source of Cu's ability to produce both products with comparable activity in their nearly equal activation energies. Furthermore, our microkinetic simulations suggest that surface hydrogenation steps play a minor role in determining the overall activity of furfural electroreduction compared to PCET steps due to the low steady-state hydrogen coverage predicted under reaction conditions, the high activation barriers for surface hydrogenation and the observed pH dependence of the reaction. As a theoretical guideline, low pH (<1.5) and moderate potential (ca. -0.5 V vs. SHE) conditions are suggested for selective 2-MF production.
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Affiliation(s)
- Sihang Liu
- Department of Physics, Catalysis Theory Center, Technical University of Denmark (DTU) 2800 Kgs. Lyngby Denmark
| | - Zamaan Mukadam
- Department of Materials, Royal School of Mines, Imperial College London London SW27 AZ England UK
| | - Soren B Scott
- Department of Materials, Royal School of Mines, Imperial College London London SW27 AZ England UK
| | - Saurav Ch Sarma
- Department of Chemical Engineering, Imperial College London London SW7 2AZ England UK
| | - Maria-Magdalena Titirici
- Department of Chemical Engineering, Imperial College London London SW7 2AZ England UK
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University Sendai Miyagi 980-8577 Japan
| | - Karen Chan
- Department of Physics, Catalysis Theory Center, Technical University of Denmark (DTU) 2800 Kgs. Lyngby Denmark
| | - Nitish Govindarajan
- Department of Physics, Catalysis Theory Center, Technical University of Denmark (DTU) 2800 Kgs. Lyngby Denmark
- Materials Science Division, Lawrence Livermore National Laboratory Livermore California 94550 USA
| | - Ifan E L Stephens
- Department of Materials, Royal School of Mines, Imperial College London London SW27 AZ England UK
| | - Georg Kastlunger
- Department of Physics, Catalysis Theory Center, Technical University of Denmark (DTU) 2800 Kgs. Lyngby Denmark
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6
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Kastlunger G, Heenen HH, Govindarajan N. Combining First-Principles Kinetics and Experimental Data to Establish Guidelines for Product Selectivity in Electrochemical CO 2 Reduction. ACS Catal 2023. [DOI: 10.1021/acscatal.3c00228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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7
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Liu S, Govindarajan N, Chan K. Understanding Activity Trends in Furfural Hydrogenation on Transition Metal Surfaces. ACS Catal 2022. [DOI: 10.1021/acscatal.2c03822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sihang Liu
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Nitish Govindarajan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
- Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Karen Chan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
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8
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Kastlunger G, Wang L, Govindarajan N, Heenen HH, Ringe S, Jaramillo T, Hahn C, Chan K. Using pH Dependence to Understand Mechanisms in Electrochemical CO Reduction. ACS Catal 2022. [DOI: 10.1021/acscatal.1c05520] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Georg Kastlunger
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Lei Wang
- SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States
- Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117585, Singapore
| | - Nitish Govindarajan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Hendrik H. Heenen
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
| | - Stefan Ringe
- Department of Energy Science and Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Republic of Korea
- Energy Science and Engineering Research Center, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841, Republic of Korea
| | - Thomas Jaramillo
- SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States
| | - Christopher Hahn
- SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Karen Chan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark
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Abstract
Electrochemical CO2 reduction (eCO2R) enables the conversion of waste CO2 to high-value fuels and commodity chemicals powered by renewable electricity, thereby offering a viable strategy for reaching the goal of net-zero carbon emissions. Research in the past few decades has focused both on the optimization of the catalyst (electrode) and the electrolyte environment. Surface-area normalized current densities show that the latter can affect the CO2 reduction activity by up to a few orders of magnitude.In this Account, we review theories of the mechanisms behind the effects of the electrolyte (cations, anions, and the electrolyte pH) on eCO2R. As summarized in the conspectus graphic, the electrolyte influences eCO2R activity via a field (ε) effect on dipolar (μ) reaction intermediates, changing the proton donor for the multi-step proton-electron transfer reaction, specifically adsorbed anions on the catalyst surface to block active sites, and tuning the local environment by homogeneous reactions. To be specific, alkali metal cations (M+) can stabilize reaction intermediates via electrostatic interactions with dipolar intermediates or buffer the interfacial pH via hydrolysis reactions, thereby promoting the eCO2R activity with the following trend in hydrated size (corresponding to the local field strength ε)/hydrolysis ability: Cs+ > K+ > Na+ > Li+. The effect of the electrolyte pH can give a change in eCO2R activity of up to several orders of magnitude, arising from linearly shifting the absolute interfacial field via the relationship USHE = URHE - (2.3kBT)pH, homogeneous reactions between OH- and desorbed intermediates, or changing the proton donor from hydronium to water along with increasing pH. Anions have been suggested to affect the eCO2R reaction process by solution-phase reactions (e.g., buffer reactions to tune local pH), acting as proton donors or as a surface poison.So far, the existing models of electrolyte effects have been used to rationalize various experimentally observed trends, having yet to demonstrate general predictive capabilities. The major challenges in our understanding of the electrolyte effect in eCO2R are (i) the long time scale associated with a dynamic ab initio picture of the catalyst|electrolyte interface and (ii) the overall activity determined by the length-scale interplay of intrinsic microkinetics, homogeneous reactions, and mass transport limitations. New developments in ab initio dynamic models and coupling the effects of mass transport can provide a more accurate view of the structure and intrinsic functions of the electrode-electrolyte interface and the corresponding reaction energetics toward comprehensive and predictive models for electrolyte design.
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Affiliation(s)
- Aoni Xu
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Nitish Govindarajan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Georg Kastlunger
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Sudarshan Vijay
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Karen Chan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
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10
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Abstract
[Figure: see text].
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Affiliation(s)
- Nitish Govindarajan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Aoni Xu
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Karen Chan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
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11
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Govindarajan N, Kastlunger G, Heenen HH, Chan K. Improving the intrinsic activity of electrocatalysts for sustainable energy conversion: where are we and where can we go? Chem Sci 2021; 13:14-26. [PMID: 35059146 PMCID: PMC8694373 DOI: 10.1039/d1sc04775b] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/14/2021] [Indexed: 12/19/2022] Open
Abstract
As we are in the midst of a climate crisis, there is an urgent need to transition to the sustainable production of fuels and chemicals. A promising strategy towards this transition is to use renewable energy for the electrochemical conversion of abundant molecules present in the earth's atmosphere such as H2O, O2, N2 and CO2, to synthetic fuels and chemicals. A cornerstone to this strategy is the development of earth abundant electrocatalysts with high intrinsic activity towards the desired products. In this perspective, we discuss the importance and challenges involved in the estimation of intrinsic activity both from the experimental and theoretical front. Through a thorough analysis of published data, we find that only modest improvements in intrinsic activity of electrocatalysts have been achieved in the past two decades which necessitates the need for a paradigm shift in electrocatalyst design. To this end, we highlight opportunities offered by tuning three components of the electrochemical environment: cations, buffering anions and the electrolyte pH. These components can significantly alter catalytic activity as demonstrated using several examples, and bring us a step closer towards complete system level optimization of electrochemical routes to sustainable energy conversion.
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Affiliation(s)
- Nitish Govindarajan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU) Fysikvej 311 2800 Kgs. Lyngby Denmark
| | - Georg Kastlunger
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU) Fysikvej 311 2800 Kgs. Lyngby Denmark
| | - Hendrik H Heenen
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU) Fysikvej 311 2800 Kgs. Lyngby Denmark .,Fritz-Haber-Institut der Max-Planck-Gesellschaft Faradayweg 4-6 D-14195 Berlin Germany
| | - Karen Chan
- Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU) Fysikvej 311 2800 Kgs. Lyngby Denmark
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12
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Affiliation(s)
- Nitish Govindarajan
- Amsterdam Center for Multiscale Modeling and Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
- Catalysis Theory Center, Department of Physics, Technical University of Denmark, 2800 Kongens, Lyngby, Denmark
| | - Hugo Beks
- Amsterdam Center for Multiscale Modeling and Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
| | - Evert Jan Meijer
- Amsterdam Center for Multiscale Modeling and Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
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13
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Govindarajan N, Sinha V, Trincado M, Grützmacher H, Meijer EJ, Bruin B. An In‐Depth Mechanistic Study of Ru‐Catalysed Aqueous Methanol Dehydrogenation and Prospects for Future Catalyst Design. ChemCatChem 2020. [DOI: 10.1002/cctc.202000057] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Nitish Govindarajan
- Van ‘t Hoff Institute for Molecular Sciences and Amsterdam Center for Multiscale Modeling Science Park 904 1098 XH Amsterdam The Netherlands
| | - Vivek Sinha
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Van ‘t Hoff Institute for Molecular Sciences Science Park 904 1098 XH Amsterdam The Netherlands
| | - Monica Trincado
- Department of Chemistry and Applied Biosciences ETH Zürich Zürich CH-8093 Switzerland
| | - Hansjörg Grützmacher
- Department of Chemistry and Applied Biosciences ETH Zürich Zürich CH-8093 Switzerland
| | - Evert Jan Meijer
- Van ‘t Hoff Institute for Molecular Sciences and Amsterdam Center for Multiscale Modeling Science Park 904 1098 XH Amsterdam The Netherlands
| | - Bas Bruin
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Van ‘t Hoff Institute for Molecular Sciences Science Park 904 1098 XH Amsterdam The Netherlands
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14
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Abstract
In this work, we use density functional theory based molecular dynamics with an explicit description of methanol solvent to study the effect of cations on formic acid dehydrogenation catalyzed by a ruthenium PNP pincer complex (RuPNP). Formic acid dehydrogenation is a two step process that involves the reorientation of the formate moiety bound via its oxygen to a H bound intermediate, followed by the hydride transfer step to form CO2 and the hydrogenated catalyst. We find the reorientation step to proceed with a low barrier in methanol solvent and in the presence of a Li+ cation, while the hydride transfer is significantly hindered by the presence of cations (Li+ and K+). The cation seems to strongly stabilize the negatively charged formate moiety, hindering complete hydride transfer and resulting in a high barrier for this step. This study is a first step towards addressing the exact role of cations in formic acid dehydrogenation reactions.
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Affiliation(s)
- Nitish Govindarajan
- Van't Hoff Institute for Molecular Sciences, Amsterdam Center for Multiscale Modeling, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
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Affiliation(s)
- Nitish Govindarajan
- Amsterdam Center for Multiscale Modeling and Van ’t Hoff Institute for Molecular Sciences, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Marc T. M. Koper
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Evert Jan Meijer
- Amsterdam Center for Multiscale Modeling and Van ’t Hoff Institute for Molecular Sciences, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Federico Calle-Vallejo
- Departament de Ciència de Materials i Química Fisica, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franqués 1, 08028 Barcelona, Spain
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Sinha V, Govindarajan N, de Bruin B, Meijer EJ. How Solvent Affects C-H Activation and Hydrogen Production Pathways in Homogeneous Ru-Catalyzed Methanol Dehydrogenation Reactions. ACS Catal 2018; 8:6908-6913. [PMID: 30101037 PMCID: PMC6080862 DOI: 10.1021/acscatal.8b01177] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 05/10/2018] [Indexed: 11/29/2022]
Abstract
Insights into the mechanism of the catalytic cycle for methanol dehydrogenation catalyzed by a highly active PNP pincer ruthenium complex in methanol solvent are presented, using DFT-based molecular dynamics with an explicit description of the solvent, as well as static DFT calculations using microsolvation models. In contrast to previous results, we find the amido moiety of the catalyst to be permanently protonated under catalytic conditions. Solvent molecules actively participate in crucial reaction steps and significantly affect the reaction barriers when compared to pure gas-phase models, which is a direct result of the enhanced solvent stabilization of methoxide anion intermediates. Further, the calculations reveal that this system does not operate via the commonly assumed Noyori-type outer-sphere metal-ligand cooperative pathway. Our results show the importance of incorporating a molecular description of the solvent to gain a deeper and accurate understanding of the reaction pathways, and stress on the need to involve explicit solvent molecules to model complex catalytic processes in a realistic manner.
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Affiliation(s)
- Vivek Sinha
- Homogenous, Supramolecular and Bio-Inspired Catalysis, Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Nitish Govindarajan
- Amsterdam Center for Multiscale Modeling and Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Bas de Bruin
- Homogenous, Supramolecular and Bio-Inspired Catalysis, Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Evert Jan Meijer
- Amsterdam Center for Multiscale Modeling and Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
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Govindarajan N, Tiwari A, Ensing B, Meijer EJ. Impact of the Ligand Flexibility and Solvent on the O-O Bond Formation Step in a Highly Active Ruthenium Water Oxidation Catalyst. Inorg Chem 2018; 57:13063-13066. [PMID: 29732882 PMCID: PMC6220359 DOI: 10.1021/acs.inorgchem.8b00619] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
By advanced molecular dynamics simulations, we show that for a highly active ruthenium-based water oxidation catalyst the dangling carboxylate group of the catalyst plays an important role in the crucial O-O bond formation step. The interplay of the flexible group and solvent molecules facilitates two possible pathways: a direct pathway with a single solvent water molecule or a mediated pathway involving two solvent water molecules, which have similar activation barriers. Our results provide an example for which a realistic molecular dynamics approach, incorporating an explicit description of the solvent, is required to reveal the full complexity of an important catalytic reaction in aqueous solvent.
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Affiliation(s)
- Nitish Govindarajan
- Amsterdam Center for Multiscale Modeling and Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098XH Amsterdam , The Netherlands
| | - Ambuj Tiwari
- Amsterdam Center for Multiscale Modeling and Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098XH Amsterdam , The Netherlands
| | - Bernd Ensing
- Amsterdam Center for Multiscale Modeling and Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098XH Amsterdam , The Netherlands
| | - Evert Jan Meijer
- Amsterdam Center for Multiscale Modeling and Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098XH Amsterdam , The Netherlands
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Govindarajan N, Nazaryan V, Gueye P, Keppel C. SU-GG-T-49: Real Time Dose Verification for Novel Shielded Balloon Brachytherapy. Med Phys 2010. [DOI: 10.1118/1.3468435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Govindarajan N, Nazaryan V, Keppel C, Gueye P. SU-FF-T-19: Accelerated Partial Breast Irradiation With Shielded MammoSite-Type Applicator. Med Phys 2009. [DOI: 10.1118/1.3181490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Govindarajan N, Meiyappan S, Prakash O. Real-time respiratory monitoring workstation--software and hardware engineering aspects. Int J Clin Monit Comput 1992; 9:141-8. [PMID: 1447536 DOI: 10.1007/bf01145166] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have applied advanced real-time techniques in software, that are intensively used in critical areas like space research and defence applications, to realise an Integrated Real-Time Respiratory Monitoring System at the Thorax Anesthesiology, Academic Hospital Rotterdam. The system is called the 'SERVO WINDOW'--a window to the servo ventilator. The heart of the system is a real-time kernel that uses preemptive scheduling to achieve multitasking on a IBM PC compatible hardware platform. To the clinician this means that he gets all relevant information from one source i.e. the Respiratory Workstation. The waveforms of the airway pressure, airway flow and the expired CO2 curve are displayed continuously on the screen. The Vector Loops like Pressure Volume, Flow Pressure and Flow Volume loops are also available in addition to the lung mechanics parameters like Expiratory and Inspiratory Resistances, Compliances, Peak Pressure, PEEP, etc. The Single Breath Diagram i.e. expired CO2 concentration versus volume and dead space ventilation is also calculated. The blood gas analysis data is plotted in convenient diagrams like the O2-CO2 diagram, Oxygen Chart, etc. The trend of all these parameters are available with a granularity of one minute. An industry standard laser printer is used for report generation to produce reports of the real-time waveforms, parameter values and the trends. User interface is through easy menus with the traditional keyboard, touchscreen including keyboard on screen for data entry and the mouse.
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Abstract
An algorithm for the detection and delineation of breaths is described. The proposed algorithm takes into account the different, common modes of ventilation like the pressure controlled, volume controlled and patient triggered modes of ventilation. Airway flow curve is used as the basic delineator and the airway pressure and the Co2 concentration curves are used to confirm the delineation. A flow chart is also included to explain the algorithm. The detailed explanation and modifications, for additional confirmation and for the selections of constants, to check for the rise or fall of the pressure and Co2 curves, are also included.
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Affiliation(s)
- N Govindarajan
- Thorax Centrum, Erasmus University, Rotterdam, The Netherlands
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