New challenges of electrokinetic studies in investigating the reaction mechanism of electrochemical CO<sub>2</sub> reduction

Lee, Chan Woo; Cho, Nam Heon; Im, Sang Won; Jee, Michael Shincheon; Hwang, Yun Jeong; Min, Byoung Koun; Nam, Ki Tae

doi:10.1039/c8ta03480j

Cited by 135 publications

(100 citation statements)

References 85 publications

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“…NPC presented the smallest Tafel slope of 72 mV dec −1 (Figure a), suggesting the fastest kinetics of NPC, which was also confirmed by EIS (see Figure SI‐20). Moreover, this value was close to 59 mV dec −1 , implying that the rate‐determining step of ECDRR on NPC was no longer the first electron transfer to nonpolar CO 2 molecule to form bended *CO 2 .− , which was more likely to occur with difficulty on NC and PC for their Tafel slopes closer to 118 mV dec −1 . Moreover, electrolysis was conducted at a constant potential (vs RHE) with KHCO 3 concentration varying from 0.3 M to 0.03 M, in which the constant ionic strength was kept by NaClO 4 addition, to investigate whether HCO 3 − is a proton source for the rate‐determining proton transfer step in ECDRR on NPC.…”

Section: Resultsmentioning

confidence: 99%

Low‐Energy CO₂ Reduction on a Metal‐Free Carbon Material

et al. 2020

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Electrochemical CO 2 reduction to value-added chemicals on carbon-based catalysts is a potential approach for low-cost value-added CO 2 recycling. However, high overpotential and limited understanding of the mechanism remain challenging. Herein, a nitrogen and phosphorus co-doped carbon (NPC) material, which is synthesized through a simple pyrolysis, promoted low-energy electrochemical CO 2 reduction. The NPC electrocatalyst combines the advantages of active sites cooptimized by N and P, faster electrokinetics with bicarbonate providing proton, and more accessible active sites exposed by soft-template precursors. The NPC electrocatalyst exhibited more than ten-and fourfold enhancement of the partial current density of CO production compared to N-doped and P-doped carbon materials, respectively, with high selectivity (86 % faradaic efficiency) at only À 0.45 V. Experimental data coupled with density function theory calculations revealed that N and P dopants cooperated to enhance CO 2 adsorption, first electron transfer to CO 2 and then *COOH intermediate stabilization, leading to active and selective CO 2 -to-CO conversion. This work extends the design and understanding of metal-free carbonbased electrocatalysts for electrochemical CO 2 reduction.[a] Dr.adsorbates. The entropies of the free molecules were taken from the NIST database. [34][35][36] The solvent effect for stabilizing COOH* and CO* was 0.25 and 0.10 eV, respectively. [33] Due to the use of PBE functional, a further À 0.21 eV correction for the non-adsorbed gasphase CO molecule has been derived to accurately describe reaction free energy for CO 2 reduction to CO.

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Section: Resultsmentioning

confidence: 99%

Low‐Energy CO₂ Reduction on a Metal‐Free Carbon Material

et al. 2020

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“…First principles calculations and electro-kinetic modeling are highly insightful for efforts to decipher the CO 2 RR and identify the role of key intermediate species and elementary steps [255,259]. The microkinetic models usually ignore mass transport processes at the electrode level, thus assuming uniform reaction conditions [259,260].…”

Section: Modeling Electrochemical Co 2 Reductionmentioning

confidence: 99%

“…Changes in Tafel slope over a scanned range of electrode potential indicate that different elementary reaction steps and different reaction intermediates control the overall rate of the reaction; a particular value of the Tafel slope may thus be identified with a particular rate determining step or rate determining term in the multistep mechanism [52,116,264]. Moreover, the doubling of the Tafel slope could be indicative of the transition from a kinetically limited regime at low electrode overpotential to a mass transport-limited regime at high overpotential [255,261].…”

Section: Intermediates and Reaction Pathwaymentioning

confidence: 99%

Three-Dimensional Cathodes for Electrochemical Reduction of CO2: From Macro- to Nano-Engineering

et al. 2020

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Rising anthropogenic CO2 emissions and their climate warming effects have triggered a global response in research and development to reduce the emissions of this harmful greenhouse gas. The use of CO2 as a feedstock for the production of value-added fuels and chemicals is a promising pathway for development of renewable energy storage and reduction of carbon emissions. Electrochemical CO2 conversion offers a promising route for value-added products. Considerable challenges still remain, limiting this technology for industrial deployment. This work reviews the latest developments in experimental and modeling studies of three-dimensional cathodes towards high-performance electrochemical reduction of CO2. The fabrication–microstructure–performance relationships of electrodes are examined from the macro- to nanoscale. Furthermore, future challenges, perspectives and recommendations for high-performance cathodes are also presented.

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“…Specifically, products involving C-C bond formation (>C1) theoretically excluded to be possible on the Pt-based electrocatalyst used in these tests, can be instead formed with selectivity of about 60% by using a combination of reactor and electrode design aimed both to increase the effective surface concentration of CO 2 [87]. It was also shown recently that the conventional assumptions in electrokinetic studies (for example, related to Tafel plot) to derive a reaction mechanism in the reduction of CO 2 may not always be valid [88].…”

Section: Electrocatalysismentioning

confidence: 99%

Chemical engineering role in the use of renewable energy and alternative carbon sources in chemical production

2019

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There is a demand for new chemical reaction technologies and associated engineering aspects due to on-going transition in energy and chemistry associated to moving out progressively from the use of fossil fuels. Focus is given in this review on two main aspects: i) the development of alternative carbon sources and ii) the integration of renewable energy in the chemical production. It is shown how addressing properly these aspects requires to develop also a) new tools for chemical engineering assessment and b) innovative methodologies for the development of the materials, reactors and processes. This review evidences the need to accelerate studies on these directions, being a crucial element to catalyze the transition to a more sustainable use of energy and chemistry. It is remarked, however, the need to go beyond the traditional approaches, with some examples given. In fact, the presence of radical changes in the way of production is underlined, requiring thus novel fundamentals and applied engineering approaches.

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New challenges of electrokinetic studies in investigating the reaction mechanism of electrochemical CO₂ reduction

Abstract: New challenges for electrokinetic studies of CO2 reduction are addressed with the suggested reaction mechanisms of CO and HCOO− production.

Cited by 135 publications

References 85 publications

Low‐Energy CO₂ Reduction on a Metal‐Free Carbon Material

Low‐Energy CO₂ Reduction on a Metal‐Free Carbon Material

Three-Dimensional Cathodes for Electrochemical Reduction of CO2: From Macro- to Nano-Engineering

Chemical engineering role in the use of renewable energy and alternative carbon sources in chemical production

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New challenges of electrokinetic studies in investigating the reaction mechanism of electrochemical CO2 reduction

Abstract: New challenges for electrokinetic studies of CO2 reduction are addressed with the suggested reaction mechanisms of CO and HCOO− production.

Cited by 135 publications

References 85 publications

Low‐Energy CO2 Reduction on a Metal‐Free Carbon Material

Low‐Energy CO2 Reduction on a Metal‐Free Carbon Material

Three-Dimensional Cathodes for Electrochemical Reduction of CO2: From Macro- to Nano-Engineering

Chemical engineering role in the use of renewable energy and alternative carbon sources in chemical production

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New challenges of electrokinetic studies in investigating the reaction mechanism of electrochemical CO₂ reduction

Low‐Energy CO₂ Reduction on a Metal‐Free Carbon Material

Low‐Energy CO₂ Reduction on a Metal‐Free Carbon Material