CO<sub>2</sub>Electrolysis to CO and O<sub>2</sub>at High Selectivity, Stability and Efficiency Using Sustainion Membranes

Liu, Zengcai; Yang, Hongzhou; Kutz, Robert; Masel, Richard I.

doi:10.1149/2.0501815jes

Cited by 229 publications

(258 citation statements)

References 47 publications

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“…The ratio of polymer to silver was 20%. This differs from values suggested in literature, [ 33,34 ] in an unsuccessful effort to maximize the visibility of the ionomer in the reconstruction. The GDE being specifically prepared for a tomographic study; it was not optimized for performance.…”

Section: Methodscontrasting

confidence: 76%

Tomographic Reconstruction and Analysis of a Silver CO₂ Reduction Cathode

McLaughlin

Bierling

Moroni

et al. 2020

Advanced Energy Materials

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electrochemical CO 2 RR enables direct power-to-X technology, that is the integration of electricity from (intermittent) renewable sources into the formation process of various valuable products. Technoeconomic analyses of CO 2 electrolyzers have identified current density and energy efficiency as the key benchmarks of this technology. [1][2][3][4][5] They further estimate that for adoption of this technology high current densities (hundreds of mA cm − ² or more) are required. The current density of the batch cells, which are ubiquitous in CO 2 RR catalyst research, is intrinsically limited. This points to flow cells with gas diffusion electrodes (GDEs) as a more promising solution. Endrődi et al. [6] and Weekes et al. [7] provide reviews of publications on flow cells using GDEs. Both highlight how flow cells and GDEs enable the aforementioned increase in current density and energy efficiency. Further recent publications demonstrate high current densities using GDEs. [8][9][10] The morphology of these electrodes is likely instrumental to their outstanding properties.Polymer electrolyte fuel cells (PEMFCs) and polymer electrolyte water electrolyzers (PEMWEs) serve as models for CO 2 electrolyzers, having achieved current densities in excess of amperes per square centimeter using GDE-based electrodes. [11][12][13][14] We suggest that if we wish to emulate the high current densities found in PEWMEs or PEMFCs, we need to understand the structure of CO 2 RR GDEs to subsequently improve it. Especially, we need to understand how the structure-property relations are similar and different from those found in PEMFCs and PEMWEs. This understanding in turn would enable rational design of catalyst layers (CLs), thus guiding the optimization of the manufacturing processes.To give an example: A point of discussion in some recent publications and perspectives has been the nature of the CO 2 delivery to the catalyst. Following the successful demonstration of GDEs application for CO 2 reduction, Cook et al. proposed a three-phase boundary mechanism according to which CO 2 reacts directly from the gas phase. [15] This model has been called into question. Burdyny and Smith [16] posit that the CL is fully flooded during operation; Weng et al. [17] propose that a thin layer of electrolyte covers the catalyst surface, in analogy to ionomer coverages often found in fuel cell models. This again points to the need for an improved understanding of electrode structure, especially its wetting behavior.Tomographic reconstruction has been well established as a valuable tool in the analysis of polymer electrolyte fuel cell (PEMFC) electrodes. While forays have been made into applying it to polymer electrolyte water electrolyzer (PEMWE) electrodes, CO 2 electrolyzer electrodes are still new ground. Here a tomographic analysis of an electrochemical CO 2 reduction gas diffusion electrode by means of focused ion beam scanning electron microscope tomography is presented. The reconstruction shows a porosity of 68%. While most of the porosity is on th...

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Section: Methodscontrasting

confidence: 76%

Tomographic Reconstruction and Analysis of a Silver CO₂ Reduction Cathode

McLaughlin

Bierling

Moroni

et al. 2020

Advanced Energy Materials

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“…We employed the electrochemical reduction of CO 2 to CO on Ag as a model reaction owing to its high selectivity, gaseous reactants/products, and robustness across multiple catalysts and cell configurations . We evaluated catalyst‐coated Freudenberg GDLs in a custom‐built, gas‐fed electrolyzer with a flowing electrolyte (Figure ).…”

Section: Resultsmentioning

confidence: 80%

“…In this configuration, the higher diffusivity of gaseous CO 2 (≈10 −1 cm 2 s −1 ) and the reduced diffusion lengths within the CL enable increased current densities, typically an order of magnitude or greater over atmospheric aqueous‐phase cell designs . Indeed, gas‐fed devices have demonstrated high geometric‐area‐specific current densities with a variety of CO‐ and hydrocarbon‐selective metal electrocatalysts . However, most emerging gas‐fed CO 2 electrolyzers often exhibit limited durability, with performance decay after only a few hours of operation, in part because these cell formats employ GDEs based on repurposed polymer electrolyte fuel cell (PEFC) materials that are not tailored to electrolysis applications.…”

Section: Introductionmentioning

confidence: 99%

Investigating Electrode Flooding in a Flowing Electrolyte, Gas‐Fed Carbon Dioxide Electrolyzer

et al. 2019

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Managing the gas–liquid interface within gas‐diffusion electrodes (GDEs) is key to maintaining high product selectivities in carbon dioxide electroreduction. By screening silver‐catalyzed GDEs over a range of applied current densities, an inverse correlation was observed between carbon monoxide selectivity and the electrochemical double‐layer capacitance, a proxy for wetted electrode area. Plotting current‐dependent performance as a function of cumulative charge led to data collapse onto a single sigmoidal curve indicating that the passage of faradaic current accelerates flooding. It was hypothesized that high cathode alkalinity, driven by both initial electrolyte conditions and cathode half‐reactions, promotes carbonate formation and precipitation which, in turn, facilitates electrolyte permeation. This mechanism was reinforced by the observations that post‐test GDEs retain less hydrophobicity than pristine materials and that water‐rinsing and drying electrodes temporarily recovers peak selectivity. This knowledge offers an opportunity to design electrodes with greater carbonation tolerance to improve device longevity.

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“…In fact, noble metals nanoparticles supported on carbon black are the catalysts of the most advanced electrolysers for gas-phase electro-reduction approaching a pilot demonstration phase [17,32,33]. Novel nanocarbon materials show in general modest results in terms of productivity.…”

Section: Conclusion and Future Prospectsmentioning

confidence: 99%

“…Potentiometric electrolysis in gas phase at a fixed current of 200 mAcm −2 showed that 98% selectivity could be maintained at about 3 V voltage for five months, with a voltage increase of only 3 µV/hour. The improved performance was attributed to the extended three phase boundaries in Ag cathode [33]. These orders of magnitude of current densities are already meaningful for industrial deployment.…”

Section: Introductionmentioning

confidence: 95%

Carbon Materials as Cathode Constituents for Electrochemical CO2 Reduction—A Review

Messias

Ponte

Machado

2019

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This work reviews the latest developments of cathodes for electrochemical CO 2 reduction, with carbon black, mesoporous carbons, carbon nanofibers, graphene, its derivatives and/or carbon nanotubes as constituents. Electrochemical CO 2 reduction into fuels and chemicals powered by renewable energy is a technology that can contribute to climate change mitigation. Strategies used in this fast-evolving field are discussed, having in mind a commercial application. Electrochemical performance of several materials is analyzed, using in some cases the findings of theoretical computational studies, which show the enormous potential of these materials. Considerable challenges still lie ahead to bring this technology into industrial deployment. However, the significant progress achieved so far shows that further R&D efforts might pay off.C 2019, 5, 83 2 of 26 considering the findings of theoretical computational studies, are in some cases analyzed, when this type of study is available. Knowledge gaps and new promising R&D trends of nanocarbon-based materials development for this application are highlighted. Carbon BlackCarbon black is produced by the incomplete combustion of petroleum heavy fractions. It is a form of para-crystalline carbon of high surface area. Although activated carbon has a more favorable surface area to volume ratio (>1000 m 2 /g) than carbon black, its low electrical conductivity makes it unsuitable as electrode material. Commercial carbon blacks, such as Vulcan or Ketjen black have been most frequently used as support to ensure large electrochemical reaction surfaces and to reduce noble metal loading. Metal and Metal-Derived Particles Supported on Carbon BlackCO 2 ER can be carried out in gas phase, where gaseous CO 2 is fed to the cathode through gas diffusion electrodes (GDE), or in liquid phase, where CO 2 dissolved in the liquid electrolyte contacts the electrode. Figure 1 presents a schematic diagram of two possible configurations of both operation modes.C 2019, 5, x FOR PEER REVIEW 2 of 25 discussed, having in mind a commercial application. Electrochemical performances of several materials, considering the findings of theoretical computational studies, are in some cases analyzed, when this type of study is available. Knowledge gaps and new promising R&D trends of nanocarbonbased materials development for this application are highlighted. Carbon BlackCarbon black is produced by the incomplete combustion of petroleum heavy fractions. It is a form of para-crystalline carbon of high surface area. Although activated carbon has a more favorable surface area to volume ratio (>1000 m 2 /g) than carbon black, its low electrical conductivity makes it unsuitable as electrode material. Commercial carbon blacks, such as Vulcan or Ketjen black have been most frequently used as support to ensure large electrochemical reaction surfaces and to reduce noble metal loading. Metal and Metal-Derived Particles Supported on Carbon BlackCO2ER can be carried out in gas phase, where gaseous CO2 is fed to the cathode thro...

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CO₂Electrolysis to CO and O₂at High Selectivity, Stability and Efficiency Using Sustainion Membranes

Cited by 229 publications

References 47 publications

Tomographic Reconstruction and Analysis of a Silver CO₂ Reduction Cathode

Tomographic Reconstruction and Analysis of a Silver CO₂ Reduction Cathode

Investigating Electrode Flooding in a Flowing Electrolyte, Gas‐Fed Carbon Dioxide Electrolyzer

Carbon Materials as Cathode Constituents for Electrochemical CO2 Reduction—A Review

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CO2Electrolysis to CO and O2at High Selectivity, Stability and Efficiency Using Sustainion Membranes

Cited by 229 publications

References 47 publications

Tomographic Reconstruction and Analysis of a Silver CO2 Reduction Cathode

Tomographic Reconstruction and Analysis of a Silver CO2 Reduction Cathode

Investigating Electrode Flooding in a Flowing Electrolyte, Gas‐Fed Carbon Dioxide Electrolyzer

Carbon Materials as Cathode Constituents for Electrochemical CO2 Reduction—A Review

Contact Info

Product

Resources

About

CO₂Electrolysis to CO and O₂at High Selectivity, Stability and Efficiency Using Sustainion Membranes

Tomographic Reconstruction and Analysis of a Silver CO₂ Reduction Cathode

Tomographic Reconstruction and Analysis of a Silver CO₂ Reduction Cathode