Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolysers

Endrődi, Balázs; Samu, A.; Kecsenovity, Egon; Halmágyi, Tibor; Sebők, Dániel; Janáky, Cs.

doi:10.1038/s41560-021-00813-w

Cited by 235 publications

(332 citation statements)

References 47 publications

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“…This further confirms that carbonate ions are the dominant charge carriers between the electrodes. 3 , 39 The anodically formed protons neutralize stoichiometric amounts of the alkaline anolyte, ultimately liberating CO 2 once the pH becomes low enough (see further details in the Supporting Information , section 2.1). The gas flow rate is ∼3.2–3.4 cm 3 min –1 when the cathode is fed with Ar gas using either Ir or Ni as anode (i.e., HER proceeds at the cathode), correlating with the value calculated from Faraday’s law (3.4 cm 3 min –1 ).…”

Section: Comparing the Operation Of A Zero-gap Co 2 Electrolyzer Cell Using Ir And Ni Anode Catalystsmentioning

confidence: 99%

Local Chemical Environment Governs Anode Processes in CO₂ Electrolyzers

et al. 2021

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A major goal within the CO 2 electrolysis community is to replace the generally used Ir anode catalyst with a more abundant material, which is stable and active for water oxidation under process conditions. Ni is widely applied in alkaline water electrolysis, and it has been considered as a potential anode catalyst in CO 2 electrolysis. Here we compare the operation of electrolyzer cells with Ir and Ni anodes and demonstrate that, while Ir is stable under process conditions, the degradation of Ni leads to a rapid cell failure. This is caused by two parallel mechanisms: (i) a pH decrease of the anolyte to a near neutral value and (ii) the local chemical environment developing at the anode (i.e., high carbonate concentration). The latter is detrimental for zero-gap electrolyzer cells only, but the first mechanism is universal, occurring in any kind of CO 2 electrolyzer after prolonged operation with recirculated anolyte.

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Section: Comparing the Operation Of A Zero-gap Co 2 Electrolyzer Cell Using Ir And Ni Anode Catalystsmentioning

confidence: 99%

Local Chemical Environment Governs Anode Processes in CO₂ Electrolyzers

et al. 2021

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“…However, most of the studies were performed in alkaline conditions, but it is possible to obtain relatively high FEs for CO in slightly acidic or near-neutral conditions and in membrane electrode assembly (MEA) based cells. 79 − 81 An alternative technology, based on a solid oxide electrochemical cell (SOEC), has been developed and commercialized by Haldor Topsoe to convert CO 2 to CO, which has a claimed energy requirement of 6–8 kWh/Nm 3 CO. 82 Furthermore, many industrial (purge) streams already contain substantial amounts of CO, which can be utilized (after purification) in the second step of the process. Note that it is crucial to have a high conversion of CO 2 in the first step.…”

Section: State Of the Art Of Co2r And Cor To C 2+ Productsmentioning

confidence: 99%

Electroreduction of CO₂/CO to C₂ Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis

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Morrison

et al. 2021

Ind. Eng. Chem. Res.

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Direct electrochemical reduction of CO 2 to C 2 products such as ethylene is more efficient in alkaline media, but it suffers from parasitic loss of reactants due to (bi)carbonate formation. A two-step process where the CO 2 is first electrochemically reduced to CO and subsequently converted to desired C 2 products has the potential to overcome the limitations posed by direct CO 2 electroreduction. In this study, we investigated the technical and economic feasibility of the direct and indirect CO 2 conversion routes to C 2 products. For the indirect route, CO 2 to CO conversion in a high temperature solid oxide electrolysis cell (SOEC) or a low temperature electrolyzer has been considered. The product distribution, conversion, selectivities, current densities, and cell potentials are different for both CO 2 conversion routes, which affects the downstream processing and the economics. A detailed process design and techno-economic analysis of both CO 2 conversion pathways are presented, which includes CO 2 capture, CO 2 (and CO) conversion, CO 2 (and CO) recycling, and product separation. Our economic analysis shows that both conversion routes are not profitable under the base case scenario, but the economics can be improved significantly by reducing the cell voltage, the capital cost of the electrolyzers, and the electricity price. For both routes, a cell voltage of 2.5 V, a capital cost of $10,000/m 2 , and an electricity price of <$20/MWh will yield a positive net present value and payback times of less than 15 years. Overall, the high temperature (SOEC-based) two-step conversion process has a greater potential for scale-up than the direct electrochemical conversion route. Strategies for integrating the electrochemical CO 2 /CO conversion process into the existing gas and oil infrastructure are outlined. Current barriers for industrialization of CO 2 electrolyzers and possible solutions are discussed as well.

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“…In a recent example, Endrődi et al mixed the inputted CO 2 gas feed with alkali-cation containing solutions as a way to improve the cation concentration at the catalyst surface in a MEA cell with a pure water anolyte. 17 With this treatment, ECO2R to CO reached several times higher activity than without any treatment, although it required repeat implementation. Other solutions could be coating the catalyst layer with an ionomer that has suitable cation groups in favor of ECO2R.…”

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“… 24 − 28 Combining these observations with previous BPMEA demonstrations that have traditionally suffered from poor CO 2 reduction selectivities, we hypothesized that the low selectivity in a BPMEA system could be overcome by increasing cation concentrations at the cathode. 17 , 18 , 27 Thus, if the low parasitic CO 2 loss of BPM’s can be achieved simultaneously with improved CO 2 reduction performance, high CO 2 utilization efficiencies would be possible as a result.…”

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Cation-Driven Increases of CO₂ Utilization in a Bipolar Membrane Electrode Assembly for CO₂ Electrolysis

et al. 2021

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Advancing reaction rates for electrochemical CO 2 reduction in membrane electrode assemblies (MEAs) have boosted the promise of the technology while exposing new shortcomings. Among these is the maximum utilization of CO 2 , which is capped at 50% (CO as targeted product) due to unwanted homogeneous reactions. Using bipolar membranes in an MEA (BPMEA) has the capability of preventing parasitic CO 2 losses, but their promise is dampened by poor CO 2 activity and selectivity. In this work, we enable a 3-fold increase in the CO 2 reduction selectivity of a BPMEA system by promoting alkali cation (K + ) concentrations on the catalyst’s surface, achieving a CO Faradaic efficiency of 68%. When compared to an anion exchange membrane, the cation-infused bipolar membrane (BPM) system shows a 5-fold reduction in CO 2 loss at similar current densities, while breaking the 50% CO 2 utilization mark. The work provides a combined cation and BPM strategy for overcoming CO 2 utilization issues in CO 2 electrolyzers.

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Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolysers

Abstract: After longer operation of a zero-gap electrolyser cell (Fig. 1a and Supplementary Fig. 1) with alkaline anolyte, salt precipitates at the cathode, gradually decreasing its performance 24,25,29 . We also experienced this phenomenon (Supplementary Note 1

Cited by 235 publications

References 47 publications

Local Chemical Environment Governs Anode Processes in CO₂ Electrolyzers

Local Chemical Environment Governs Anode Processes in CO₂ Electrolyzers

Electroreduction of CO₂/CO to C₂ Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis

Cation-Driven Increases of CO₂ Utilization in a Bipolar Membrane Electrode Assembly for CO₂ Electrolysis

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Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolysers

Abstract: After longer operation of a zero-gap electrolyser cell (Fig. 1a and Supplementary Fig. 1) with alkaline anolyte, salt precipitates at the cathode, gradually decreasing its performance 24,25,29 . We also experienced this phenomenon (Supplementary Note 1

Cited by 235 publications

References 47 publications

Local Chemical Environment Governs Anode Processes in CO2 Electrolyzers

Local Chemical Environment Governs Anode Processes in CO2 Electrolyzers

Electroreduction of CO2/CO to C2 Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis

Cation-Driven Increases of CO2 Utilization in a Bipolar Membrane Electrode Assembly for CO2 Electrolysis

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Product

Resources

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Local Chemical Environment Governs Anode Processes in CO₂ Electrolyzers

Local Chemical Environment Governs Anode Processes in CO₂ Electrolyzers

Electroreduction of CO₂/CO to C₂ Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis

Cation-Driven Increases of CO₂ Utilization in a Bipolar Membrane Electrode Assembly for CO₂ Electrolysis