Capture and electrochemical conversion of CO<sub>2</sub> in molten alkali metal borate–carbonate blends

Bromberg, Lev; Nitzsche, Michael; Hatton, T. Alan

doi:10.1039/d2nr03355k

Cited by 15 publications

(13 citation statements)

References 72 publications

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“…As shown in the Raman spectrum (Figure f), the noticeable G band and 2D band located at 1580 and 2700 cm –1 , respectively, further reveal that the carbon nanocoils deliver graphitic features. Similar one-dimensional nanostructured carbon nanofibers/nanotubes can also be found in borate-containing and Li 2 O-containing lithium carbonates. − Considering that the oxygen content of carbonaceous materials plays an important role in their nanostructures and crystallinity, we speculate that the borates could help modulate the carbon growth environment’s oxo-acidity by regulating adjacent oxygen content and facilitating an ordered arrangement of carbon atoms in the basal planes, which needs systematic investigation in the future. It should be pointed out that the contrast between onset potential and theoretical potential for borate-involved CO 2 RR was only tens mV, implying that the overpotential to initiate CO 2 RR should be low.…”

Section: Cathodic Thermodynamics and Electrochemical Characterizationmentioning

confidence: 73%

Selective CO₂ Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Yang

Deng

et al. 2023

ACS Energy Lett.

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The renewable-electricity-driven carbon dioxide reduction reaction (CO2RR) is potentially a pathway to closing the anthropogenic carbon cycle; however, it is challenging to couple a fast cathodic CO2RR that endows tunable selectivity with a kinetically matched anodic oxygen evolution reaction (OER) at a promising energy efficiency. Here, we report a cost-effective strategy to convert CO2 into C/CO (tunable selectivity of over 70%) with enhanced OER kinetics in water-soluble Na-K-based molten carbonate by modulating the electrolyte’s oxo-acidity using earth-abundant borax (Na2B4O7) as an electrolyte additive, where the borates acting as O2– (an oxo-base) shuttles that constantly mediate between cathode and anode can concurrently facilitate CO2RR and OER. In particular, it can respectively sustain CO2RR at a stable current density of 100 mA cm–2 with a considerable OER current density of ∼300 mA cm–2. The optimal energy efficiency can reach up to over 60%, opening avenues for efficiently manipulating CO2RR and simultaneously enhancing OER.

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Section: Cathodic Thermodynamics and Electrochemical Characterizationmentioning

confidence: 73%

Selective CO₂ Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Yang

Deng

et al. 2023

ACS Energy Lett.

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“…It can be noticed from Figure that all the samples, apart from NB2 (has a small peak), have significant peaks between 50 and 100 °C, which is related to the pre-adsorbed moisture . Another weight loss shown above 200 and 400 °C could be assigned to the release of crystalline water over multiple steps . NB1, NB3, and NB4 adsorbent materials presented another weight loss accompanied with an endothermic peak above 600 °C, which is related to the melting point of NB3 (664 °C) and NB4 (614 °C), which agrees with the sodium boron phase diagram (S-1) that presents the melting point above 600 °C.…”

Section: Resultsmentioning

confidence: 93%

Development of Sodium-Based Borate Adsorbents for CO₂ Capture at High Temperatures

Al-Mamoori

Hameed

Saoud

et al. 2023

Ind. Eng. Chem. Res.

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The excessive amounts of CO 2 emissions to the atmosphere are a critical issue due to the global warming phenomenon. Development of CO 2 adsorbents at high temperatures is of paramount importance because of their widespread application. In this investigation, sodium-based borate adsorbents have been developed for the CO 2 capture process. Four different sodium precursors (NaOH, NaCl, Na 2 CO 3 , and NaNO 3 ) have been employed as a sodium source, their effects on a boric acid material was investigated, and they were tested for CO 2 capture application under different temperatures (500−700 °C). The proposed adsorbent materials showed promising results in terms of CO 2 capture efficacy. The maximum CO 2 uptake (5.45 mmol/g) and the fastest kinetic (90% of its capture uptake achieved within the first minute) have been obtained from the proposed NB4 (NaNO 3 @H 3 BO 3 ) material at 600 °C and 1 bar. However, NB2 (NaCl@H 3 BO 3 ) and the pristine materials (boric acid) showed no capacity toward CO 2 . Time on stream has also been tested for NB1, NB3, and NB4 after multiple cyclic adsorption−desorption. The materials showed high stability after eight consecutive adsorption−desorption cycles. For further investigation, XRD, FTIR, SEM, and TGA-DSC techniques have been performed for the proposed materials to study their crystalline composition structures, bonding interactions, material degradation, and melting points. The excellent performance of the newly synthesized materials is attributed to the chemical reaction of sodium borate with CO 2 with the aid of the molten phase that facilitates CO 2 diffusion over the proposed materials. The newly proposed materials could open a new avenue for CO 2 capture technology.

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“…However, it has been recently demonstrated that molten salt can function as an ideal electrolyte to capture, activate and convert CO 2 into advanced carbon and hydrocarbon [4–8] . This is due to a thermodynamically spontaneous reaction between CO 2 and O 2− in molten salts (Figure S1, Supporting Information), which thereby increases the solubility of CO 2 in molten salts to several moles per liter [9–12] . Molten salts also have larger electrochemical windows than that of aqueous solutions, making them less vulnerable to electrolyte decomposition.…”

Section: Figurementioning

confidence: 99%

“…[4][5][6][7][8] This is due to a thermodynamically spontaneous reaction between CO 2 and O 2À in molten salts (Figure S1, Supporting Information), which thereby increases the solubility of CO 2 in molten salts to several moles per liter. [9][10][11][12] Molten salts also have larger electrochemical…”

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confidence: 99%

Overall Carbon‐neutral Electrochemical Reduction of CO₂ in Molten Salts using a Liquid Metal Sn Cathode

et al. 2022

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An overall carbon‐neutral CO2 electroreduction requires enhanced conversion efficiency and intensified functionality of CO2‐derived products to balance the carbon footprint from CO2 electroreduction against fixed CO2. A liquid Sn cathode is herein introduced into electrochemical reduction of CO2 in molten salts to fabricate core–shell Sn−C spheres (Sn@C). An in situ generated Li2SnO3/C directs a self‐template formation of Sn@C. Benefitting from the accelerated reaction kinetics from the liquid Sn cathode and the core–shell structure of Sn@C, a CO2‐fixation current efficiency higher than 84 % and a high reversible lithium‐storage capacity of Sn@C are achieved. The versatility of this strategy is demonstrated by other low melting point metals, such as Zn and Bi. This process integrates energy‐efficient CO2 conversion and template‐free fabrication of value‐added metal‐carbon, achieving an overall carbon‐neutral electrochemical reduction of CO2.

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Capture and electrochemical conversion of CO₂ in molten alkali metal borate–carbonate blends

Abstract: A family of blended compositions of molten mixed lithium and sodium borate (Li1.5Na1.5BO3) and eutectic lithium-potassium carbonate (Li1.24K0.76CO3) salts has been introduced as reversible carbon dioxide absorbents and as media...

Cited by 15 publications

References 72 publications

Selective CO₂ Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Selective CO₂ Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Development of Sodium-Based Borate Adsorbents for CO₂ Capture at High Temperatures

Overall Carbon‐neutral Electrochemical Reduction of CO₂ in Molten Salts using a Liquid Metal Sn Cathode

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Capture and electrochemical conversion of CO2 in molten alkali metal borate–carbonate blends

Abstract: A family of blended compositions of molten mixed lithium and sodium borate (Li1.5Na1.5BO3) and eutectic lithium-potassium carbonate (Li1.24K0.76CO3) salts has been introduced as reversible carbon dioxide absorbents and as media...

Cited by 15 publications

References 72 publications

Selective CO2 Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Selective CO2 Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Development of Sodium-Based Borate Adsorbents for CO2 Capture at High Temperatures

Overall Carbon‐neutral Electrochemical Reduction of CO2 in Molten Salts using a Liquid Metal Sn Cathode

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Product

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Capture and electrochemical conversion of CO₂ in molten alkali metal borate–carbonate blends

Selective CO₂ Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Selective CO₂ Electroreduction with Enhanced Oxygen Evolution Efficiency in Affordable Borate-Mediated Molten Electrolyte

Development of Sodium-Based Borate Adsorbents for CO₂ Capture at High Temperatures

Overall Carbon‐neutral Electrochemical Reduction of CO₂ in Molten Salts using a Liquid Metal Sn Cathode