| 1. |
- Wang, Huan, et al.
(författare)
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MnO2/Mn2+ chemistry: Charging protocol and electrolyte regulation
- 2023
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Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8289 .- 2405-8297. ; 63
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous rechargeable Zn-MnO2 batteries based on the dissolution/deposition mechanism of MnO2/Mn2+are gaining increasing attention due to their high capacity and structural simplicity. One of the major concerns is the Mn2+/Mn3+side reaction, which hampers the coulombic efficiency (CE) due to Mn3+(aq) disproportionation. However, factors affecting Mn3+ formation have not been systematically investigated. In this study, we utilized in situ optical microscopy and Scanning Electron Microscopy (SEM) to evaluate the formation of Mn3+ by observing its disproportionation product: the randomly deposited MnO2. We found that an excessively high charging voltage and a low electrolyte pH (pH<4.2) were shown to adversely accelerate Mn3+ formation. Most reports on the Mn2+/MnO2 cathode indicate a coulombic efficiency of only 80 % on carbon felt (thickness: 2.5 mm) at 2 mAh/cm2 due to the inherently low electrical conductivity of MnO2. Here with the optimized charging protocol and the utilization of the anode-friendly, methanesulfonic acid (MSA)-containing electrolyte, we achieved a CE of nearly 100 % for up to 200 cycles at 2 mAh/cm2. This work gives guidelines on the electrolyte design and charging protocol optimization towards high-performance MnO2/Mn2+cathodes.
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| 2. |
- Wang, Tongshuai, et al.
(författare)
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Pilot-scale study of membrane-coated cathodes : Achieving high cathodic efficiency and outstanding stability in chlorate electrolysis
- 2024
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 497
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Tidskriftsartikel (refereegranskat)abstract
- Sodium chlorate (NaClO3) is primarily used for producing chlorine dioxide, an environmentally friendly bleaching agent for pulp. Currently, dichromate is used as an electrolyte additive in the chlorate process where it has several functions, but due to health and environmental risks associated with chromate, there is a need for a less toxic alternative. In the present study, we prepared a membrane-coated cathode as a substitute for chromium(VI), to keep a high current efficiency in chlorate electrolysis. This electrode employed an industrially relevant electrode with active catalysts as the substrate and a thin layer of ion exchange polymer as the coating. The coating effectively blocked anions such as ClO− and ClO3− from reaching the cathode, thereby suppressing cathodic side reactions. We conducted a series of electrochemical characterizations on the membrane-coated cathodes with varying coating thickness and tested them in a pilot-scale setup for efficiency and stability under industrial testing conditions.
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| 3. |
- Wang, Tongshuai, et al.
(författare)
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Rational design of a membrane-coated cathode for selective electrochemical hydrogen evolution in chlorate electrolysis
- 2023
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 466, s. 143010-
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Tidskriftsartikel (refereegranskat)abstract
- The industrial chlorate process has traditionally used chromium(VI) as an electrolyte additive for high Faraday efficiency. However, due to its recognized toxicity and carcinogenic properties, the EU has regulated its usage, prompting the need for alternative approaches. In this study, we propose the adoption of a polymeric membrane-coated cathode (MCC) as a straightforward yet highly efficient solution to enhance the selectivity of the hydrogen evolution reaction (HER) in chlorate electrolysis. Proof-of-concept MCCs were fabricated by coating roughened titanium substrates with cation and anion exchange membrane layers, which function as selective barriers for anodic hypochlorite species. The study revealed that a thin membrane coating on the electrode surface effectively suppressed the permeation of anodic intermediates, without compromising the current density for HER. By optimizing the coating layer thickness and substrate surface properties of MCC, the chlorate electrolysis cell demonstrated an impressive Faradaic efficiency of up to 95% at a current density of 150 mA/cm², while maintaining exceptional stability. The outcome of this study can potentially advance the feasibility of industrial chlorate production in meeting regulatory requirements and effectively mitigating environmental consequences.
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