Production of ammonia as potential hydrogen carrier: Review on thermochemical and electrochemical processes

Ion exchange membrane (IEM) performance in electrochemical processes such as fuel cells, redox flow batteries, or reverse electrodialysis (RED) is typically quantified through membrane selectivity and conductivity, which together determine the energy efficiency. However, water and co-ion transport (i.e., osmosis and salt diffusion / fuel crossover) also impact energy efficiency by allowing uncontrolled mixing of the electrolyte solutions to occur. For example, in RED with hypersaline water sources, uncontrolled mixing consumes 20-50% of the available mixing energy. Thus, in addition to high selectivity and high conductivity, it is desirable for IEMs to have low permeability to water and salt in order to minimize energy losses. Unfortunately, there is very little quantitative water and salt permeability information available for commercial IEMs, making it difficult to select the best membrane for a particular application. Accordingly, we measured the water and salt transport properties of 20 commercial IEMs and analyzed the relationships between permeability, diffusion and partitioning according to the solution-diffusion model. We found that water and salt permeance vary over several orders of magnitude among commercial IEMs, making some membranes better-suited than others to electrochemical processes that involve high salt concentrations and/or concentration gradients. Water and salt diffusion coefficients were found to be the principal factors contributing to the differences in permeance among commercial IEMs. We also observed that water and salt permeability were highly correlated to one another for all IEMs studied, regardless of polymer type or reinforcement. This finding suggests that transport of mobile salt in IEMs is governed by the microstructure of the membrane, and provides clear evidence that mobile salt does not interact strongly with polymer chains in highly-swollen IEMs. <br>

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Oxidation of hydrogen peroxide at the dropping mercury electrode

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19842320 ◽

1984 ◽

Vol 49 (10) ◽

pp. 2320-2331 ◽

Cited By ~ 4

Author(s):

Miroslav Březina ◽

Martin Wedell

Keyword(s):

Hydrogen Peroxide ◽

Superoxide Anion ◽

Ph Value ◽

Mercury Electrode ◽

Electrode Process ◽

Electrochemical Processes ◽

Dropping Mercury Electrode ◽

Oxidation Of Hydrogen ◽

Decreasing Ph ◽

Rate Controlling Step

Reduction of oxygen and oxidation of hydrogen peroxide at the dropping mercury electrode are electrochemical processes strongly influenced both by the pH value and the anions in solution. With decreasing pH, both processes become irreversible, especially in the presence of anions with a negative φ2 potential of the diffusion part of the double layer. In the case of irreversible oxygen reduction, the concept that the rate-controlling step of the electrode process is the acceptance of the first electron with the formation of the superoxide anion, O2-, was substantiated. Oxidation of hydrogen peroxide becomes irreversible at a lower pH value than the reduction of oxygen. The slowest, i.e. rate-controlling step of the electrode process in borate buffers at pH 9-10 is the transfer of the second electron, i.e. oxidation of superoxide to oxygen.

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Influence of Multivector Field on Paste Preparation and Formation of Negative Electrodes of Lead Batteries

Batteries ◽

10.3390/batteries7020024 ◽

2021 ◽

Vol 7 (2) ◽

pp. 24

Author(s):

Boris Shirov ◽

Vesselin Naidenov ◽

Urii Markov

Keyword(s):

Active Material ◽

Negative Electrode ◽

Limiting Factors ◽

Skeletal Structure ◽

Experimental Result ◽

External Application ◽

Electrochemical Processes ◽

Depth Of Discharge ◽

Negative Electrodes ◽

Positive Effect

During the operation of the negative electrode, some critical processes take place, which are limiting factors for the operation of lead–acid batteries. To improve the efficiency of the negative active material and minimize these processes, external application of multivector field is proposed. Two applications of the multivector field are studied: during negative paste preparation and during formation. It is established that, when applying multivector field during negative paste preparation, the chemical processes proceed more efficiently. The results are better phase composition and crystallinity of the cured paste, thus increasing the capacity of the consequently built lead batteries by 12% on average. The application of a multivector field during the formation of negative active materials in lead batteries has a positive effect on the skeletal structure, the size and shape of the Pb crystals. This ensures longer service life, which is confirmed by the 17.5% Depth of Discharge continuous tests on 12 V/75 Ah batteries. The batteries formed under the influence of external multivector field showed 20% longer cycle life. Based on the experimental result, a most probable mechanism of the influence of the multivector field on the chemical and electrochemical processes in lead batteries during negative paste preparation and formation of negative active masses is proposed.

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