Molten electrolytes are highly efficient at high temperature operations

Molten electrolytes are highly efficient at high temperature operations

High-temperature fuel cells were originally conceived with molten salt electrolytes, which were later improved by the University of Amsterdam and the Netherlands Institute [10]. The electrolyte used is a solid electrolyte, but acts electrochemically as a liquid molten electrolyte. The surface of the electrode is usually composed of metal powder. This includes Ag for the air or oxygen cathode and Fe, Ni and a zinc oxide/silver mixture for the anode. These molten electrolytes, which are usually difficult to undergo electrochemical reactions, can easily generate high current densities exceeding 100 mA/cm² at 0.7 V at high temperatures (600 ~ 800 °C). Even at high temperatures, hydrogen exhibits only low polarization.

Hydrocarbons also generate electricity in these cells, but strictly speaking this is due to the formation of hydrogen or carbon dioxide during thermal decomposition. High temperature fuel cells offer the possibility to use cheap fuels such as coal, natural gas and oil to generate electricity with at least 2 times the conversion efficiency compared to the usual thermal methods, ranging from 65% to 75% compared to conventional thermal power plants30 %~40%. This means that high-temperature fuel cells are better suited for generating large amounts of electricity with much higher efficiency than thermal power plants.

Fuel cells provide a more efficient technology for converting thermal energy into electrical energy. Regardless of operating temperature, fuel cells offer the following advantages:
The thermal energy conversion efficiency ranges from 60% to 85%;
The weight and volume are reduced in the order of 1/10~1/100;
 Low-cost production of electricity;
 The most cost-effective source of portable power generation.

  1. Properties of Porous Electrodes
Application of Porous Carbon/Sulfur Composite Cathode Materials in Lithium-Sulfur Batteries
Application of Porous Carbon/Sulfur Composite Cathode Materials in Lithium-Sulfur Batteries

The most important fact recognized by designers of fuel cells: the application of porous electrodes significantly improves performance. The designers strongly believe that the use of porous electrodes maximizes the interfacial area of ​​the catalyst per unit geometric area of ​​the electrode, resulting in a significant increase in the output power of the device. In fuel cells, electrolysis and liquefaction of gases as catalysts are used to increase efficiency. Electrodes must be designed to maximize the available catalyst area, minimize resistance to electrolysis and mass transport in the gas phase and electron resistance in the solid phase. Obviously, this is a strict performance requirement. Porous electrode theory provides a three-dimensional structural composition with continuous transport paths in the composite phase, as well as a reliable mathematical framework to model complex electrode structures in terms of the well-defined macroscopic variables involved.

Materials scientists believe that the porous electrode theory has been used to describe a variety of electrochemical devices, including fuel cells, rechargeable batteries, separable devices, and electrochemical capacitors. In many of these devices, with the exception of fuel cells, the electrodes contain a single solid phase and a single fluid phase. For fuel cells, the electrode contains more than one fluid phase, which not only adds additional complexity but also reduces the cell’s conversion efficiency. Classical gas diffusion electrodes contain an electrolytic phase and a gas phase in addition to the solid, electronically conductive phase. In summary, porous electrodes tend to increase thermodynamic and electrochemical efficiencies, resulting in significant improvements in fuel cell performance.

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