Principles of production and practical operations.
1. Production principle: hydrogen-oxygen fuel cells generate electrical energy through the reaction of hydrogen and oxygen, while the electrolysis of water to produce hydrogen produces hydrogen and oxygen by the decomposition of water with electrical energy. These two processes are actually reversible and a hydrogen-oxygen fuel cell can be converted into electrolyzed water to produce hydrogen.
2. Convenient operation: Electrolysis of water to produce hydrogen requires a large amount of electricity, and the efficiency of hydrogen production is low, so the cost is high. Hydrogen-oxygen fuel cells can directly convert chemical energy into electrical energy with high energy conversion efficiency.
Under normal circumstances, why can't water be directlynt transformed into hydrogen and oxygen as fuel?
Electrolysis of water to produce one kilogram of hydrogen requires 56 kilowatt hours of electricity. Electrolysis of water to produce a standard cubic meter of hydrogen requires about 5 kilowatt hours of electricity. The calorific value of 1 kilogram of hydrogen is equivalent to approximately 33 kW/h (kWh) of electricity. The power generation efficiency of hydrogen fuel cells typically operates between 40% and 60%. Typically calculated based on 50% efficiency, 1 kilogram of hydrogen can produce electricity at around 16 degrees Celsius. 11.2 The standard cubic meter of hydrogen is equivalent to 1 kg. Therefore, the power consumption of water electrolysis to produce 1 kilogram of hydrogen is approximately 56 kilowatt hours.
Principle of hydrogen production by electrolysis of water:
When a direct current passese in some electrolytic aqueous solutions, the decomposed substances have nothing to do with the What decomposes is water as the solvent, and the original electrolyte remains in the water. For example, sulfuric acid, sodium hydroxide, potassium hydroxide, etc. all belong to this type of electrolytes. ?During water electrolysis, because the ionization degree of pure water is very low and its conductivity is low, it is a typical weak electrolyte. Therefore, it is necessary to add the aforementioned electrolyte to increase the conductivity of the solution so that water can. Be electrolyzed into hydrogen and oxygen smoothly.
Reference for the above content: Baidu Encyclopedia-Hydrogen production by water electrolysis
At present, in addition of the technology for producing hydrogen by photolysis of water launched in 1972, developed by the University of Tokyo, Japan,Professors Fujishima A and Honda K first reported the phenomenon of a single-crystal TiO2 electrode photocatalytically decomposing water to produce hydrogen. Until now, no very good catalyst has been found that can quickly decompose water into hydrogen and oxygen.
Water cannot replace gasoline as a fuel; water is not flammable and cannot be used as fuel. Hydrogen is produced by the decomposition of water under certain conditions and can be used as fuel. It is impossible for water to transform into gasoline because the two components are different; otherwise it would violate the law of conservation of mass.
Hydrogen and oxygen have higher energy than water, so combining the two in water releases energy, while breaking down water into hydrogen and Oxygen requires energy. Hydrogen and oxygen in water are in a verystable (very low energy). If water can produce a substance with less energy through chemical changes, water can be used as fuel to release energy. However, the current earth environment and the accumulation of human chemical knowledge over hundreds of years have not yet discovered this substance, so water cannot yet be used as fuel on earth .
The existence of hydrogen bonds affects the morphology and chemistry of tissues. Hydrogen bonds in water make water very stable, such as chemical reactivity, etc. Only at a high temperature of around 1300°C or with electricity can water be decomposed into oxygen and hydrogen (volume ratio 1:2 due to the cost of water). water electrolysis and water decomposition at high temperature are too high. Scientists are looking for a new type of catalyst that can turn water into hydrogen and oxygen at room temperature, but there are currently no reports on this.