Current situation and future development trend of hydrogen technology

Solid oxide water electrolyzer (SOEC) : The high temperature electrolysis method is based on high temperature fuel cell technology and is the reverse application of solid oxide fuel cell (SOFC). A typical technique is a solid oxide cell. The operating temperature of the solid electrolyte high temperature water vapor electrolyzer is about 1000℃, which is composed of a porous anode, cathode, solid electrolyte and connecting materials. The solid electrolyte is usually composed of yttrium-doped zirconia ceramics. When 1000℃ high temperature water vapor passes through the cathode plate, it is dissociated into hydrogen and oxygen ions, and oxygen ions pass through the cathode plate, and the solid electrolyte reaches the anode, where it loses electrons to generate oxygen.

At present, the hydrogen production technology of alkaline water electrolyzer (ALK) in China is mature and has a high market share, but there is still a certain gap with foreign countries in important technical indicators such as hydrogen production efficiency. Proton exchange membrane water electrolyzer (PEM) technology is just starting, performance, especially life is still lack of market verification, overall behind Europe and the United States.

In addition, it is worth mentioning that in recent years, the new mechanism of "liquid sunlight" energy conversion and utilization led by the team of academician Li Can of the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences has gradually moved from basic research to preliminary industrial scale production. "Liquid sunlight" uses electricity generated by renewable energy sources such as solar energy to electrolyze water to produce "green" hydrogen energy, and uses the resulting hydrogen to hydrogenate carbon dioxide to produce liquid fuels such as "green" methanol. At present, the world's first large-scale (kiloton) synthetic green methanol demonstration plant has been first tested in the Green Chemical Industry Park in Lanzhou New District, Gansu Province, providing a new way from renewable energy to green liquid fuel methanol production.

3. Biological hydrogen production

Biological hydrogen production method is based on biological active enzyme catalysis as the main mechanism to decompose organic matter and biomass hydrogen production, its main advantages are wide sources and no pollution, the reaction environment is normal temperature and pressure, low production costs, completely subvert the traditional energy production process. At present, the commonly used biological hydrogen production methods can be summarized into four kinds: photolytic water, light fermentation, dark fermentation and light-dark fermentation coupling hydrogen production.

There are some problems in the field of biological hydrogen production that limit its industrial development: (1) Although hydrogen production by dark fermentation is stable and fast, it is limited by feedback inhibition due to the accumulation of volatile acids. (2) The low efficiency of light energy conversion is the main limiting factor in the production of hydrogen from microbial photolysis water. By means of genetic engineering, it is of great significance to obtain hydrogen production strains with higher light energy conversion efficiency through modification or mutagenesis. (3) There were significant differences in growth rate and acid tolerance between the two types of bacteria in light-dark coupled fermentation for hydrogen production. The acid production rate of dark fermentation process is fast, which reduces the pH value of the system, thus inhibiting the growth of hydrogen production bacteria by light fermentation, and reducing the hydrogen efficiency of the whole system. How to remove the product inhibition between the two types of bacteria and achieve mutualism is an urgent problem to be solved.

4. Hydrogen production from industrial by-product gas

The development space of industrial by-product hydrogen production is large, which can improve the efficiency of resource utilization and economic benefits while reducing air pollution. At the same time, China produces a large amount of coke oven gas from coke, the annual output is basically stable between 30 million and 35 million tons of caustic soda synthesis gas, methanol and synthetic ammonia industry, propane dehydrogenation project synthesis gas for industrial by-product purification of hydrogen to provide a large number of raw materials, and purification costs are low.

The technical difficulty of obtaining fuel hydrogen is mainly purification, 99.999% of industrial high purity hydrogen is difficult to meet the requirements of fuel hydrogen for trace impurities. In terms of hydrogen purity, 99.99% of high-purity hydrogen can meet the requirements of 99.97% of fuel hydrogen, but the difficulty lies in the trace impurities in hydrogen, especially CO≦0.2ppm is 99.99% of industrial pure hydrogen or even 99.999% of industrial high-purity hydrogen is difficult to achieve. Industrial hydrogen focuses on hydrogen purity, while fuel hydrogen focuses on specific impurity content. CO is the most difficult to deal with impurities contained in hydrogen, trace CO will lead to the toxic inactivation of fuel cell catalyst Pt, in order to meet the requirements of CO≦0.2ppm, it is necessary to remove impurities such as N2 and Ar, which are not high in the content of fuel hydrogen, to a very low level, the result is the loss of yield resulting in an increase in the cost of fuel hydrogen.