Biological hydrogen production can be divided into three types: hydrogen production by photolysis of water, hydrogen production by anaerobic bacteria and hydrogen production by photosynthetic bacteria. According to different microorganisms, hydrogen-producing substances and hydrogen-producing mechanisms, biological hydrogen production can be divided into three types: photolysis of aquatic hydrogen, anaerobic hydrogen production and photosynthetic hydrogen production. See table 1 for its characteristics. Green algae takes water as raw material, and the process of hydrogen production needs illumination with high solar energy conversion rate, which has a great influence on the hydrogen production of the system, and the generated oxygen will inhibit the reaction. Cyanobacteria use water as raw material, and hydrogen production is mainly completed by nitrogenase, which can fix N2 in the atmosphere. The process of hydrogen production needs illumination, and the generated oxygen can inhibit nitrogenase. Anaerobic bacteria can continuously produce hydrogen without light, and can use various organic substances as substrates. The process of hydrogen production is anaerobic, and there is no oxygen limitation. The system is easy to realize the amplification test reaction, and the pH value needs to be controlled in the acidic range, so the utilization rate of raw materials is low. The inhibitory effect of the product is obvious. Photosynthetic bacteria have high hydrogen production efficiency, can use a variety of organic wastes as raw materials, and have a wide spectral range. Without the inhibition of oxygen, the hydrogen production process needs illumination, so it is not easy to carry out scale-up test (1). Hydrogen production by photolysis is that photosynthetic organisms decompose water through photosynthesis under anaerobic conditions to generate organic matter and release hydrogen at the same time. Its mechanism of action is similar to that of green plants. In some algae and eukaryotes (cyanobacteria), there are two photosynthetic centers, such as PS ⅰ and PS ⅱ. PS Ⅰ generates reductant to fix CO2, and PS Ⅱ receives solar energy to decompose water to generate H+, electrons and O2. Electrons generated by PS ⅱ are carried by iron redox proteins, and reach hydrogenase through PS ⅱ and PS ⅰ, and H+ forms H2 under the catalysis of hydrogenase. Among them, the system of photolysis of aquatic hydrogen by algae is called direct photolysis hydrogen production system, and the system of photolysis hydrogen production by cyanobacteria is called indirect photolysis hydrogen production system. Hydrogen production by algae is catalyzed by hydrogenase, and water can be used as the original donor of electrons and protons, which is the main advantage of hydrogen production by algae. Cyanobacteria have both nitrogenase and hydrogenase, and their hydrogen production process is mainly influenced by nitrogenase, and hydrogenase mainly acts on the direction of hydrogen absorption. Cyanobacteria can also use water as the final electron donor, and the electrons and protons needed for hydrogen production also come from the cracking of water: hydrogen production process by anaerobic bacteria: glucose? c6h 12o 6+2H2O→2ch 3 cooh+2co 2+4h 2？ △G =- 184 kJ c6h 12o 6→CH3(CH2)2c ooh+2 CO2+2 H2？ △G= -257 kJ Hydrogen production process of photosynthetic bacteria: glucose C6H 12O6+2H2O→6CO2+8H2? △G = -34 kJ Acetic acid CH3COOH+2H2O→2CO2+4H2? △G = 75 kJ The process of hydrogen production by photolysis of aquatic products: 4H2O ++ light energy → 2o2+4h2? △G = 1498 kJ Although it can be seen from the variation law of Gibbs free energy of hydrogen production reaction that anaerobic bacteria are very beneficial to hydrogen production by fermentation, and can obtain more free energy from hydrogen production reaction than photosynthetic bacteria, the rate of decomposition of organic matter by anaerobic bacteria is slow and incomplete, which significantly reduces the hydrogen production rate and output. Theoretically, 1mol glucose can only produce 2 ~ 4 mol hydrogen. In terms of Gibbs free energy change of hydrogen production reaction, photolytic algae can produce hydrogen roughly similar to anaerobic fermentation, and can obtain more free energy from hydrogen production reaction than photosynthetic bacteria. However, the hydrogen production system of algae is very unstable due to the inhibition of hydrogenase and oxygen in principle, which is not conducive to effectively improving the hydrogen production rate and quantity in the process of photolysis. In the hydrogen production reaction of photosynthetic bacteria, it can be seen from the change law of Gibbs free energy of hydrogen production reaction that although only a small amount of free energy can be obtained, even a large amount of free energy has to be paid, photosynthetic bacteria can obtain enough ATP through photosynthetic phosphorylation to make the reaction proceed effectively. Theoretically, photosynthetic bacteria can convert 1mol glucose into 12mol hydrogen [2 1]. Obviously, the key to the development of hydrogen production technology by photosynthetic bacteria is illumination technology. Choosing suitable light source and reducing illumination energy consumption have become two key technologies to solve the hydrogen production technology by photosynthetic bacteria. The technology of hydrogen production by photosynthetic bacteria using solar energy as light source can fundamentally solve the problems of lighting energy consumption and hydrogen production cost, and has strong technical feasibility and potential development prospects, which has attracted much attention in the energy field. Research progress of hydrogen production technology by photosynthetic organisms In recent years, experimental research on hydrogen production by photosynthetic organisms has been carried out at home and abroad to improve the light conversion efficiency of photosynthetic bacteria, among which the research progress of the Key Open Laboratory of Renewable Energy and Agriculture Department of Henan Agricultural University is the most representative. With the support of the National Natural Science Foundation, the National 863 Program, the Doctoral Program Fund of the Ministry of Education and international cooperation, the key theoretical and technical issues such as screening and cultivation of high-efficiency photosynthetic hydrogen-producing bacteria with fecal sewage as raw materials, hydrogen-producing process conditions, immobilization methods, solar automatic tracking lighting and optical fiber light guiding system, and spectral coupling characteristics of solar photosynthetic hydrogen-producing bacteria have been systematically and deeply studied, and some important progress has been made [22 ~ 27]. (1) has made great progress in breeding photosynthetic hydrogen-producing strains from livestock manure. Twenty-four typical samples were obtained from six representative locations. According to the growth conditions and nutritional requirements of various photosynthetic bacteria, the corresponding culture medium and culture conditions were designed from the aspects of medium composition, pH value, illumination time and period, culture temperature and anaerobic state. Thirty-three strains of photosynthetic bacteria were widely enriched and isolated. According to the composition characteristics of pig manure, the pig manure, related small molecular organic acids and hydrogen production capacity were studied, and 7 strains were screened out. (2) A solar energy efficient focusing and collecting system with automatic sun tracking and adjustable filter is successfully developed, and the optical transmission and spectral coupling performance of the system are optimized. In order to improve the utilization rate of solar energy, a Fresnel lens concentrating solar light guiding lighting system was developed. Fresnel lens focusing method is used to focus sunlight on the focal point, and optical fiber is placed on the focal point. After being selectively filtered by the adjustable filter, it is input into the photosynthetic bioreactor through optical fiber to realize the efficient transmission of sunlight. At the same time, the solar absorption spectra of seven screened photosynthetic bacteria were studied, and the correlation between the growth characteristics of photosynthetic bacteria in different bands and the hydrogen production characteristics using pig manure sewage as substrate was put forward. The coupling performance of light transmission and spectrum in the process of hydrogen production by sunlight photosynthetic organisms was explored, and the ways to further improve the efficiency of hydrogen production by sunlight photosynthetic organisms were also explored. (3) A novel circulating cell reactor with high surface area and high volume ratio was successfully developed, and the attenuation characteristics of light in the reactor were systematically studied. According to the growth and metabolic characteristics of photosynthetic hydrogen-producing bacteria, the developed circulating tank-type photosynthetic biological hydrogen-producing reactor has the characteristics of weakening the mutual shielding effect between photosynthetic bacteria cells and livestock manure sewage by using the ratio of high light surface area to volume, generating a "flicker effect" around the bacteria by controlling the circulating flow of the reaction liquid, effectively improving the propagation path and quality of light, and automatically controlling the reaction conditions of photosynthetic hydrogen production. Photosynthetic bacteria are in the best growth and metabolism conditions. By optimizing the control of temperature, illumination, pH value, substrate concentration, different inoculation amount and dissolved oxygen level, the light conversion efficiency and hydrogen production can be optimized. (4) The thermodynamic characteristics of hydrogen production by solar photosynthetic organisms were systematically studied, and the influence of thermodynamic characteristics on hydrogen production enzyme activity and hydrogen production rate of photosynthetic bacteria was revealed. The law of heat production in the process of growth and metabolism of hydrogen-producing bacteria by photosynthetic organisms was analyzed by thermodynamic method, and the thermodynamic information of growth and metabolism of hydrogen-producing bacteria by solar photosynthetic organisms was obtained, and the temperature field distribution of hydrogen-producing system by photosynthetic organisms was studied. A model to characterize the thermodynamic characteristics of hydrogen production by solar photosynthetic organisms was established, and the optimum growth and metabolic temperature and energy flow process conditions of photosynthetic hydrogen-producing bacteria were optimized, which provided scientific reference and theoretical basis for further design and large-scale production and operation experiments of photosynthetic bioreactors. Tel: 86-20-2336 1 169 This article comes from: Guangzhou Linglong Electronic Technology Co., Ltd. Hydrogen Production and Hydrogen Fuel Cell (www.liongon.com).