Let sunlight "produce" hydrogen: a new way to play Z-type photocatalytic system

The development of clean and renewable energy is an inevitable choice to alleviate the energy shortage and environmental degradation Hydrogen is considered as the most ideal clean fuel because its combustion products have no secondary pollution Solar photocatalytic decomposition of water for hydrogen production provides a promising technology path for clean and efficient conversion and utilization of solar energy and elimination of environmental pollution, which attracts the research interest of scholars at home and abroad The photocatalytic reaction should be carried out in accordance with the requirements of thermodynamics and kinetics It is required that the photocatalytic materials have a narrow energy gap, so as to absorb more light energy and generate photogenerated electrons and holes, and that the photocatalytic materials have a proper large energy gap, so as to have a suitable oxidation potential for catalytic reaction At present, TiO2, WO3 and other photocatalytic materials are widely studied, but the efficiency is very low: the single catalyst has the problem of low visible light utilization or high electron hole recombination rate, which seriously restricts its photocatalytic hydrogen production performance Cd0.8zn0.2s/au/g-c3n4 photocatalytic hydrogen production process (source: Science Bulletin) [introduction] in view of this, researchers of the environmental science and Technology Research Office of Xinjiang Institute of physical and chemical technology, Chinese Academy of Sciences found that it mainly consists of two photosystems and one photosynthetic chain through careful study of plant photosynthesis Water oxidation occurs after photosystem II (PS II) absorbs light, and the electrons generated by it are transmitted to photosystem I (PS I) through a transport channel - "photosynthetic chain" After absorbing the light energy, PS I generates electrons, which form a strong reducing coenzyme II (NADP) to reduce CO2 and generate sugars, while it is reduced by electrons transmitted from PS II The electron transfer chain is Z-shaped, so it is called Z-type reaction The quantum efficiency of this reaction is close to 100% The artificial Z-type photocatalysis system is composed of oxidation catalyst (PSII), reduction catalyst (PSII) and electronic mediator Under the irradiation of light, the two kinds of catalysts in the Z-type photocatalysis system produce photogenerated charge, the photogenerated electrons of PS II migrate to the electron mediator, and then compound with the photogenerated holes of PS II, while the photogenerated electrons in PS I take place reduction reaction, and the photogenerated holes in PS II take place oxidation reaction The Z-type photocatalysis system has outstanding advantages: (1) reduction reaction and oxidation reaction are respectively completed on different photocatalysts by means of two-photon excitation process; (2) the photocatalysts in the Z-type photocatalysis system only need to meet their own photoexcitation process and corresponding half reaction, which reduces the thermodynamic requirements of photocatalysis reaction and provides a great deal for the selection and design of photocatalysis materials Space; (3) the process of oxidation and reduction are separated from each other, which can effectively inhibit the occurrence of the reverse reaction; (4) using electronic medium, the photogenerated electrons and holes in the Z-type photocatalytic system can be effectively separated and transmitted, maintaining strong oxidation-reduction ability; (5) the photogenerated holes of hydrogen catalyst and oxygen catalyst are combined, which enhances the stability of the photocatalytic system After a series of research precipitation, the research team recently grew Au nanoparticles on the g-c3n4 substrate by photodeposition method, and then loaded cdxzn1 − XS solid solution on Au to prepare Z-type cdxzn1 − XS / Au / g-c3n4 photocatalyst, and systematically studied its structure, morphology and optical properties Using glucose as a sacrificial agent, the photocatalytic activity of Z-type photocatalyst for the preparation of hydrogen from water under visible light (λ > 420nm) was studied The results show that cd0.8zn0.2s/au/g-c3n4 has excellent hydrogen production performance, which are 52.2 times and 8.63 times of Au / g-c3n4 and CDs / Au / g-c3n4, respectively; the improvement of hydrogen production activity of Z-type photocatalyst is mainly due to the efficient separation of photocarriers In addition, the introduction of cd0.8zn0.2s can inhibit the production of CO and CO2 in the photocatalytic process [application] the catalytic material has unique electronic structure, stable chemical properties and significant visible light catalytic activity The catalytic system has high catalytic efficiency and low electron hole recombination rate, which provides a new idea for the design of high-efficiency photocatalytic hydrogen production catalyst, and shows great application potential in the field of photocatalysis Therefore, the research results are published in science bulletin as "front cover" Paper link: http://www.sciencedirect.com/science/article/pii/s2095927317301287