Hydrogen energy is a clean source of energy. Unlike non-renewable oil and coal, it produces water when it is burned, which is an environmentally friendly substance. Therefore, hydrogen energy has received a lot of attention. So far, photocatalytic technology can convert solar energy into hydrogen energy, which is an environmentally friendly and ideal way to prepare hydrogen. The currently employed photogenerated hydrogen systems mainly consist of two components: catalyst and electron donor. However, in most photocatalytic systems, the catalysts are made of inorganic semiconductor materials, thus limiting their photoresponse range. Therefore, it is more practical to explore coordination complex catalysts. Transition metal complex such as ruthenium, cobalt, and copper have unfilled orbitals that serve as centers for photogenerated electron and hole separation, which facilitate visible light absorption by photocatalysts. The construction of these transition metal complexes, which can absorb visible light efficiently, is beneficial to improve the light quantum yield.
The systems of photocatalytic hydrogen production
The early photocatalytic hydrogen production systems are generally composite catalytic systems containing four functional components. As shown in Figure 1, S is a photosensitizer capable of absorbing light energy; R is an electron relay; also known as an oxygen quencher; C is a catalyst (usually refers to coordination complexes); In addition, EDTA (ethylenediaminetetraacetic acid) as electron donors, also known as sacrificial agents. With the deepening of research, the photocatalytic hydrogen production system has gradually become simpler. The Sakai group  used heteronuclear complex RuPt for photocatalytic hydrogen production, which avoided the influence of multiple interfaces in the process of electron transfer. Therefore, the design idea of hydrogen production in one-component system provides a reference for people to study the photocatalytic system. Thus, people began to use the three-component reaction system composed of photosensitizer, catalyst (usually refers to coordination complexes), and sacrificial agent.
Figure 1. Composition of photocatalytic hydrogen production systems
In 2006, Eisenberg's group  pioneered the photocatalytic hydrogen production by using Pt (II) terpyridyl acetylide instead of Ru(bpy)32+, which was the first case of Pt (II) complexes as photosensitizers applied to photocatalytic hydrogen production, and since then, the era of Pt (II) complexes for hydrogen production was opened.
Figure 2. Photocatalytic hydrogen production system of Pt (II) terpyridyl acetylide complexes
Nowadays, more and more transition metal complexes are used for photocatalytic hydrogen production, including ruthenium, cobalt, copper, iron, nickel, etc. The following table gives the detailed parameters of the photocatalytic hydrogen production by several complexes.
Table 1. Detailed parameters of the photocatalytic hydrogen production by complexes
|Transition metal complex||Reaction solution||Photocatalytic Hydrogen Production/(μmol*s-1)||Light source|
|NaAscO/AscOH/H2O||22.5||100 mW LED|
|EDTA/H2O||6.90||400 W Hg lamp|
|TEOA/CH3CN/H2O||4.96||500W Xe lamp|
|TEOA/CH3CN/H2O||43.0||500 mW LED|
What can we do?
The coordination complexes produced by Alfa Chemistry have a promising future in the field of photocatalytic hydrogen production. With the help of photocatalytic technology, the catalytic reduction of water in nature to hydrogen and oxygen can be carried out using a coordination complex catalyst. Thus, the environmental problems can be alleviated to a certain extent. Alfa Chemistry provides you with the most professional services and the most favorable prices. If you have any problems, we will provide technical support for you. If you have special needs, we will develop a unique solution for you. Please don't hesitate to contact us.
- Ozawa, H.; et al. A photo-hydrogen-evolving molecular device driving visible-light-induced EDTA-reduction of water into molecular hydrogen. J. Am. Chem. Soc. 2006, 128: 4926-4927.
- Schneider, J.; et al. Photocatalytic generation of hydrogen from water using a platinum (II) terpyridyl acetylide chromophore. J. Am. Chem. Soc. 2006, 128: 7726-7727.