High-efficiency Photocatalyst Utilizes All Sunlight in Infrared Region

A Japanese research group has synthesized a high-efficiency photocatalyst responsive to infrared light.

Its external quantum efficiency is 3.8% with a wavelength of 1,100nm. With the photocatalyst, the group succeeded in generating hydrogen by using light with a wavelength of 1,500nm, which is the maximum wavelength of sunlight that reaches the surface of the earth. This means that the photocatalyst can carry out energy conversion of almost all of sunlight in the infrared region with a high efficiency.

The group consists of researchers from Kyoto University, Toyota Technological Institute, Kwansei Gakuin University, Ritsumeikan University and National Institute for Materials Science (NIMS).

Photoelectric conversion using LSPR (localized surface plasmon resonance) is expected to be a key technology for high-efficiency energy conversion of infrared light because LSPR has properties that enable to control light having a wide wavelength range from ultraviolet to infrared regions. This time, the group synthesized heterostructure nanoparticles connecting cadmium sulfide nanoparticles and copper sulfide (Cu7S4) nanoparticles, which triggers LSPR with light in the infrared region. And the group evaluated its activity as a hydrogen-generating photocatalyst.

The group measured the catalytic activity in terms of hydrogen generation when the synthesized heterostructure nanoparticles are irradiated with infrared light by gaschromatography. As a result, it found that platinum-carrying copper sulfide/cadmium sulfide heterostructure nanoparticles is a photocatalyst capable of generating hydrogen from infrared light at an external quantum efficiency of 3.8% with a wavelength of 1,100nm. This is the highest efficiency of a photocatalyst responsive to infrared light that has been reported so far, the group said.

Furthermore, the group observed plasmon-induced charge isolation by time-resolved transient absorption spectroscopic measurement and found that thermal electrons produced by LSPR excitation move to the side of cadmium sulfide. Also, it showed a long charge separation life of about 273μs. It is much longer than that of commonly-used existing plasmon-induced charge isolation and considered to be greatly contributing to the high-efficiency energy conversion of infrared light.

The latest findings are expected to lead to the development of new light energy conversion materials using light in the infrared region (e.g. photocatalyst responsive to infrared light and material for photoelectric conversion using infrared light). The research results were published in the online edition of Journal of the American Chemical Society (international academic journal).

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