Biomimetic hydrogen production from formic acid with platinum nano-particle

摘要

In recent years, clean energy without producing CO_2 such as hydrogen, instead of fossil fuels has attracted attention. To exploit hydrogen for energy resourse, it is required to store hydrogen in the substance (hydrogen carrier), and to convert to hydrogen gas from carrier molecule. Formic acid is candidate for hydrogen carrier molecule. Formic acid contains 53 g LD1 hydrogen at room temperature and atmospheric pressure. By weight, pure formic acid stores 4.3 wt% hydrogen. Pure formic acid is a liquid with a flash point 69 °C (cf. gasoline □ 40 °C, ethanol 13 °C). 85% formic acid is not flammable. On the other hand, CO_2 conversion to organic molecule with visible light irradiation is potential technology for the realization of catalytic CO_2 reduction. Some studies on the visible-light induced CO_2 conversion to organic molecules with enzyme and photo-redox system have been reported [1,2]. For example, formic acid production from CO2 with the system of methylviologen (MV~(2+)) photoreduction using a system containing ruthenium(II) coordination compound as a photosensitiser and mercaptoethanol (RSH) as an electron donor in the presence of formate dehydrogenase (FDH) also has been reported [3]. We also previously reported the visible-light induced enzymatic formic acid production from HCO_3 or CO_2 with FDH using the photosensitization of water-soluble zinc poirphyrin or chlorophyll-a[4-6]. Our strategy is the development of hydrogen storage and production cycle via formic acid with catalytic and artificial photosynthesis based on the photo-redox system as shown in Figure 1. Thus, highly active catalyst is required for carrier to hydrogen conversion.