Development of the nano devices with photo-hydrogen-evolving abilities

人们越来越认识到，石油、煤炭和天然气等化石燃料的储量有限，向可再生能源过渡是必要和紧迫的。鉴于全球气候变暖、空气污染等全球性和区域性环境问题，人们普遍认为氢将成为石油的重要补充，但基本的实际问题仍有待解决。尽管以H_2和1/2O_2为基础的燃料电池汽车的发展取得了迅速的技术进步，但产生和储存氢气的方法还没有很好地建立起来。在这种背景下，水的电化学分解为H_2和1/2O_2被认为是作为制氢方法的候选者之一，其中风力发电站或太阳能电池被认为是作为电力来源。然而，投资于这种系统的能量的能量回报仍然不符合实际使用的标准。另一方面， 关于我们 另一方面，还已知在用蒸汽处理甲烷时产生氢气，这也导致作为副产物的温室气体（CO_2）的排放。此外，这个过程需要能量来产生蒸汽。由于水和太阳光资源丰富，且无CO_2排放，因此，光催化体系促进水分解为H_2和1/2O_2的研究受到了广泛的关注。（2，2 ′-联吡啶）钌（II）、甲基紫精和析氢催化剂，其中特定的Pt（II）络合物用作催化剂。此外，还不断努力开发由光敏化钌（II）中心和铂（II）催化剂中心组成的光-析氢分子器件。本文报道了Ru（Ⅱ）Pt（Ⅱ）和Ru（Ⅱ）_2Pt（Ⅱ）_2的各种配合物的合成和性质。然而，我们一直无法证明这种分子装置的有效性。我们最近成功地制备了第一个Ru（II）Pt（II）基分子器件，该器件有效地催化了可见光诱导的EDTA还原水为分子氢。为了阐明影响Ru（II）Pt（II）基分子器件光催化活性的重要因素，我们制备了几种结构类似物，并对它们的光催化放氢活性进行了评价。实验结果表明，在Ar气氛下，在EDTA存在下，含肽连接的器件在氙灯照射下能放出H_2。另一方面，具有两个或多个光敏钌（II）中心的化合物对光化学H_2的产生是无效的，这可能是由于增强了分子内能量转移猝灭过程。少

There is an increasing understanding that the reserves of fossil fuels, such as oil, coal, and natural gas, are limited and the transition to renewable energies is necessary and urgent. In view of the global and regional environmental issues such as global warming and air pollution, it is generally considered that hydrogen would become an important supplement to oil, even though basic practical problems still need a solution. In spite of the rapid technological advance in the development of fuel-cell cars based on H_2 and 1/2O_2, the means of generating and storing hydrogen gas has not been well established as yet. In this context, the electrochemical decomposition of water into H_2 and 1/2O_2 is regarded as one of the candidates as a method of generating hydrogen, where wind power stations or solar batteries are considered as the source of electricity. Nevertheless, the energy return on energy invested in such systems still does not meet the criteria for the practical use. On the othe … More r hand, hydrogen is also known to be generated upon the treatment of methane with steam, which also leads to the emission of greenhouse gas (CO_2) as a byproduct. Moreover, this process requires the energy to produce the steam. Consequently, great attention has been paid to the studies on the photocatalytic systems promoting the solar-light-induced splitting of water into H_2 and 1/2O_2 because water and sunlight are abundant and such systems are free of the CO_2, emission.In this regard, we have focused on a well-known photosystem consisting of EDTA, tris(2,2′-bipyridine)ruthenium(II), methylviologen, and hydrogen-evolving catalysts, where particular Pt(II) complexes serve as the catalysts. Further, continuous efforts have also been made to develop the photo-hydrogen-evolving molecular devices consisting of photosensitizing rnthenium(II) centers and platinum(II)-catalyst centers. Various heteronuclear Ru(II)Pt(II) or Ru(II)_2Pt(II)_2 complexes have been prepared and evaluated. However we have long been unable to demonstrate the usefulness of such molecular devices. We recently succeeded in the preparation of the first Ru(II)Pt(II)-based molecular device which effectively catalyzes visible-light-induced EDTA-reduction of water into molecular hydrogen. It has been confirmed that the observed H_2-evolving activity is not due to any photodecomposition products.In the present study, to clarify the important factors which govern the photocatalytic activity of the Ru(II)Pt(II)-based molecular device, several other structural analogs have been prepared and their photo-H_2-evolving activities have been evaluated. As a result, the devices with peptide-linkage are found to evolve H_2 upon Xe-lamp irradiation in the presence of EDTA under Ar atmosphere. On the other hand, the compounds having two or more photosensitizing ruthenium(II) centers are found to be ineffective towards the photochemical H_2 generation, presumably due to the enhancement in intramolecular energy-transfer quenching processes. Less