| Summary: | 碩士 === 國立交通大學 === 生物科技系所 === 102 === There are many in the development of renewable energy sources, chosen the hydrogen as a potential research topic; causes the hydrogen can be a good energy carrier just likes electron. Otherwise, hydrogen has very higher heat of combustion per gram, more than the commonly used fossil fuels, including natural gas, coal and so on. On the other hand, combustion of hydrogen to produce water, and water could be raw material for hydrogen. This reaction is clean, non-pollution cycle!
Different from the steam reforming, electrolysis of water that commonly used high energy-consuming way to get hydrogen, using naturally occurring enzyme: hydrogenases. We mimic the catalytic center of hydrogenases that was called H-cluster which has two iron disulfide structures and completes the proton reduction in here. In the nature, whole of redox- reaction is beginning in the light-absorbing substances, called photosensitizer are excited by light then transferred electron to the H-cluster. And the protons will reduction by this excited electron. According to this photosensitizer and H-cluster model, we tried to use an artificially synthesized bridge (linker) that connected between the potosensitizer and H-cluster. In this Photosensitizer-linker-cluster (P-L-C) model, we expected that it can accelerate transfer excited electron to catalytic center from photosensitizer, which has the better efficiency than before. And we use NMR, MS and FT-IR to identify the structure, use GC-TCD to compare the turnover number (TON) and turnover frequency (TOF) with the hydrogen generation.
The first synthesized P-L-C model was Pt-L-Fe2S2 which the Pt(tpy) as photosensitizer and Fe2S2 as the catalyst, the second synthesized P-L-C model was used Ru2S2 to replacement the Fe2S2 and became Pt-L-Ru2S2. The synthesized Pt-L-Fe2S2 and Pt-L-Ru2S2 were investigated using different proton sources, such as water and formic acid in photocatalytic hydrogen production. In addition, we evaluate the effects of a series of electron-donating phosphine ligands additions on the photocatalytic system for hydrogen production to investigated. In the organic phase, with formic acid as a proton source, Pt-L-Ru2S2 showed higher efficiency of hydrogen evolution than Pt-L-Fe2S2. In the presence of P-ligands, the hydrogen yield obtained from the P-ligands with electron donating functional group is higher than the P-ligands with electron withdrawing functional group in Pt-L-Ru2S2 model, but the affect of P-ligands’ influence was not significant in Pt-L-Fe2S2 model. On the other hands, the different equivalents P-ligands gave the Pt-L-Ru2S2 more hydrogen produced which was the 3 equiv of the P(o-Tol)3 with Pt-L-Ru2S2 had 13057.8 μmol hydrogen produced with 13057.8 TON (TOF = 2673.9 h-1). The others photosensitizers (Ru, Ir-based) were added with no-connecting Ru2S2 in photocatalytic hydrogen production to compared the potential of the Ru-L-Ru2S2 and Ir-L-Ru2S2.
In aqueous phase of Pt-L-Ru2S2 model, the results showed that AA was better than TEA as the electron donor. Besides, the affect of P-ligands’ electron donating/withdrawing function group in aqueous phase were similar to in organic phase, but P-ligands couldn’t elevated the hydrogen produced.
Summary, the efficiency of hydrogen production is better than in previous studies. The detailed catalytic mechanism of these artificial biomimetic P-L-C models might be discussed and studied. In the future, the P-L-C model will be promising catalysts in the light-driven hydrogen production industry.
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