以溶凝膠製得Pt/SrTiO3:Rh在鈰離子傳遞媒介下雙胞膜反應器進行可見光水分解

Abstract

隨著工業社會對於能源的需求日益增加，利用太陽光能來進行水分解製氫反應，是一種可生產潔淨無污染之替代能源方式。Z-scheme雙觸媒系統是利用兩種不同之光觸媒，分別進行產氫與產氧之半反應，並利用不同的離子傳遞媒介傳遞電子與電洞，達到全反應的效果。本實驗室先前的研究指出，利用預處理過的Nafion薄膜將不同的反應觸媒系統隔開，不僅能夠藉由擴散效應傳遞離子媒介，也能達到分離氫氣與氧氣的效果，進而提升產量。本實驗使用溶凝膠法製得Pt/SrTiO3:Rh作為產氫觸媒，發現在pH值為1.5下觸媒活性最佳，在10vol%甲醇水溶液中進行可見光產氫活性測試，6小時內產氫量均可達到10 µmol/gcat以上，活性較固態熔融法和水熱法為佳，再以 BiVO4作為產氧觸媒，置入分離式雙胞膜反應器中，以Ce4+/Ce3+為電子傳遞媒介於水溶液中，利用Nafion 陽離子交換膜隔開兩觸媒，以可見光照射反應器進行水分解，達到氫氧分離的效果。實驗以300W氙燈作為可見光源，使用以Ce4+前處理的Nafion 薄膜進行反應，可達到一定的產氫效果，並且符合H2:O2=2:1的水分解化學當量比。溶凝膠法Pt/SrTiO3:Rh搭配光沉積法製備，產氧端觸媒使用液相合成法製備BiVO4，而使用雙胞膜反應器，由於減少了氫氧逆反應的機會，可提升產氫的速率，將兩邊觸媒分開也可解決觸媒之間混合在一起之光源競爭吸收問題，並且期望測試鈰離子傳遞媒介存在下的最佳反應條件，以期提升產氫效能。

With the increasing demand for energy in the industrial society, using solar energy to produce hydrogen by water splitting is an alternative clean and pollution-free way to produce energy. Z-scheme system is the use of two different kinds of photocatalysts to do half-reaction of water splitting , respectively, and the use of different transmission medias to transmit electrons and holes, and finally completes the whole reaction. Previous studies in our laboratory point out that the use of pretreated Nafion membrane to separate the different reaction catalyst systems, not only to pass through ion transfer mediator by diffusion effect, but also to separate hydrogen and oxygen, and thus enhance the production. In this study, first we use sol-gel method to produce Pt/SrTiO3:Rh catalyst as hydrogen production, then put it in 10vol% methanol aqueous solution to do the test of hydrogen production activity in visible light , and hydrogen production can reach 10 µmol / gcat within 6 hours. We found that at pH 1.5 the catalytic activity is the best. Producing SrTiO3 by sol-gel method can get higher activity than using solid-state method and hydrothermal method. Secondly, we add BiVO4 as oxygen production into the twin membrane reactor, and Ce4+/Ce3+ as ion transfer mediators in the aqueous solution, and use Nafion cation exchange membrane to separate the two catalysts to do water decomposition in visible light. Besides , the membrane can separate hydrogen and oxygen. In our study we use 300W xenon lamp as the visible light source and Ce4+ pre-treated Nafion membrane to separate two sides of half-reaction. The result is that the hydrogen production can be achieved certain level, and that in line with H2/O2 = 2 stoichiometric decomposition of water. Pt/SrTiO3:Rh is prepared by Sol-gel method with light deposition method, and BiVO4 is produced by liquid phase synthesis. The use of double-membrane reactor can reduce the chance of reversing reaction of hydrogen and oxygen, therefore it enhance hydrogen production rate. Separating two sides of the catalysts can also solve the problem of competitive absorption of light. We expect to test the best reaction conditions in the presence of cerium ions in order to improve the hydrogen production performance.