氫化之二氧化鈦奈米管於光裂解水製氫之應用

Abstract

在本研究中，我們利用簡易電化學陽極氧化法，於高純度鈦金屬表面形成其奈米管狀的氧化結構，之後嘗試了解氫化對其在光裂解水製造氫氣應用上的影響。並使用SEM、XRD、XPS與UV-Vis進行儀器分析。 我們使用AM 1.5太陽光模擬光源，以電化學方法量測其效率，同時我們使用TiCl4進行奈米管的表面修飾、與再退火程序來進行效率的改進。最後再將個別最佳化條件合併探討，並整合出最終的最佳條件。 在最後的效率增進上，我們得到106%的相對提升(0.169% →0.348%)。我們發現的效率增進原因有以下兩點：一方面是因為氫化與再退火過程都可以明顯改善二氧化鈦奈米管的晶相結構，使其電子-電洞對再結合的機率降低，有效的提升水裂解的光電流大小；二方面是因為在氫化過程中，可以改變二氧化鈦銳鈦礦的能隙，增加其在紫外光與可見光的光吸收，而使相對激發的光電子數量增加，進而增加水裂解效率。

In this study, we employed a facile electrochemical anodization method to prepare for TiO2 nanotubes on high purity titanium foils, and attemped to study the effect of hydrogenation of TiO2 nanotubes on water splitting. All samples were characterized by SEM, XRD, XPS and UV-Vis analyses. We used an AM 1.5 solar simulator as the light source and measured the efficiency of water splitting by an electrochemical method. We also treated the substrates with TiCl4 solution and re-annealed and optimized them for water splitting applications. We obtained a 106% improvement in relative efficiency (from 0.169% →0.348%), which may be attributed to two factors: (1) Improvement in the crystallinity of TiO2 nanotubes by the hydrogenation and re-annealing process, which may reduce the electron-hole recombination rate; (2) Reduction in the band gap of TiO2 by hydrogenation and thus increasing light absorption in the UV and visible regions. Both factors could help enhance the overall water splitting efficiency.