氧化物光電極之載子動力學於光電化學水分解的應用

Charge Carrier Dynamics of Metal Oxide Photoelectrodes for Photoelectrochemical Water Splitting

由於石化燃料過度使用，造成顯著的環境氣候變遷與溫室效應，為降低人類對於石化燃料的過度依賴，發展再生能源達到「淨零排放」，減低溫室效應而達到氣候中和，是目前全球產學研各界努力的方向。其中，氫能源具有很高的燃燒熱且對環境友善，是一種相當有潛力的再生能源，而光電化學水分解(Photoelectrochemical (PEC) water splitting)，可透過給予低偏壓並搭配太陽能，驅動水分解反應產生氫能源，是備受注目的太陽燃料(Solar fuel)技術。PEC系統中利用半導體材料作為光電極，而半導體之能隙與能帶電位性質，其分別主宰對於太陽光的吸收能力與在水分解反應系統中的氧化還原能力，影響實際的太陽能轉換氫氣效率(solar-to-hydrogen efficiency, hSTH)。而金屬氧化物半導體材料可作為PEC系統中之光陽極，在適當電位驅動下，配合太陽能的輸入即可進行PEC的陽極反應，即水分解中的氧氣析出反應(oxygen evolution reaction, OER)。因此，金屬氧化物半導體電極對於PEC系統的hSTH，扮演了相當重要的角色，本文針對目前在PEC系統中，金屬氧化物二氧化鈦(TiO2)與釩酸鉍(BiVO4)光陽極進行介紹，並探討其載子動力學影響PEC水分解反應之效率與進展。

The significant environment climate change and greenhouse effects due to the overuse of fossil fuel, resulting in the highly emission of CO2. The reduce of CO2 concentration in the atmosphere of earth by reducing the over-reliance of fossil fuel to achieve climate neutral is an important global issue of“Net Zero Emissions”. Photoelectrochemical (PEC) cells have been demonstrated as a sustainable and green technology to produce hydrogen (H2) energy by splitting water, which also called“solar fuel”. Among this technology, the intrinsic energy band structures of semiconductor photoelectrodes serve the important role in capturing solar energy and converting it into electron-hole pairs for the reduction and oxidation of water and the solar-to-hydrogen efficiency (hSTH). Typically, the performance of metal oxide photoanodes would dominate the efficiency of PEC oxygen evolution reaction (OER) with suitable applied potential under solar light irradiation. Herein, the metal oxide photoanodes, TiO2 and BiVO4, would be introduced and discussed that the effects of their charge carrier dynamics on the efficiency and progress in PEC water splitting.