光催生物質選擇性氧化的過程，利用了豐富的太陽光生產高經濟價值的產物，是一道節省能源並對環境友善的製程。我們嘗試開發吸收可見光的光陽極應用在醇類的選擇性氧化上，所選定的材料為BiVO4，本研究首先著重在改善BiVO4光陽極，探討了三種方法對光電流及穩定性提升的情形，第一個方法是預想透過鹼液熱處理合成Bi2O3/BiVO4 p-n junction，雖然沒有成功合出此結構，但在1.23 V vs. RHE下光電流仍提升了29%；第二個方法為裝載MnOx共觸媒，成功提升了低偏壓區的光電流，但高偏壓區的光電流卻出現被抑制的情形，代表共觸媒的裝載能夠促進反應動力學，但也存在界面的問題需要克服；第三個方法則是塗佈TiO2保護層，在1.23 V vs. RHE下光電流提升了15%，而TiO2/BiVO4的穩定性則比前述兩個方法為佳。我們也透過在未添加或添加犧牲試劑的電解液中量測IPCE，個別探討BVO4光陽極三個部份的效率值，分別為吸光效率(ηabs)、光生電子─電洞對分離效率(ηbulk)以及半導體/電解液界面電荷轉移效率(ηsurf)。;The process of photocatalytically selective oxidation of biomass, which is eco-friendly and energy saving, harvests abundant sunlight to produce high value-added chemicals. We aim to develop a photoanode using BiVO4 as target material to absorb visible light in application of selective oxidation of alcohols. This study first focus on improving BiVO4 photoanode, and discuss three methods for improving photocurrent densities and stability. First, we attempt to fabricate Bi2O3/BiVO4 p-n junction through an alkaline thermal treatment. Although Bi2O3 phase wasn’t observed , the photocurrent densities still raised by 29% at 1.23 V vs. RHE compared with that of pristine BiVO4. Second, the enhancement of photocurrent densities in the low bias region was attained during loading MnOx cocatalyst on BiVO4 photoanode surface, but the photocurrent densities in the high bias region was suppressed. This result indicated that loading cocatalyst can promote the reaction kinetics, but charge recombination might happen between the interfaces. Last, coating crystalline TiO2 as a protection layer enhanced the photocurrent density by 15% at 1.23 V vs. RHE. And TiO2/BiVO4 photoanode dominated stability than aforementioned photoanodes. In addition, we calculated IPCE of BiVO4 photoanode with or without sacrificial reagent in electrolyte which is capable of measurement of absorption efficiency (ηabs), electron-hole separation efficiency (ηbulk) and semiconductor/electrolyte interface charge transfer efficiency (ηsurf) of BiVO4 photoanode, respectively.
