合成不同型態的氧化亞銅粒子探討其用於電化學還原二氧化碳及光催化甲基橙之能力

Abstract

利用化學還原法可以生成顆粒大小均一度的氧化亞銅粒子。我們使用分子量為200的聚乙烯做為界面活性劑、抗壞血酸鈉做為還原劑，並藉由氫氧化鈉調整反應溶液的酸鹼度以獲得不同粒徑的氧化亞銅粒子。 將氧化亞銅粒子塗布在商用氣體擴散電極上，在電解液中輸入二氧化碳，由此觀察氧化亞銅的催化活性。為了瞭解催化劑的顆粒大小以及電解液對於電化學還原二氧化碳的影響，取用直徑分別為170、640及1570 nm的氧化亞銅粒子，選擇碳酸氫鈉、氫氧化鈉及氯化鈣做為電解液。我們得知氧化亞銅對於電化學還原二氧化碳具有一定的催化能力。持續通入二氧化碳以及-1.7 V的電壓5小時，640 nm 的氧化亞銅粒子在0.5 M 氫氧化鈉水溶液中可以獲得最高的電流 (-4.82 mAcm-2)。 探討氧化亞銅粒子做為光催化劑的光催化反應中，粒子形態及光源對光催化反應的影響，分別取用直徑為170、640及1570 nm的氧化亞銅粒子做為光催化劑，並改變光源，分別使用一盞150 W鹵素燈、四盞27 W白光日光及兩盞27 W白光日光燈。170 nm的氧化亞銅例子顯現最佳的光催化能力，在 150 W鹵素燈照射下6小時，有31.7 % 甲基橙降解。

Uniform Cu2O particles with various sizes and shapes were prepared by chemical reduction route, in which the polyethylene glycol (PEG) with average molecular weight of 200 was adopted as the surfactant, the L-ascrobic acid sodium (LAAS) was employed as the reducing agent, and the NaOH was used to adjust the pH value of the solution. We studied the electrochemical reductions of CO2 on Cu2O catalyzed gas diffusion electrodes to determine the catalytic abilities of the Cu2O. Three different sizes of the monodispersed Cu2O particles with diameters of 1570, 640, and 170 nm were explored as the catalysts. The NaHCO3, NaOH, and CaCl2 were chosen as the electrolytes. The Cu2O particles presented moderate catalytic abilities for electrochemical reduction of CO2. The highest average current density recorded was -4.82 mAcm-2 with Cu2O particles of average diameter of 640 nm in the 0.5 M NaOH electrolyte for 5 hours electrochemical reduction of CO2 at -1.7 V. The effect for the morphologies and light sources on the photocatalytic abilities of Cu2O was discussed. The Cu2O particles with diameters of 1570, 640, and 170 nm were chosen as photocatalysts. Photocatalytic degradation of methyl orange in an aqueous solution containing those Cu2O particles was investigated under one 150 W halogen lamp (yellow light), or two to four 27 W fluorescent lamp (white light). The photochemical process catalyzed by the Cu2O particles with a diameter of 170 nm under single 150 W halogen lamp demonstrated the highest photocatalytic ability, in which 31.7 % methyl orange was decolorized after 6 hours irradiation.