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標題: TiO2/Ti薄膜電極結合外部迴路光電催化程序還原銀離子之探討
TiO2/Ti Thin Film Electrode Combined External Circuit Photoelectrocatalytic Process for Reducing Silver Ions
作者: 高肇郎
Kao, Chao-Lang
關鍵字: Photoelectrocatalytic;光電催化;Photocatalytic;Photoanode;Silver Recovery;光催化;光陽極;銀回收
出版社: 環境工程學系所
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經由SEM和XRD進行表面及晶體結構分析顯示:以常壓化學蒸氣沉降法製備TiO2/Ti光觸媒薄膜電極可獲得之晶體尺寸為30 nm,且晶型結構為銳鈦礦的TiO2光觸媒。當鍍膜時間為二小時,TiO2顆粒聚集情形較明顯。光應答試驗顯示:鍍膜六小時之TiO2/Ti光觸媒薄膜電極對365 nm的UV光光應答作用非常迅速,其光生電流密度可達7 μA/cm2。另外於結合外部迴路光催化及光電催化的實驗結果:在180 min光催化程序中,對於高濃度(1000 mg/ L)的銀離子還原效率可達70%;低濃度(108 mg/ L)的銀離子還原效率為93%,當照光時間延長至240 min,銀離子還原效率可達99.8%。在不同初始pH值條件下( 7、5、3),以pH 7時最有利於銀離子的光催化還原,而施加陽極偏壓對於銀離子還原效率是沒有幫助的;然而對醋酸降解方面則是有些微幫助(<10%)。

In this study, a nano-class TiO2/Ti thin-film electrode was made using the atmospheric pressure chemical vapor deposition (APCVD). The photoelectrocatalytic reaction system employed the TiO2/Ti thin film as anode and graphite rod as cathode. The electrode was combined with an external circuit and applied potential to study the efficiencies of silver ions reduction and acetic acid decomposition. The effects of pH, concentration of silver ions, concentration of acetic acid, applied potential, TiO2 surface analysis and electrochemical analysis.
Results of SEM images and XRD patterns of the TiO2/Ti thin-film electrode surface show that the thin film electrode made using the APCVD method can be as thin as 30 nm with the TiO2 photoelectric catalyst in anatase crystal form. More obvious agglomeration of TiO2 particles was observed by APCVD with 2 hours sprayed times. , Results of the light response study show that the electrode has a rapid response time under UV irradiation, and generation of photocurrent density with 7 μA cm-2. Additionally, results of the photocatalytic studies using the electrode combined with an external circuit in the photoelectrical catalytic studies to reduce silver ions reveal that with a reaction time of 180 min, the photocatalytic process will reduce 70% of silver ions in high-concentrated solution (1000 mg/L as Ag+) and 93% silver ions in low-concentrated solution (108 mg/L as Ag+). When the irradiation time is extended to 240 min, the silver reduction efficiency is as high as 99.8%. The solution pH 7 is favorable to the photoelectrical reduction of silver while the anode bias does not benefit the silver reduction efficiency but favors the decomposition of acetic acid. However, the process decomposes less than 10% of acetic.
The external circuit will transmit the photo-generated electrons to the cathode surface thus reducing the combination of electron and electronic holes at the anode surface. As the reduction of precious metals is concerned, the external circuit is capable of avoiding the metal deposition at the catalyst surface to cause catalyst poison or light shielding that are know to reduce the photo utilization efficiency.
其他識別: U0005-1412200804351200
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