新穎光觸媒光電性質及光分解水表現之研究與探討

管狀結構相較於粉末結構有更大的比表面積，陽極處理置備二氧化鈦奈米管具有低價格、高效率、排列有序和製程簡單等優點，本實驗於鈦金屬箔片置備二氧化鈦奈米管以用來進行光催化反應，為了於二氧化鈦奈米管中產生氧缺陷以降低其能隙值使其在可見光下反應，因此將二氧化鈦米管於還原氣氛(99%N2+1%H2)中，溫度400℃到750℃進行退火。吸收光譜顯示二氧化鈦奈米管於空氣和還原氣氛退火之臨界吸收波長皆有藍移(blue shift)之現象，且溫度從600℃到750℃，其吸收曲線於可見光區皆有上揚之趨勢，其原因為氧缺陷存在於二氧化鈦奈米管中，且溫度對於二氧化鈦奈米管吸收曲線的影響大於氣氛，溫度為600℃時，產生氧缺陷的主要原因為相轉變導致結構上的mismatch，溫度為700℃和750℃時，由於氧的擴散速率變快，因此會往底層的鈦擴散並與其行氧化反應。二氧化鈦奈米管其光電流密度和IPCE於可見光照射下亦有表現，且XPS分析顯示有氧缺陷的存在，這些都證明了二氧化鈦奈米管中氧缺陷的存在。從I-V curve 結果顯示，二氧化鈦奈米管於空氣和還原氣氛退火溫度600℃持溫4hr，於電壓1V時光電流密度最大，且其光轉氫效率為1.8~2.1%。 (Ag0.75Sr0.25)(Nb0.75Ti0.25)O3光觸媒分別以Ag2O、Nb2O5、SrCO3和 TiO2四種原始粉末以及Ag2O、Nb2O5和SrTiO3三種原始粉末去混，其XRD皆以AgNbO3為主要結構，從吸收光譜曲線可知，於三種混和四種混之(Ag0.75Sr0.25)(Nb0.75Ti0.25)O3，加入分散劑之結果皆造成其微結構為porous的表現，其吸收曲線對光的吸收值有明顯之提升。

關鍵字

光觸媒；光電性質；光分解水；二氧化鈦奈米管

並列摘要

Large surface area nanotubes have been considered to be an effective structure for sufficient active point promotion for photocatalyst. In this research, anodization of Ti foils was utilized for ordered arrays of TiO2 nanotubes photocatalyst fabrication. High temperature annealing (600°C to 750°C) under reduction (99%N2/1%H2) and ambient atmosphere was applied for oxygen vacancies generation for which the photocatalytic reaction to occured. Progressing blue-shift was appeared in UV-Vis spectra which revealed the band gap evolution under different annealing temperature, moreover, gradually rise in optical density at visible region (from 400 nm to 800 nm) was observed in the cases of 600℃ to 750℃ annealed samples. X-ray diffraction (XRD) analysis results demonstrated phase transition of TiO2 nanotubes from anatase to rutile with respected to different annealing temperature, decreasing in intensity of diffraction peaks about Ti foil was also observed. Oxygen concentration was found to increase with depth by XPS depth profile observation. To the above regards, oxygen vacancies were proposed to be generated during annealing treatment by phase transition caused lattice mismatch and oxygen atoms diffusion, especially in high temperature annealed cases. To the aspect of photocatalystic activity, greatest current density with respect to given potential was found to be 1 V for TiO2 nanotubes annealed under both reduction and ambient atmospheres for 4 hrs at 600℃, and the photon-to-hydrogen generation efficiency monitored at this potential was in the range of 1.8~2.1%. To extend the working wavelength of photocatlayst to visible region, (Ag0.75Sr0.25)(Nb0.75Ti0.25)O3 photocatalyst was fabricated by Ag2O, Nb2O5, SrCO3 and TiO2 mixed powders. Surfactant (Darvan C) was conditionally used to facilitate the powder mixture before sintered. For comparison, photocatalyst composed by Ag2O, Nb2O5 and SrTiO3 was also preformed. According to XRD testing results, AgNbO3 was found to be the dominant phase in both cases. UV/Vis spectra demonstrated (Ag0.75Sr0.25)(Nb0.75Ti0.25)O3 photocatalyst fabricated by three and four powders mixture with surfactant got higher optical intensity in absorption for which would further enhance photocatalytic performance in visible region.

並列關鍵字

photocatalyst ； IPCE ； TiO2 nanotubes ； efficiency

參考文獻

29. 鄭哲岳，「在含氟甘油電解液中陽極氧化鈦箔製備二氧化鈦奈米管」，國立台灣大學材料科學與工程研究所碩士論文，民國98年。

8. I. Tsuji, H. Kato, H. Kobayashi and A. Kudo, "Photocatalytic H2 evolution reaction from aqueous solutionsover band structure-controlled (AgIn)xZn2(1-x)S2 solid

1. M. Kitano, M. Matsuoka, M. Ueshima and M. Anpo, "Recent developments in titanium oxide-based photocatalysts." Applied Catalysis A: General, 325(2007)1-14.

2. D. Wang, T. Kako and J. Ye, "Efficient photocatalytic decomposition of acetaldehyde over a solid-solution perovskite (Ag0.75Sr0.25) (Nb0.75Ti0.25)O3 under visible-light irradiation." Journal of the American Chemistry Society, 130(2008)2724-2725.

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新穎光觸媒光電性質及光分解水表現之研究與探討

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