나노크기의 Mo/Ti 혼합광촉매 제조 및 특성조사

윤우석; 설용건; 주현규; 전명석; 이태규; Woo Sug Yoon; Yong Gun Shul; Hyunku Joo; Myung Seok Jeon; Tai Kyu Lee

HWAHAK KONGHAK, Vol.38, No.3, 343-347, June, 2000

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나노크기의 Mo/Ti 혼합광촉매 제조 및 특성조사

Preparation and Characterization of Nano-sized Mo/Ti Photocatalyst

윤우석, 설용건 , 주현규 ¹, 전명석 ¹, 이태규 ^{1, †}

연세대학교 화학공학과
¹한국에너지기술연구소 태양에너지변환연구센터

Woo Sug Yoon, Yong Gun Shul , Hyunku Joo¹, Myung Seok Jeon¹, and Tai Kyu Lee^{1, †}

Department of Chemical Engineering, Yonsei University, Korea
¹Photocatalysis and Photoelectrochemistry Research Center, Korea Institute of Energy Research, Korea

E-mail:

초록

본 실험에서는 광촉매의 빛의 흡수파장을 가시광선 영역으로 이동시키고, 효율을 향상시키기 위하여 Mo⁵⁺를 0-2.5mol%의 농도범위로 TiO₂에 첨가한 혼합광촉매인 Mo/Ti를 제조하였다. 제조한 Mo/Ti 혼합광촉매의 특성을 UV/VIS, TEM-EDP, XRD, EDAX, 그리고 XPS를 사용하여 관찰하였으며, dichloroacetic acid(DCA)의 공분해 반응속도와 actinometry을 통한 빛의 세기(2.68μE/sec) 측정을 통하여 농도별 혼합광촉매의 photonic efficiency를 조사하였다. TEM-EDP와 XRD pattern의 관찰결과, 입자의 지름이 약 4nm인 anatase TiO₂임을 확인하였으며, Mo⁵⁺의 첨가량이 증가할수록 Mo/Ti의 빛의 흡수파장 onset이 순수 TiO₂와 비교하여 red-shift되는 것이 밝혀졌다(2.5% Mo/Ti의 경우 순수 TiO₂보다 약 0.22 eV 감소). EDAX결과로부터 제조된 혼합광촉매가 이론적인 Mo의 농도와 근사함을 확인하였으며, XPS로 Mo(V)의 존재를 관찰할 수 있었다. Photonic efficiency는 본 실험조건하에서 0.5mol% Mo/Ti의 경우 0.28로 최대이었는데, 이는 다양한 혼합광촉매에서 공통적으로 나타나는 경향으로 dopant의 함유량이 증가할수록 점진적으로 전자트랩 효과에 의하여 광촉매 효율이 상승하다가, 적정농도 이상이 첨가되는 경우에는 오히려 전자/정공 트랩장소간의 거리 감소로 인하여 전자-정공의 재결합이 촉진되기 때문이다. 열처리 온도가 증가할수록 측정된 photonic efficiency는 감소하였는데, 이는 열처리 후 촉매입자들의 agglomeration에 의한 비표면적 감소와 광화학적 비활성인 rutile 결정의 생성이 주된 원인으로 분석되었다.

In this study, molybdenum-doped TiO₂(Mo/Ti) mixed oxide nanoparticles were prepared with the Mo⁵⁺ content varying from 0 up 2.5 mol% to shift the absorption onset into the visible part, and to enhance the efficiency by retarding the e^--h⁺ recombination. They were characterized by UV/VIS, TEM-EDP, XRD, EDAX, and XPS. Photonic efficiency was also investigated with the degradation rate of dichloroacetate(DCA) and light intensity measured by actinometry(2.68 μE/sec). TEM-Electron diffraction and X-ray diffraction patterns showed that particles were in the form of anatase with the diameter of ca. 4 nm. Appreciable red-shift in UV/VIS absorption sepctra was observed with the addition of Mo, starting UV/VIS absorption in the case of 2.5%Mo/Ti at around 0.22 eV less than in nano-sized pure TiO₂(around 3.42eV). EDAX verified that the amount of Mo in the prepared mixed oxides was obtained as wished and XPS revealted that Mo existed in TiO₂ lattic. Measured photonic efficiency turned out to be increased up to 0.28 at 0.5mol%^ Mo, and then decreased as Mo content kept increasing higher than that. This was explained by the changing prevailing phenomena-electron trapping and recombination - as the amount of dopant increased.

Keywords:Photocatalyst;Q-size Particle;Mixed Oxides(Mo/Ti);Photonic Efficiency

[References]

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Joo HK, Jeon MS, Lee TK, J. KSEE, 21(6), 1231 (1999)
Kim DH, Lee TK, Kim KB, Lee SW, Korean J. Mater. Res., 6(3), 282 (1996)
Yoon JK, Kang JW, Lee TK, Jeon MS, Joo HK, J. KSEE, 21(5), 1003 (1999)
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Jeon MS, Lee TK, Kim DH, Joo HK, Kim HT, Sol. Energy Mater. Sol. Cells, 57 (1999)
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[Related Articles]

[1] Lee TK, Joo HK, Shul YG, Choi W, Choi JH, in Auh, C.M. and Lee, K.W.(Eds.), "Photochemical Conversion and Applications," KISTEP 99-05 (1999)

[2] Joo HK, Jeon MS, Lee TK, J. KSEE, 21(6), 1231 (1999)

[3] Kim DH, Lee TK, Kim KB, Lee SW, Korean J. Mater. Res., 6(3), 282 (1996)

[4] Yoon JK, Kang JW, Lee TK, Jeon MS, Joo HK, J. KSEE, 21(5), 1003 (1999)

[5] Choi WY, Termin A, Hoffmann MR, J. Phys. Chem., 98(51), 13669 (1994)

[6] Choi WY, Termin A, Hoffmann MR, Angew. Chem., 106, 1148 (1994)

[7] Choi W, Ph.D. Dissertation, California Institute of Technology, Pasadena, U.S.A. (1996)

[8] Bahnemann DW, in E. Pellizzetti and M. Schiavello(Eds.), "Photochemical Conversion and Storage of Solar Energy," Kluwer Academic Publisher, Netherlands (1991)

[9] Bahnemann DW, Israel J. Chem., 33, 115 (1993)

[10] Jeon MS, Lee TK, Kim DH, Joo HK, Kim HT, Sol. Energy Mater. Sol. Cells, 57 (1999)

[11] Bahnemann DW, Cunningham J, Fox MA, Pelizzetti E, Pichat P, Serpone N, in G.R. Helz, R.G. Zepp, and D.G. Crosby(Eds.), "Aquatic and Surface Photochemistry," Lewis Publishers (1994)

[12] Bockelmann D, Lindner M, Bahnemann D, in E. Pellizzetti (Ed.), "Fine Particles Science and Technology," Kluwer Academic Publishere, Netherlands, 675 (1996)

[13] Hoffmann MR, Martin ST, Choi WY, Bahnemann DW, Chem. Rev., 95(1), 69 (1995)

[14] Kormann C, Bahnemann DW, Hoffmann MR, J. Phys. Chem., 92, 5196 (1988)

[15] Kikkawa H, O'Regan B, Anderson MA, J. Electroanal. Chem., 309, 91 (1991)

[16] Powder Diffraction File. Setd 21-22; JCPDS: Swarthmore, Vol. PDIS-22iRB, 21-1272 (1980)

[17] Cullity BD, "Elements of X-Ray Diffraction," 2(nd) ed., Addison Wesley, MA (1978)

[18] Gratzel M, "Heterogeneous Photochemical Electron Transfer Reaction," CRC Press, Boca Ration, Florida, U.S.A. (1987)

[19] Gratzel M, in Serpone, N. and Pelizzetti, E.(Eds.), "Photocatalysis: Fundamentals and Application," John Wiley & Sons, New York (1989)