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Search / Korean Journal of Chemical Engineering
HWAHAK KONGHAK,
Vol.38, No.3, 343-347, 2000
나노크기의 Mo/Ti 혼합광촉매 제조 및 특성조사
Preparation and Characterization of Nano-sized Mo/Ti Photocatalyst
윤우석, 설용건, 주현규, 전명석, 이태규
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
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