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.

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

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