Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
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Photocatalytic Decomposition of Rhodamin B over Bi2MoO6 Prepared Using Hydrothermal Process

수열합성법으로 제조된 Bi2MoO6에서 로다민 B의 광촉매 분해 반응

  • Hong, Seong-Soo (Department of Chemical Engineering, Pukyong National University)
  • Received : 2019.01.02
  • Accepted : 2019.01.23
  • Published : 2019.06.30
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Abstract

$Bi_2MoO_6$ catalysts were successfully synthesized using ethylene glycol monomethyl ether (EGME), glycerol (GL), ethylene glycol (EG), and water as solvents by a conventional hydrothermal method. The synthesized catalysts were characterized by XRD, DRS, BET, SEM, and PL, and we also investigated the photocatalytic activity of these materials for the decomposition of Rhodamin B under visible light irradiation. The XRD results revealed the successful synthesis of 12-18 nm, well-crystallized ${\gamma}-Bi_2MoO_6$ crystals with an Aurivillius structure regardless of solvent. In addition, the $Bi_2MoO_6$ catalysts prepared below $140^{\circ}C$ showed an amorphous phase; however, those prepared above $160^{\circ}C$ showed well-crystallized ${\gamma}-Bi_2MoO_6$ crystals. All the catalysts have a similar absorption spectrum from the ultraviolet region up to the visible region less than 470 nm. This result suggests that all the $Bi_2MoO_6$ catalysts are potential visible-light-driven photocatalysts. The $Bi_2MoO_6$ catalysts prepared using EGME as a solvent showed the highest photocatalytic activity. In addition, the $Bi_2MoO_6$ catalysts prepared at $180^{\circ}C$ showed the highest photocatalytic activity. The PL peaks appeared at about 560 nm at all catalysts and the excitonic PL signal was proportional to the photocatalytic activity for the decomposition of Rhodamin B. This suggests that the stronger the PL intensity, the larger the amount of oxygen vacancies and defects, and the higher the photocatalytic activity.

EGME, GL 및 EG와 물을 용매를 사용하여 $Bi_2MoO_6$ 산화물을 수열합성법으로 성공적으로 합성하였다. 이들 촉매들의 물리적 특성을 XRD, DRS, BET, SEM 및 PL 등으로 분석하였고 제조된 촉매들을 사용하여 가시광선 조사 하에서의 로다민 B의 광분해 반응에서의 활성을 조사하였다. XRD의 분석 결과에 의하면 대부분의 촉매들은 수열합성법에 의해 이 합성조건에서 용매의 종류와 관계없이 Aurivillius 구조를 가진 ${\gamma}-Bi_2MoO_6$의 결정화가 잘 이루어졌으며 12에서 18 nm의 크기를 나타내었다. 또한, 합성온도가 $140^{\circ}C$ 이하에서는 $Bi_2MoO_6$ 산화물의 특성피크가 잘 나타나지 않았으나, $160^{\circ}C$ 이상의 온도에서는 $Bi_2MoO_6$ 산화물의 특성피크가 잘 나타났다. 모든 촉매들은 자외선 영역부터 470 nm보다 낮은 파장의 가시광 영역에서 강한 흡수스펙트럼을 보여주고 있다. 이 결과는 $Bi_2MoO_6$ 산화물들이 가시광 영역에서도 광촉매 활성을 보여주고 있는 것을 의미한다. EGME를 용매로 사용하여 제조된 $Bi_2MoO_6$ 촉매가 가장 높은 광분해 활성을 나타내었고 $180^{\circ}C$에서 합성된 촉매가 가장 높은 광활성을 보여주었다. 모든 촉매들은 560 nm 부근에서 강하고 넓은 PL 흡수밴드가 나타났으며, 이 피크의 세기가 커질수록 광분해 활성이 증가하는 것으로 나타났다.

Keywords

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Figure 3. Diffuse reflectance absorption spectra of Bi2MoO6 catalysts prepared using different solvent (Vsolvent/VH2O = 50/50, synthesis temperature=180 ℃).

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Figure 4. SEM images of Bi2MoO6 catalysts prepared using different synthesis temperature (VEGME/VH2O = 50/50).

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Figure 5. PL spectra of Bi2MoO6 catalysts prepared using different solvent (Vsolvent/VH2O = 50/50, synthesis temperature = 180 ℃).

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Figure 1. X-ray diffraction patterns of Bi2MoO6 catalysts prepared using different solvent (Vsolvent/VH2O = 50/50, synthesis temperature = 180 ℃).

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Figure 2. X-ray diffraction patterns of Bi2MoO6 catalysts prepared using different synthesis temperature (VEGME/VH2O = 50/50).

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Figure 6. Photocatalytic decomposition of Rhodamin B over Bi2MoO6 catalysts prepared by different solvent; a) EGME, b) EG and c) GL (Vsolvent/VH2O=50/50, synthesis temperature=180 ℃).

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Figure 7. Photocatalytic decomposition of Rhodamin B over Bi2MoO6 catalysts prepared using different synthesis temperature (VEGME/VH2O = 50/50) : a) without catalyst, b) room temperature, c) 140 ℃, d) 160 ℃, e) 180 ℃, f) 200 ℃ and g) 240 ℃.

Table 1. The physical properties and photocatalytic activity of various Bi2MoO6 catalysts prepared using different solvent

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Table 2. The physical properties and photocatalytic activity of various Bi2MoO6 catalysts prepared using different synthesis temperature

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