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Facile Solution Synthesis of Colloidal CeO2 Quantum dots For Enhanced Photoelectrochemical and Anti-corrosion performances

  • 서동현 (Seo Donghyun, 아주대학교 일반대학원)

초록/요약

In this work, synthesized colloidal CeO2 quantum dots (Ce-QDs) via a facile aqueous solution method using citric acid as a chelating/stabilizing agent and ammonia as an oxidant. The Ce-QDs with an average size of 1.8, 2.3, and 3.0 nm were well-dispersed in the aqueous solution with high stability. The photoelectrochemical water-splitting activity of the Ce-QDs films was investigated. The colloidal Ce-QDs were spin-coated onto BiVO4 (BVO) photoanode, allowing homogeneous and uniform deposition of Ce-QDs on the BVO (Ce-QDs/BVO) photoanode. This Ce-QDs/BVO photoanode exhibited enhanced photoelectrochemical activity, achieving a high photocurrent density of 4.0 mA/cm2 with CoOx co-catalyst deposition under simulated sunlight illumination, which is eight times higher than pristine BVO photoanode (~0.6 mA/cm2). Besides, this structure showed much improved stability, whereas BVO had 70% stability loss, with highest oxygen evolution faradaic efficiency of 89% at 1.23 V versus the reversible hydrogen electrode in the phosphate buffer solution (pH 7.4). Besides, the Ce-QDs were applied to AZ31B magnesium alloy to investigate its corrosion inhibition behavior. I found that the corrosion resistance of Ce-QDs/AZ31B increased by surface passivation, thereby reducing corrosion of AZ31B to a greater extent. These results demonstrate that synthesis methodology is promising for the cost-effective and large-scale synthesis of Ce-QDs with uniform size for diverse (photo)electrochemical and anti-corrosion applications.

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초록/요약

이 연구에서는 구연산을 킬레이트 및 안정제로 암모니아수를 산화제로 사용하여 용액공정으로 쉽게 CeO2 quantum dot (Ce-QDs) 콜로이드 용액을 합성했다 합성된 Ce-QD는 물 속에서 매우 안정적으로 분산되었고 , 각각 평균 1.8, 2.3, 3.0 nm 의 크기로 광전기화학 수전해 photoelectrochemical water splitting, PEC water splitting) 에 사용되었다. 콜로이드 Ce-QDs 는 BiVO4 (BVO) 광음극에 스핀 코팅 기법을 사용하여 균일하게 증착 되었다 Ce-QDs 가 증착 된 BVO (Ce-QDs/BVO) 는 인공 태양 조명 아래에서 CoOx 촉매와 함께 사용함으로써 BVO 전극 (~0.6 m A/cm 2 보다 약 8 배 높은 4.0 mA/cm2의 높은 광전류밀도를 달성하였다 게다가 이 전극은 PBS 전해질에서 진행한 안정성 실험에서 약 70 % 의 손실을 보였으며 1.23 V vs. RHE 에서 89 % 의 높은 산소 생산 효율을 보여주었다 뿐만 아니라 Ce-QDs 는 금속의 부식을 방지하기 위해서도 사용되었으며, AZ31B 마그네슘 합금에 적용하였다 AZ31B 에 Ce-QDs 가 증착 됨으로써 3.5 wt% NaCl 전해질에서 부식속도 감소 부식 저항 증가 등의 효과를 보여주었다 이러한 결 과를 통해 이 연구에 사용된 Ce-QDs 합성 방법은 비용 대면적 등에 효과적이며 PEC, 방식 등 다양한 분야에 적용이 가능함을 보여주었다

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목차

1. Introduction １
1.1 Cerium oxide quantum dots (CeO2 QDs) １
1.2 Photoelectrochemical (PEC) water splitting １
1.3 Bismuth vanadate (BiVO4) photoanode ２
1.4 Anti-corrosion ３
1.4.1 Properties of AZ31B magnesium alloy ３
1.4.2 Various method of anti-corrosion ３
2. Experimental ３
2.1 Synthesis of colloidal CeO2 QDs ３
2.2 Synthesis of BiVO4 (BVO) photoanode ４
2.3 Pre-treatment of AZ31B magnesium alloy ５
2.4 CeO2 QDs layer coating ５
2.5 Characterizations and measurements ５
2.5.1 Characterization ５
2.5.2 PEC measurement and analysis ６
2.5.3 Corrosion test ６
3. Results and discussions ７
3.1 Synthesis of CeO2 QDs ７
3.2 Morphology and crystal properties １１
3.2.1 Effect of synthesis temperature of CeO2 QDs １１
3.2.2 Characterization of BVO photoanode １４
3.2.3 SEM and XRD analyses of Ce-BVO １６
3.3 Optical properties and band alignment １８
3.3.1 Optical properties according to the size of Ce-QDs １８
3.3.2 Optical properties of Ce-BVO ２０
3.4 PEC performance of Ce-QDs/BVO photoanode ２２
3.4.1 Optimization of Ce-QDs/BVO photoanode with LSV curve ２２
3.4.2 Stability and faradaic efficiency of Ce-BVO ２４
3.5 Electrochemical analysis of Ce-QDs/BVO photoanode ２６
3.5.1 EIS analysis of Ce-QDs/BVO ２６
3.5.2 Transfer and transport efficiency of photoanode ２８
3.5.3 Electrochemically active surface area of photoanode ２９
3.6 Anti-corrosion properties of Ce-QDs/AZ31B ３１
3.6.1 Anti-corrosion performance with Tafel plot study ３１
3.6.2 Corrosion test of Ce-QDs/AZ31B ３２
3.6.3 EIS analysis ３３
3.7 Surface analysis of Ce-QDs/AZ31B ３５
4. Conclusion ３７
5. Reference ３８

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