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Investigation of the Diffusion of Cr2O3 into Different Phases of TiO2 upon Annealing
ACS Applied Energy Materials ( IF 6.4 ) Pub Date : 2021-01-05 , DOI: 10.1021/acsaem.0c02270
Abdulrahman S. Alotabi 1, 2, 3 , Christopher T. Gibson 1, 3 , Gregory F. Metha 4 , Gunther G. Andersson 1, 3
Affiliation  

Chromium oxide (Cr2O3) can be used as a protective layer for photocatalysts to improve photocatalytic water splitting activity and is commonly photodeposited. However, it is not known how the conditions of the Cr2O3 formation affect the formation of the protective layer and potential diffusion into the substrate onto which Cr2O3 has been deposited. We have investigated the stability of Cr2O3 photodeposited onto the surface of different crystal phases of TiO2 with subsequent annealing at a range of temperatures up to 600 °C. X-ray photoelectron spectroscopy and synchrotron near-edge X-ray absorption fine structure were used to analyze the chemical composition of the sample, neutral impact collision ion scattering spectroscopy was used to study the concentration depth profile of the elements in the sample, and atomic force microscopy was used to investigate the morphology of the surface. Under annealing conditions, the Cr2O3 layer diffuses into the amorphous and anatase phases of TiO2 but remains at the surface of the rutile phase. This finding is attributed to differences in surface energy with Cr2O3 being higher in surface energy than the amorphous and anatase phases of TiO2 but lower in surface energy than the rutile phase of TiO2. Reduction of Cr2O3 to Cr metal was observed after annealing with no observation of the formation of higher oxidized forms of chromium oxide like CrO2 and CrO3. These findings are of general interest to researchers utilizing a protective overlayer to augment photocatalytic water splitting.

中文翻译:

退火过程中Cr 2 O 3向TiO 2不同相中扩散的研究

氧化铬(Cr 2 O 3)可用作光催化剂的保护层,以提高光催化水分解活性,通常被光沉积。然而,还不知道Cr 2 O 3形成的条件如何影响保护层的形成以及电势扩散到沉积有Cr 2 O 3的基板中。我们已经研究了光沉积在TiO 2不同晶相表面上的Cr 2 O 3的稳定性随后在最高600°C的温度范围内进行退火。X射线光电子能谱和同步加速器近边缘X射线吸收精细结构用于分析样品的化学成分,中性碰撞碰撞离子散射光谱用于研究样品中元素和原子的浓度深度分布力显微镜用于研究表面的形态。在退火条件下,Cr 2 O 3层扩散进入TiO 2的非晶相和锐钛矿相,但保留在金红石相的表面。该发现归因于表面能与Cr 2 O 3的差异其表面能高于TiO 2的无定形和锐钛矿相,但表面能量低于TiO 2的金红石相。退火后观察到Cr 2 O 3还原为Cr金属,没有观察到形成更高氧化形式的氧化铬,如CrO 2和CrO 3。这些发现对于利用保护层增强光催化水分解的研究人员来说是普遍感兴趣的。
更新日期:2021-01-25
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