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Correlations among Structure, Electronic Properties, and Photochemical Water Oxidation: A Case Study on Lithium Cobalt Oxides
ACS Catalysis ( IF 11.3 ) Pub Date : 2015-05-22 00:00:00 , DOI: 10.1021/acscatal.5b00078
Hongfei Liu 1 , Ying Zhou 2 , René Moré 1 , Rafael Müller 1 , Thomas Fox 1 , Greta R. Patzke 1
Affiliation  

Construction of {M4O4} motifs is an effective design paradigm for molecular polyoxometalate- and oxide-based water oxidation catalysts (WOCs). However, the mechanisms beneath this bioinspired design strategy remain a topic of intense debate. The two modifications of LiCoO2 with spinel-type and layer structures are exceptionally versatile model systems to explore the correlations among structure, electronic properties, and photochemical water oxidation. The electronic properties of both LiCoO2 modifications are tunable through delithiation while the basic structural frameworks are maintained. This provides a unique opportunity to assign the respective influence of structures and electronic properties on the water oxidation properties. While spinel-type LiCoO2 with {Co4O4} cubane motifs is active for photochemical water oxidation, the layered modification without cuboidal structural elements is nearly inactive. Here, we demonstrate that the water oxidation performance of both modifications can be significantly improved through chemical delithiation. A wide range of analytical methods were applied to investigate the transition of electronic properties upon delithiation, and a direct correlation between enhanced hole mobility and improved water oxidation activity was established. The difference in water oxidation activities between the two structural modifications was further linked to the role of {Co4O4} cubane motifs in constructing 3D Co–O–Co networks with expanded hole transfer paths. Thus, the promoting effects of both delithiation and {Co4O4} cubane motifs on water oxidation can be consistently explained by enhanced hole mobility.

中文翻译:

结构,电子性质和光化学水氧化之间的关系:以钴酸锂为例

{M 4 O 4 }主题的构建是基于分子多金属氧酸盐和氧化物的水氧化催化剂(WOC)的有效设计范例。然而,这种受生物启发的设计策略的机制仍然是激烈争论的话题。具有尖晶石型和层状结构的LiCoO 2的两种修改形式是非常通用的模型系统,用于探索结构,电子性能和光化学水氧化之间的关系。LiCoO 2的电子性质在维持基本结构框架的同时,可以通过取消修饰来调整修改。这提供了独特的机会来分配结构和电子性能对水氧化性能的影响。而尖晶石型LiCoO 2与{Co 4 O 4}古巴图案对于光化学水氧化具有活性,没有立方体结构元素的分层修饰几乎没有活性。在这里,我们证明了两种修饰的水氧化性能都可以通过化学脱锂得到显着改善。广泛的分析方法被用于研究脱锂时电子性能的转变,并建立了增强的空穴迁移率和改善的水氧化活性之间的直接关系。两种结构修饰之间水氧化活性的差异还与{Co 4 O 4 }古巴图案在构建具有扩展的空穴传输路径的3D Co-O-Co网络中的作用有关。因此,脱锂和{Co水氧化的4 O 4 }古巴图案可以通过提高空穴迁移率来一致地解释。
更新日期:2015-05-22
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