​南开AFM: 稀土诱导CoO6八面体畸变，助力RuO2催化水氧化

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低成本和可调谐的钙钛矿氧化物(ABO3)是贵金属基OER催化剂的有希望的候选者。然而，由于电导率低、活性中心不足及吸附自由能高，钙钛矿氧化物的本征催化活性和稳定性仍然远远达不到实际应用的要求。钙钛矿A和B位点可以容纳具有不同价或半径的多个阳离子，取代A和/或B位点阳离子可以微调物理化学性质。

目前，大多数研究集中在B位点阳离子的改变，因为它们的占据，例如轨道占据通过调制氧相关中间体的结合极大地影响了OER活性。虽然A位并不直接参与催化过程或调节速率控制步骤，但是B位原子的价态和氧空位可能受到A位调节的间接影响。因此，有必要在钙钛矿的A位找到一个理想的调节剂来增强OER活性。
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近日，南开大学杜亚平、沈铸睿和顾超等选择稀土调制的钙钛矿作为载体(Ce-LaCoO3)，用来提高RuO2的OER活性和稳定性。实验结果表明，所制备的RuO2:0.2Ce-LaCoO3催化剂在碱性条件下仅需135 mV的OER过电位就能达到10 mA cm-2的电流密度，Tafel斜率低至64mV dec-1。
此外，RuO2:0.2Ce-LaCoO3在10 mA cm-2下能够连续运行40小时以上，并且在2000次CV循环后，催化剂的电流密度衰减几乎可以忽略不计。同时，XRD和HRTEM证实，稳定性测试后催化剂的结构和形态保持良好。
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一系列表征和理论计算结果显示，载体的调制对提高OER性能有重要作用。对于RuO2:0.2Ce-LaCoO3催化剂，在费米能级附近，Co 3d轨道与Ce 4 f轨道重叠，这大大提高了电子转移效率；同时，Co原子的d带中心与纯LaCoO3相比发生了接近费米能级的偏移，提高了中间体的吸附强度。
Bader电荷结果表明，Ce掺杂导致0.2Ce-LaCoO3中的Co原子失去更多的电子，而引入的Ce获得电子并诱导Ce和Co之间的强电子极化。此外，电子水平较低的Co位点可能有助于在随后的催化过程中更容易转化为活性物种，从而促进OER。综上，该项工作提供了一个合理的方法来设计和定制高活性稀土基钙钛矿催化剂，为推动OER反应的实际应用奠定了基础。
Rare earth-induced CoO6 octahedral distortion in perovskite: an efficient catalytic platform for RuO2-catalyzed water oxidation. Advanced Functional Materials, 2024. DOI: 10.1002/adfm.202411094

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