Surface Redox Pseudocapacitance of Partially Oxidized Titanium Carbide MXene in Water-in-Salt Electrolyte,ACS Energy Letters

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Surface Redox Pseudocapacitance of Partially Oxidized Titanium Carbide MXene in Water-in-Salt Electrolyte
ACS Energy Letters ( IF 19.3 ) Pub Date : 2021-11-24 , DOI: 10.1021/acsenergylett.1c02262
Xuehang Wang _{1,

2} , Seong-Min Bak ₃ , Meikang Han ₁ , Christopher E. Shuck ₁ , Conlan McHugh ₁ , Ke Li ₁ , Jianmin Li ₁ , Jun Tang ₁ , Yury Gogotsi ₁

Affiliation

Achieving pseudocapacitive intercalation in MXenes with neutral aqueous electrolytes and driving reversible redox reactions is scientifically appealing and practically useful. Here, we report that the partial oxidation of MXene intensifies pseudocapacitive Li⁺ intercalation into Ti₃C₂T_x MXene from neutral water-in-salt electrolytes. An in situ X-ray absorption near-edge structure analysis shows that the Ti oxidation state changes during the Li⁺ intercalation, indicating the presence of a surface redox reaction. The Ti oxidation/reduction is further confirmed by an in situ extended X-ray absorption fine structure analysis, which shows a reversible contraction/expansion of the Ti–C interatomic distance. The intensified Li⁺ pseudocapacitive intercalation can be explained by the higher oxidation state of Ti at the open circuit potential. This work demonstrates the possibility of tuning the pseudocapacitive intercalation by adjusting the initial oxidation state of the transition metal on the MXene and offers a facile way to enhance the pseudocapacitance of various MXenes.

中文翻译：

盐包水电解质中部分氧化碳化钛 MXene 的表面氧化还原赝电容

用中性水性电解质在 MXenes 中实现赝电容插层并驱动可逆的氧化还原反应在科学上具有吸引力且实用。在这里，我们报告了 MXene 的部分氧化增强了赝电容 Li ⁺从中性盐包水电解质中嵌入 Ti ₃ C ₂ T _x MXene。原位X 射线吸收近边缘结构分析表明，Ti 氧化态在 Li + 插层过程中发生变化，^表明存在表面氧化还原反应。Ti 氧化/还原通过原位进一步证实扩展的 X 射线吸收精细结构分析，显示了 Ti-C 原子间距离的可逆收缩/膨胀。增强的 Li ⁺赝电容插层可以通过在开路电位下 Ti 的较高氧化态来解释。这项工作证明了通过调整 MXene 上过渡金属的初始氧化态来调整赝电容插层的可能性，并为增强各种 MXene 的赝电容提供了一种简便的方法。

更新日期：2022-01-14

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