Revealing the Pseudo-Intercalation Charge Storage Mechanism of MXenes in Acidic Electrolyte
Revealing the Pseudo-Intercalation Charge Storage Mechanism of MXenes in Acidic Electrolyte
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DOI：
10.1002/adfm.201902953
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发表时间：
2019-07-01
影响因子：
19
通讯作者：
Dall'Agnese, Yohan
中科院分区：
文献类型：
--
作者：
Mu, Xinpeng;Wang, Dashuai;Dall'Agnese, Yohan
自从2011年发现Ti3C2Tx以来，二维过渡金属碳化物、碳氮化物和氮化物(统称为MXenes)家族迅速引起了那些开发储能应用的人的注意，例如用于酸性水溶液电解质超级电容器的电极。这些MXenes的优异性能归功于一种伪电容储能机制，该机制基于非矩形的循环伏安曲线和原位X射线吸收光谱检测到的钛氧化态的变化。然而，其伪电容机制还不是很清楚，也没有由于质子插入而引起的尺寸变化的报道。本文采用原位X射线衍射法和密度泛函理论研究了Ti3C2Tx在1m H_2SO_4中的电荷储存机理。结果表明，在0.9V电压窗口内，Ti3C2Tx的c晶格参数发生了0.5埃的膨胀和收缩，表明Ti3C2Tx的电荷存储机制是插层假电容，这为MXene在储能和电化学致动器中的应用提供了可能。
Since the discovery of Ti3C2Tx in 2011, the family of two-dimensional transition metal carbides, carbonitrides, and nitrides (collectively known as MXenes) has quickly attracted the attention of those developing energy storage applications such as electrodes for supercapacitors with acidic aqueous electrolytes. The excellent performance of these MXenes is attributed to a pseudocapacitive energy storage mechanism, based on the non-rectangular shape of cyclic voltammetry curves and changes in the titanium oxidation state detected by in situ X-ray absorption spectroscopy. However, the pseudocapacitive mechanism is not well understood and no dimensional changes due to proton insertion have been reported. In this work, in situ X-ray diffraction and density functional theory are used to investigate the charge storage mechanism of Ti3C2Tx in 1 m H2SO4. Results reveal that a 0.5 angstrom expansion and shrinkage of the c-lattice parameter of Ti3C2Tx occur during cycling in a 0.9 V voltage window, showing that the charge storage mechanism is intercalation pseudocapacitance with implication for MXene use in energy storage and electrochemical actuators.