Kim Eunji, Kim Seongbeen, Jin Hyeong Min, Kim Gyungtae, Ha Hwi-Heon, Choi Yunhui, Min Kyoungha, Cho Su-Ho, Han Hee, Ahn Chi Won, Roh Jaewoo, Oh Il-Kwon, Lee Jinwoo, Lee Yonghee
Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-Ro, Yuseong-Gu, Daejeon, 34141, Republic of Korea.
National Nano Fab Center (NNFC), 291 Daehak-Ro, Yuseong-Gu, Daejeon, 34141, Republic of Korea.
Nanomicro Lett. 2024 Dec 9;17(1):86. doi: 10.1007/s40820-024-01567-2.
Extensively explored for their distinctive pseudocapacitance characteristics, MXenes, a distinguished group of 2D materials, have led to remarkable achievements, particularly in the realm of energy storage devices. This work presents an innovative Pseudocapacitive Sensor. The key lies in switching the energy storage kinetics from pseudocapacitor to electrical double layer capacitor by employing the change of local pH (-log[H]) in MXene-based flexible supercapacitors during bending. Pseudocapacitive sensing is observed in acidic electrolyte but absent in neutral electrolyte. Applied shearing during bending causes liquid-crystalline MXene sheets to increase in their degree of anisotropic alignment. With blocking of H mobility due to the higher diffusion barrier, local pH increases. The electrochemical energy storage kinetics transits from Faradaic chemical protonation (intercalation) to non-Faradaic physical adsorption. We utilize the phenomenon of capacitance change due to shifting energy storage kinetics for strain sensing purposes. The developed highly sensitive Pseudocapacitive Sensors feature a remarkable gauge factor (GF) of approximately 1200, far surpassing conventional strain sensors (GF: ~ 1 for dielectric-cap sensor). The introduction of the Pseudocapacitive Sensor represents a paradigm shift, expanding the application of pseudocapacitance from being solely confined to energy devices to the realm of multifunctional electronics. This technological leap enriches our understanding of the pseudocapacitance mechanism of MXenes, and will drive innovation in cutting-edge technology areas, including advanced robotics, implantable biomedical devices, and health monitoring systems.
MXenes作为一类独特的二维材料，因其独特的赝电容特性而得到广泛研究，并取得了显著成就，尤其是在储能设备领域。这项工作展示了一种创新的赝电容传感器。关键在于通过在基于MXene的柔性超级电容器弯曲过程中利用局部pH值（-log[H]）的变化，将储能动力学从赝电容器切换到双电层电容器。在酸性电解质中观察到赝电容传感，而在中性电解质中则不存在。弯曲过程中施加的剪切力会使液晶状的MXene片层的各向异性排列程度增加。由于扩散势垒较高，H迁移受阻，局部pH值升高。电化学储能动力学从法拉第化学质子化（嵌入）转变为非法拉第物理吸附。我们利用储能动力学变化引起的电容变化现象进行应变传感。所开发的高灵敏度赝电容传感器具有约1200的显著应变系数（GF），远远超过传统应变传感器（GF：介电电容传感器约为1）。赝电容传感器的引入代表了一种范式转变，将赝电容的应用从仅仅局限于能量设备扩展到多功能电子领域。这一技术飞跃丰富了我们对MXenes赝电容机制的理解，并将推动包括先进机器人技术、可植入生物医学设备和健康监测系统在内的前沿技术领域的创新。
