Investigation of work function and quantum capacitance of OH-terminated MXenes as supercapacitor electrodes: A theoretical perspective

Abstract

MXene has shown promise in supercapacitor electrodes for energy storage devices. As key parameters to develop new electronic devices, the quantum capacitance and work function (WF) of OH-terminated MXenes with 3d, 4d, d transitional metals are investigated by density functional theory. The most stable configurations of 13 M2C(OH)2 MXenes are found, which are further confirmed by negative formation energies. The low WFs of M2C(OH)2 make them become potential candidates as thermionic electron emitters, especially for Sc2C(OH)2 and Lu2C(OH)2 with extra low WFs. Sc2C(OH)2, Cr2C(OH)2, Y2C(OH)2, and Lu2C(OH)2 are considered as negative electrodes, Other nine systems are potential positive electrodes for larger |Qp|/|Qn| than 1, especially for V2C(OH)2, Nb2C(OH)2, and Mo2C(OH)2. Th wide voltage maintains the electrode types of all systems unchanged, but drastically increases the |Qp|/|Qn| of V2C(OH)2. The quantum capacitance of M2CT2 with different terminations is further explored.