Phenothiazine–MXene Aqueous Asymmetric Pseudocapacitors

We report here a molecular phenothiazine-based electrode as a high capacitance and long cycle life (77% retention after 80 000 cycles) pseudocapacitive organic material after hydrothermal deposition on reduced graphene oxide (rGO). Given the high stability of phenothiazine coated rGO hybrid electrodes under positive potentials, pseudocapacitive asymmetric supercapacitors were manufactured using two-dimensional titanium carbide (Ti3C2Tx) MXene as the negative electrode, which allowed expansion of the voltage window up to 1.4 V in 3 M H2SO4. The optimized asymmetric pseudocapacitors showed capacitance retention of over 80% after 30 000 cycles at 100 mV/s, which is one of the highest for aqueous asymmetric supercapacitors.