MXene-Copper/Cobalt Hybrids via Lewis Acidic Molten Salts Etching for High Performance Symmetric Supercapacitors

MXenes have attracted great interests as supercapacitors due to their metallic conductivity, high density, and hydrophilic nature. Herein we report Ti₃ C₂ -Cu/Co hybrids via molten salt etching in which the existence of metal atoms and their interactions with MXene via surficial O atoms were elucidated by XAFS for the first time. The electrochemical investigation of Ti₃ C₂ -Cu electrode demonstrated the pseudocapacitive contribution of Cu and a splendid specific capacitance of 885.0 F g^-1 at 0.5 A g^-1 in 1.0 M H₂ SO₄ . Symmetric supercapacitor Ti₃ C₂ -Cu//Ti₃ C₂ -Cu was demonstrated with operating voltage of 1.6 V, areal capacitance of 290.5 mF cm^-2 at 1 mA cm^-2 , and stability over 10 000 cycles. It delivered an areal energy density of 103.3 μWh cm^-2 at power density of 0.8 mW cm^-2 , based on which a supercapacitor pouch was fabricated. It provides deeper insights into the molten salt mechanism and strategies for designing MXene-based materials for electrochemical energy storage.