Huan Pang Group: MXene-copper/cobalt hybrids via Lewis acidic molten salts etching

MXenes have attracted great interests as supercapacitors due to their metallic conductivity, high density, and hydrophilic nature. Preparation of MXenes via Lewis acidic molten salts etching was proposed and considered a safer and cleaner process compared to the HF etching. Moreover, surficial -F of MXene could severely thwart ion transport and result in an inferior energy storage capacity which can be avoided in the molten salt strategy.

Prof. Huan Pang and coworkers reported a series of Ti₃C₂-Cu/Co hybrids via molten salt etching to elucidate the existence of Lewis acidic metal elements and their interactions between MXene for the first time. The Cu/Co was demonstrated to partially exist in metallic states as metal particles/clusters in the lamellar structures of MXene with surficial atoms interacted with the Ti₃C₂ via Cu-O and Co-O bonds. The tight interactions between intercalated metal and MXene contribute greatly to the stability of the hybrids during high rate charging/discharging, preventing detachment of the metal clusters. The capacitive contribution of Cu in Ti₃C₂-Cu was extensively illustrated. The avoidance of terminal -F, unique intercalated structure, synergistic interaction between Ti₃C₂ and Cu contribute to the high electrochemical performances as electrode material in supercapacitor. Ti₃C₂-Cu delivered a high specific capacitance of 885.0 F g^-1 at current density of 0.5 A g^-1. Symmetric supercapacitor Ti₃C₂-Cu//Ti₃C₂-Cu was fabricated with a high operating voltage of 1.6 V, areal capacitance of 290.5 mF cm^-2, and 89% long-term stability over 10000 cycles, delivering a high energy density of 103.3 μWh cm^-2 at 0.8 mW cm^-2. The study provided better understanding of molten salts method and new strategies for designing active materials based on MXene-metal hybrids for electrochemical energy storage. This work has been published on Angew. Chem. Int. Ed. (2021, DOI: 10.1002/anie.202112381) entitled with “MXene-copper/cobalt hybrids via Lewis acidic molten salts etching for high performance symmetric supercapacitor”.