Electrochemical Behavior of Ti3C2Tx MXene in Environmentally Friendly Methanesulfonic Acid Electrolyte

Two-dimensional transition metal carbides, nitrides, and carbonitrides, called MXenes, have gained much attention as electrode materials in electrochemical energy storage devices. In particular, Ti3C2Tx has shown outstanding performance in common sulfuric acid (H2SO4) electrolyte. In this work, a more environmentally friendly alternative acidic electrolyte, methanesulfonic acid (MSA), is proposed. The energy storage performance of Ti3C2Tx in aqueous and neat MSA ionic liquid electrolytes is investigated. The specific capacitance of 298 F g(-1) was obtained at a scan rate of 5 mV s(-1) in 4 m MSA and it exhibits excellent cycle stability with retention of nearly 100 % over 10 000 cycles. This electrochemical performance is similar to that of Ti3C2Tx in H2SO4, but using a greener electrolyte. In situ X-ray diffraction analysis reveals the intercalation charge storage mechanism. Specifically, the interlayer spacing changes by up to 2.58 angstrom during cycling, which is the largest reversible volume change observed in MXenes in aqueous electrolytes.