Synthesis and characterizations of solid-solution i-MAX phase (W_1/3Mo_1/3R_1/3)₂AlC (R = Gd, Tb, Dy, Ho, Er and Y) and derivated i-MXene with improved electrochemical properties

In this work, a series of new solid-solution i-MAX phase (W_1/3Mo_1/3R_1/3)₂AlC (R = Gd, Tb, Dy, Ho, Er and Y) were synthesized and characterized. From R = Gd to Er, the lanthanide contract is observed while the magnetic behaviors are varied from nonlinear antiferromagnetism-like type for R = Gd to weak ferromagnetism-like one for R = Er with gradually weakened magnetic coupling and reduced Curie-Weiss temperature. The solid-solution i-MXene W_2/3Mo_2/3(R)CT_x was synthesized by selective etching Al and R elements and the highest specific capacitance of 120 Fg⁻¹ at 1 Ag⁻¹ was obtained. By further HM (Hydrazine Monohydrate, N₂H₄•H₂O) treatment and hydrothermal composite with rGO, the specific capacitance is further elevated to 249 Fg⁻¹. This is explained by the increament of O-/N-containing terminals and improved conductivity due to the formation of multidimensional interactive microstructure.