The role of delaminating agents on the structure, morphology, bonding and electrical properties of HF etched MXenes

Abstract

MXenes (2-dimensional metal carbides and carbonitrides) have gained significant attention as layered materials due to their unique combination of high electrical conductivity and hydrophilic nature. In this study, titanium carbide MXene (Ti₃C₂T_x) nanosheets have been synthesized by etching the MAX phase (Ti₃AlC₂) using hydrofluoric acid (HF) and subsequently delaminated using three different reagents: Tetramethylammonium hydroxide (TMAOH), Dimethyl sulfoxide (DMSO) and Aqueous ammonia (aq. NH₃). The impact of these delaminating agents on the structure, morphology and electrical properties of the resulting MXenes was thoroughly investigated to elucidate the underlying mechanisms. Experimental results reveal that TMAOH is more effective in achieving layer separation than DMSO and aqueous NH₃. Field emission scanning electron microscopy (FESEM) images confirm superior delamination with TMAOH, resulting in thinner, more transparent sheets than those obtained with the other agents. Raman spectroscopy further confirms successful layer separation in samples delaminated with TMAOH and DMSO with various surface functional groups including –OH, –F, and =O present on all delaminated sheets indicating that functionalization occurs during delamination. The electrical conductivity measurements results reveal that the etched MAX phase (MX3) exhibits higher electrical conductivity than the delaminated samples of identical thickness, likely due to the Grotthuss mechanism of proton conductivity playing a dominant role.