Effect of glycine functionalization of 2D titanium carbide (MXene) on charge storage

Abstract

Restacking of two-dimensional (2D) flakes reduces the accessibility of electrolyte ions and is a problem in energy storage and other applications. Organic molecules can be used to prevent restacking and keep the interlayer space open. Here, we report on a combined theoretical and experimental investigation of the interaction between 2D titanium carbide (MXene), Ti₃C₂T_x, and glycine. From first principle calculations, we presented the functionalization of glycine on the Ti₃C₂O₂ surface, evidenced by the shared electrons between Ti and N atoms. To experimentally validate our predictions, we synthesized flexible freestanding films of Ti₃C₂T_x/glycine hybrids. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the increased interlayer spacing and possible Ti–N bonding, respectively, which agree with our theoretical predictions. The Ti₃C₂T_x/glycine hybrid films exhibited an improved rate and cycling performances compared to pristine Ti₃C₂T_x, possibly due to better charge percolation within expanded Ti₃C₂T_x.