Facile synthesis of colloidal nitrogen-doped titanium carbide sheets with enhanced electrochemical performance

Heteroatom nitrogen doping in two-dimensional transition metal carbides, known as MXenes, has been considered as a promising strategy for modulating their electronic structure and electrochemical reactivity. While high-temperature annealing in the presence of a nitrogen source has been one popular method to introduce nitrogen, annealing exfoliated multilayered MXenes typically brings about incomplete delamination and the treatment of delaminated monolayer MXenes often leads to irreversible restacking. Here, starting from the typical carbide precursor, we developed an aqueous colloid containing monolayered nitrogen-doped titanium carbide sheets with excellent dispersity and stability. This achievement is critically dependent on the retaining of the hydrophilic surface of host layers during annealing treatment. The successful realization of nitrogen doping into individual MXene monolayers resulted in enhanced electrical conductivity and redox reactivity, for which the sample exhibited excellent capacitive electrochemical performance (586F/g at a scan rate of 5mV/s) and cycling stability (capacitance retention of 96.2% after 10(4) cycles at 5A/g). This paper presents a feasible and simple strategy for designing nitrogen-doped MXenes colloid, the realization of which promises its facile uses in liquid phase engineering techniques toward versatile applications.