Two-dimensional titanium carbonitride MXene as a highly efficient electrocatalyst for hydrogen evolution reaction

In this paper, we report, for the first time, on the electrochemical catalytic activity of 2D titanium carbonitride MXene for hydrogen evolution reaction (HER). According to our study, 2D titanium carbonitride exhibited much higher electrocatalytic activity than its carbide analogues, achieving an onset overpotential of 53 ​mV and Tafel slope of 86 ​mV dec⁻¹, superior to the titanium carbide with onset overpotential of 649 ​mV and Tafel slope of 303 ​mV dec⁻¹. The obtained onset overpotential for 2D titanium carbonitride is lower than those of all the reported transition metal carbides MXene catalysts without additives, so far. Density functional theory calculations were conducted to further understand the electrochemical performance. The calculation results show that a greater number of occupied states are active for Ti₃CNO₂, revealing free energy for the adsorption of atomic hydrogen closer to 0 than that of Ti₃C₂O₂. Both experimental and calculation studies demonstrate the excellent electrocatalytic behavior of titanium carbonitride. The investigation of 2D titanium carbonitride opens up a promising paradigm for the conscious design of high-performance non-precious metal catalyst for hydrogen generation.