Nitrogen-doping engineering in two-dimensional transition-metal carbides for electrochemical hydrogen evolution.

Developing electrocatalysts with the trade-off between overall electrocatalytic performance and economic cost towards hydrogen evolution reaction (HER) is crucial for producing green hydrogen fuels. Although theoretical studies have reported the potential of two-dimensional (2D) MXenes for the HER, their electrocatalytic performance is still unsatisfactory for the particular application due to their low intrinsic active and MXene stacking. To address this problem, we herein modify the electronic structure and increase the interlayer spacing between 2D Ti 3 C 2 T x MXenes through ammonia (NH 3)-assisted hydrothermal approach. The effect of synthesis temperature on the nitrogen doping mechanism and electrochemical behaviors for the HER is systemically explored. As a result, the nitrogen (N)-doped Ti 3 C 2 T x MXene fabricated at 160 °C exhibits the highest HER activity among all 2D N-doped Ti 3 C 2 T x nanosheets with the overpotential/Tafel slope of 186.91 mV RHE /115.94 mV RHE dec−1 in an acidic solution. Due to the synergistic contribution of nitrogen, the N-doped Ti 3 C 2 T x -160 °C has mass activity of 337.95 mA mg−1 at 0.3 V RHE , being 27.50-fold higher than that of pristine Ti 3 C 2 T x. This work indicated that heteroatom doping is a facile but efficient approach for modulating the electronic structure and intrinsic activity of MXene-based materials for electrochemical reactions. [Display omitted] • Nitrogen-doped 2D Ti 3 C 2 T x MXenes are fabricated via a green hydrothermal route. • Effect of treatment temperature on nitrogen doping mechanism and properties of N-doped MXenes is explored. • Relationship between doping nitrogen types and electrochemical behaviors for HER is discussed. • A suitable temperature plays a vital role in optimizing the HER performance of N-doped MXenes. [ABSTRACT FROM AUTHOR]