S-doped multilayer niobium carbide (Nb4C3Tx) electrocatalyst for efficient hydrogen evolution in alkaline solutions

Developing highly efficient and low cost electrocatalysts for hydrogen evolution reaction (HER) is a popular topic for electrocatalytic water splitting to hydrogen technology. Herein, we report a novel heterostructure electrocatalyst prepared by the S-doping multilayer niobium carbide (S-ML-Nb4C3Tx) through hydrothermal technique. Compared with pristine ML-Nb4C3Tx catalyst, the as prepared electrocatalyst presents remarkable catalytic activity for HER with lower overpotential of 118 mV@10 mA/cm2 and a Tafel slope of 104 mV dec−1 in 1.0 M KOH solution. In addition, the catalyst exhibits a stable electrochemical durability of as long as 24 h in 1.0 M KOH. Efficient HER ability of the S-ML-Nb4C3Tx catalyst is mainly attributed to the following points: Firstly, the ML-Nb4C3Tx with superior conductivity and stability can effectively avoid the aggregation and oxidation. Secondly, the conversion of fluorine termination groups to –OH by TMAOH treatment can expose more active sites. Further, after the S-doping by hydrothermal reaction, NbS2 nanoparticles can prevent the ML-Nb4C3Tx nanosheets from restacking. As a result, the enlarged interlayer spacing and porous structure of the catalyst are conducive to the charge transfer. In addition, the introduction of NbS2 nanoparticles on the surface of ML-Nb4C3Tx can form heterostructure and subsequently adjust the electronic structure of the catalyst, accelerate the electron transfer, and improve the HER performance. This work presents a new strategy for the designing and preparation of low cost MXene-based catalysts for HER application.