Rational design of interface-coupled Nb-doped MoSe2/Nb2CTx MXene heterostructures with enriched active sites toward enhanced hydrogen evolution reaction

Hydrogen (H 2 ) is a clean fuel with the potential to enable carbon-neutral energy systems. However, its large-scale application requires low-cost, efficient, and durable electrocatalysts for the hydrogen evolution reaction. Herein, we report a heterostructure consisting of niobium-doped molybdenum diselenide (Nb-MoSe 2 ) anchored on Nb 2 CT x MXene. Nb-MoSe 2 was synthesized via a hydrothermal route, while Nb 2 CT x was prepared through selective acid etching of Nb 2 AlC MAX phase. The heterostructure was assembled using a simple ultrasonication process. Nb-doping modifies the electronic environment of MoSe 2 and increases the density of catalytically active sites, while the Nb 2 CT x MXene provides a highly conductive scaffold to prevent particle agglomeration and facilitate rapid charge transfer. Electrochemical testing in acidic media reveals that the optimized Nb-MoSe 2 /Nb 2 CT x exhibits improved HER performance, achieving an overpotential of 287 mV at 10 mA cm −2 and 405 mV at 50 mA cm −2 , with a Tafel slope of 122 mV dec −1 and stable operation over 48 h using a carbon cloth substrate. Compared to Nb-MoSe 2 , Nb 2 CT x and MoSe 2 , the heterostructure shows enhanced catalytic activity, which is associated with the combined contribution of Nb-doped MoSe 2 and the conductive MXene support. This study offers a scalable approach to designing heterostructure electrocatalysts through doping and surface design for hydrogen technologies. • Nb-MoSe 2 /Nb 2 CT x formed by hydrothermal, etching and sonication strategies. • Nb doping tunes the electronic structure of MoSe 2 , enhancing its conductivity and active sites. • Conductive Nb 2 CT x MXene ensures fast charge transfer, high conductivity, and stability. • Delivers 287 mV at 10 mA cm −2 and 405 mV at 50 mA cm −2 with efficient HER activity. • Nb-MoSe 2 /Nb 2 CT x demonstrates good operational stability over 48 h in acid media.