Heteroatom-doped MXenes as electrocatalysts for hydrogen evolution reaction: A review on the recent advances, mechanisms and prospects

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have emerged as a promising class of electrocatalyst materials for the hydrogen evolution reaction (HER) due to their unique properties. These include metallic conductivity imparted by transition metals (TMs) in their structure and terminations, offering tunable surface chemistry. While initial studies revealed low overpotentials for HER using pristine MXenes, their electrocatalytic performance remains limited by the kinetics of hydrogen (H2) adsorption/desorption steps. Recently, heteroatom doping has been explored as an effective approach to optimize the surface and electronic properties of MXenes aimed at enhancing HER kinetics. This review aims to systematically analyze doping mechanisms in MXenes from three perspectives - how lattice modifications, functional group substitutions, and interface alterations influence electrocatalytic activity. The review also critically examines challenges hindering doped MXene effectiveness and outlines promising future research avenues. These include developing synthetic methods enabling precise control over dopant introduction and investigating dopant-driven modifications correlated to HER activity. Overall, gaining fundamental insights into heteroatom doping mechanisms can direct the rational design of high-performance MXene-based HER electrocatalysts. Addressing existing limitations may help harness their full potential for clean H2 generation applications.