Engineering MXene-based heterostructures for high-efficiency electrocatalytic water splitting: Advances, mechanisms, and future perspectives

MXene-based materials are an -encouraging new group of 2D electrochemical catalysts that have great promise for use as efficient electrochemical water splitters because they possess high conductivity, hydrophilic surface chemistry, tunable functional terminations, and large electrochemically active surface area. However, pristine MXenes have several limitations, including restacking, surface oxidation and insufficient intrinsic active sites. These limitations can hinder the catalytic efficiency of MXenes and their long lifetime under electrochemical conditions. To overcome these limitations, several significant advances have been achieved in the design and development of heterostructures using MXenes and different materials such as transition metal oxides, sulfides, phosphides, layered double hydroxides, metal-organic frameworks (MOFs) and carbon-based materials. These hybrid materials are capable of facilitating interfacial charge transfer, optimizing the adsorption energies of the intermediates of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), and improving the structural stability of MXenes when subjected to harsh electrochemical tests. In this review, we will provide a mechanism-focused, review-style overview of the progress made in the area of MXene electrocatalysts and the various aspects related to their synthesis, surface and interface engineering, defect modification and heterostructure design. The review will conclude with an appraisal of the key challenges the field currently faces, including oxidation stability, scalable synthesis, reproducibility and industry applicability, as well as a discussion of directions that can be explored in order to create the next generation of MXene-based catalysts that can be utilized for sustainable hydrogen production.