Tailoring Copper Single‐Atoms‐Stabilized Metastable Transition‐Metal‐Dichalcogenides for Sustainable Hydrogen Production

Unconventional 1T′ phase transition metal dichalcogenides (TMDs) show great potential for hydrogen evolution reaction (HER). However, they are susceptible to transitioning into the stable 2H phase, which reduces their catalytic activity and stability. Herein, we present a scalable approach for designing thermally stable 1T′‐TMDs hollow structures (HSs) by etching Cu1.94S templates from pre‐synthesized Cu1.94S@TMDs heterostructures, including 1T′‐MoS2, MoSe2, WS2, and WSe2 HSs. Furthermore, taking 1T′‐MoS2 HSs as an example, the etched Cu ions can be firmly adsorbed on their surface in the form of single atoms (SAs) through Cu‐S bonds, thereby elevating the phase transition temperature from 149 ºC to 373 ºC. Due to the advantages conferred by the 1T′ phase, hollow structure, and synergistic effect between Cu SAs and 1T′‐MoS2 supports, the fabricated 1T′‐MoS2 HSs demonstrate superior HER performance. Notably, their high‐phase stability enables continuous operation of designed 1T′‐MoS2 HSs for up to 200 hours at an ampere‐level current density without significant activity decay. This work provides a universal method for synthesizing highly stable 1T′‐TMDs electrocatalysts, with a particular focus on the relationship between their phase and catalytic stability.