Metal single-atom catalysts (M-SACs) are highly attractive for proton-exchange-membrane water electrolysis (PEMWE), a clean and efficient hydrogen production method. However, in high-density M-SACs, metal atoms tend to aggregate, reducing catalytic activity and durability. Now, researchers from Dongguk University have developed a new synthesis method for M-SACs that prevents the aggregation of metal atoms, significantly improving the hydrogen production performance of PEMWE systems.