Emerging 2D Non-noble Transition Metal–Group 16 Element Catalysts for High-Performance Solar-Driven Hydrogen Production: A Critical Review

Photocatalytic hydrogen (H₂) production (PHP) is recognized as an advanced method for generating H₂ gas. The efficiency of PHP is mainly governed by the intrinsic nature of photocatalyst properties,. Two-dimensional (2D) photocatalysts, consisting of non-noble transition-metal as cation and group 16 elements as anion (including oxide, sulfide, and selenide), have demonstrated exceptional PHP performance due to their chemical stability, tunable band gaps, and abundance of active sites. Nevertheless, the rapid recombination of photogenerated charge carriers in pristine 2D photocatalysts limits their overall activity. To address this, various modifications have been developed to enhance the activity of PHP, including facet and layered engineering, surface functionalization, doping, defect engineering, metal incorporation, and heterostructure formation. This critical review evaluates up-to-date synthesis strategies, ranging from traditional top-down exfoliations to advanced bottom-up growths, and elucidates how targeted modifications can synergize to overcome persistent efficiency barriers. Mechanistic insights are provided through advanced characterization techniques to detail the behavior of photogenerated charge carriers in enhancing the PHP process. Finally, this review outlines future research and key challenges in developing highly sustainable 2D photocatalytic systems.