Hydrogen energy is vital for achieving carbon neutrality, and the article discusses innovative methods to produce hydrogen efficiently. The focus is on photocatalytic water splitting using graphitic carbon nitride (g-C3N4) with Mo doping. This approach enhances the photocatalytic activity by providing active sites for water decomposition. The article emphasizes the significance of single-atom catalysis and the use of transition metals like Mo to improve catalytic efficiency. Strategies such as defect engineering, doping, and morphological control are explored to enhance carrier mobility and stabilize Mo single-atom loading. The synthesis process involves introducing S atoms to optimize the carrier surface, resulting in a new Mo single-atom configuration with improved hydrogen evolution performance. Detailed characterization techniques confirm the unique structure of the catalyst. Overall, the study presents promising advancements in photocatalytic hydrogen evolution, paving the way for sustainable energy production.