The increasing concern about environmental pollution and fossil fuel energies have urged researchers to seek renewable energy sources and methods for pollutant decomposition. Photocatalysis seems to be one of the most promising approaches, which uses natural sunlight to produce hydrogen from water and removes organic pollutants from the environment. Among the various photocatalysts, graphitic carbon nitride (g-C3N4) has recently attracted much attention as a metal-free photocatalyst; however, it did not give a satisfactory performance. In this report, hydrogenation and n/n junctions are combined to improve the photocatalytic activities of g-C3N4 nanosheets for both photocatalytic hydrogen generation and the degradation of organic pollutants. The hydrogen evolution activity is enhanced 3.72 times, and the photocatalytic activity in pollution removal is improved 12.38 times from the synergistic effects of hydrogenation and n/n junctions in g-C3N4. Thus, this study may trigger more exciting discoveries in catalyst designs for various photocatalytic renewable energy applications.