Photocatalytic hydrogen production using graphitic carbon nitride (GCN): A precise review

The positive feedback mechanism resulting from the exponentially increasing population leads to high energy demands, additional resource utilization, and debilitating nature, making the earth an unsustainable habitat for living. The resulting increase in global temperature, also leads to an increased carbon footprint, creating a chain of events called loop functioning or positive feedback chain. The renewable energy-driven water splitting and generation of hydrogen, which is further used as a clean fuel, serves as a sustainable route for satisfying the over enhanced energy demand and also helps in reducing the global carbon footprint by minimizing the resulting emission. The recent advancement in the photo catalytic systems, especially introduction of advance photocatalysts in the last decade, serves the path more enviably. The photocatalysts involved in the process of hydrogen production and using renewable energy as a driving force, especially solar energy, should remain unaltered. The desired changes in the catalytic activity, separation and conveying of charges at its surface are further catalysed by the solar energy. With technological advancement, novel and cost-effective hydrogen production mechanisms are evolving. This search for a cheaper, effective and sustainable photocatalyst material, which effectively splits the water molecules into desirable hydrogen isotopes is the need of the hour to sustain the ever growing energy demands. And in all this pursuit, a metal-free, suitable bandgap energy, cost-effective and 2D structured compound known as graphitic carbon nitride (GCN or g-C3N4) serves as a potential contender by effective splitting and efficient production of hydrogen. But GCN, even having so much potential, undergoes some challenges such as high density of defects, required surface area and desirable stability that restrict its photocatalytic activity and resulting water splitting efficiency. The present review addresses the latest trends in the composition variabilities in GCN that helps in increased splitting efficiency, doping with metallic particles, heterojunction formation in semiconductors, pore size-perviousity changes, modulation of the bandgap, control of defects and alteration in the surface area. This review also highlights the peak development and changes in the design and morphology of GCN under larger surface area performance and corresponding advancements in hydrogen production. Although not all renewable energy sources are considered; in this review, the photocatalytic production of hydrogen using the solar energy-driven channel is the primary highlight. Further, the concluding portion of this review helps the readers/scientific community to get a clear idea about photocatalytic hydrogen production and its derived routes, which also serve as an inoculum for future studies in the same domain.