Sustainable Photocatalytic Hydrogen Generation Using Graphitic Carbon Nitride (g‐C ₃ N ₄ )

ABSTRACT

The growing global energy demand, driven by modern industrialization and transportation, together with the environmental toll of fossil fuel combustion, has intensified the search for clean and sustainable energy alternatives. Hydrogen has emerged as a leading candidate due to its high energy density and zero‐emission combustion profile; however, its conventional production routes, reliant on fossil‐fuel‐based processes such as steam reforming in oil refineries and fertilizer industries remain unsustainable and carbon‐intensive. Photocatalytic water splitting offers a promising alternative, enabling solar‐driven hydrogen generation without secondary pollution. Among photocatalysts explored for this purpose, graphitic carbon nitride (g‐C ₃ N ₄ ) has attracted significant attention owing to its metal‐free composition, visible‐light responsive bandgap, chemical stability, and low‐cost synthesis. This review critically examines recent advances in g‐C ₃ N ₄ ‐based photocatalytic systems for hydrogen evolution, focusing on strategies to overcome its inherent limitations, including rapid charge carrier recombination and limited visible‐light absorption efficiency, through approaches such as heterostructure engineering, doping, morphology control, and cocatalyst integration. The structure–activity relationships governing photocatalytic performance are discussed, along with mechanistic insights into charge separation and transfer. Future research directions are outlined to guide the rational design of efficient, scalable g‐C ₃ N ₄ ‐based photocatalysts for practical solar‐to‐hydrogen energy conversion.