Plasmonic metal-modified g-C3N4 photocatalysts for hydrogen evolution: recent advances, mechanisms, and challenges

The transition toward sustainable energy sources has made photocatalytic hydrogen production a compelling prospect for future energy systems. Graphitic carbon nitride (g-C3N4) is a leading photocatalyst due to its visible light response, optimal band positions for water splitting, stability, abundance, and low production cost. However, its practical application is hindered by fast electron–hole recombination, low quantum yield, and limited light absorption. Increasing research indicates that combining plasmonic metals with g-C3N4 can address these issues. Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles like Au, Ag, and Cu, and transition metal nitrides enhances solar absorption, boosts hot electron production, and improves charge carrier separation by forming Schottky junctions and acting as electron sinks. This study summarizes recent advances in the synthesis, design, and function of plasmonic metal-modified g-C3N4 complexes for hydrogen evolution. The authors evaluated synthesis strategies such as in situ growth, ex situ anchoring, alloy formation, and heteroatom doping and their impact on photocatalytic performance. The article emphasizes mechanistic insights, including LSPR-driven charge dynamics and Z-scheme mechanisms, and compares the performance of noble, nonnoble, and nitride-based plasmonic hybrids. It discusses new developments aimed at reducing reliance on noble metals and highlights major challenges such as photo-corrosion, scalability, limited near-infrared (NIR) use, and incomplete understanding of mechanisms, proposing strategies to advance plasmonic g-C3N4 photocatalysts for practical hydrogen production.