This review summarizes carbon species doping strategies to overcome the photocatalytic limitations of graphitic carbon nitride. Carbon doping is classified into atomic substitution, carbon ring embedding, and external carbon species. Synergistic coupling with heteroatom doping and defect engineering is discussed, emphasizing mechanisms for enhanced light absorption, charge separation, and surface reactivity, and outlining remaining challenges and future perspectives.
ABSTRACT
Photocatalytic technology, as a representative example of chemical reactions driven by solar energy, paves a transformative path toward a sustainable energy future. However, graphitic carbon nitride (g-C3N4, CN), a highly promising metal-free photocatalyst, currently faces practical limitations due to inherent deficiencies in light harvesting, charge transfer, and surface reactivity. Doping modification with carbon species has been demonstrated as an effective strategy to overcome these bottlenecks. This review systematically organizes and precisely classifies carbon species doping strategies into three categories: carbon atom substitution, carbon ring embedding, and external carbon species. Building upon this foundation, this review highlights the synergistic strategies combining carbon species with other modification techniques, such as heteroatom doping, defect engineering, morphology regulation, and heterostructure construction, which elucidate the advantages in overcoming the limitations of single-mode carbon doping and enhancing photocatalytic performance. From an application perspective, we further discuss the critical improvements brought about by carbon-species doping in light absorption, charge transfer, and surface reaction kinetics. Finally, the challenges and future directions for precisely controlling carbon species doping are outlined, which will facilitate the large-scale implementation of g-C3N4-catalyzed energy conversion processes and promote revolutionary and diversified advancements in solar energy utilization.