Carbon Nitride Materials for Photocatalytic Applications

Carbon nitride materials, notably graphitic carbon nitride (g-C3N4) and related heptazine-based polymers often referred to as “melon”, have emerged as versatile photocatalysts for solar-driven hydrogen evolution, pollutant degradation and small-molecule activation. Their layered, metal-free frameworks comprise conjugated tri-s-triazine or heptazine units linked by sp2-bonded nitrogen, yielding suitable bandgaps (~2.6 eV) for visible-light absorption. These materials combine low cost, chemical robustness and tunable electronic properties. However, their practical performance has been constrained by modest light harvesting, rapid electron–hole recombination and limited surface active sites. Recent strategies to overcome these barriers include defect engineering, heterostructure formation, co-catalyst integration and bandgap modulation through compositional or morphological control. Collectively, these approaches aim to enhance charge separation, extend absorption into the visible region and promote surface redox reactions, advancing carbon nitride photocatalysts towards scalable solar-fuel production and environmental remediation.

Research from Nature Portfolio

Recent studies have identified specific molecular defects and dynamic photochemical processes that underpin enhanced activity. One investigation pinpointed cyanamide groups as catalytically relevant “defects” within heptazine-based polymers, revealing that rational insertion of these moieties can raise hydrogen evolution rates by more than an order of magnitude and boost apparent quantum efficiency. Computational modelling showed that cyanamide sites improve coordination to platinum co-catalysts and facilitate charge separation. Another report has focused on carbon-dot hybrids, demonstrating that incorporation of a photobase unit accelerates proton abstraction from water upon light excitation. Ultrafast spectroscopy established proton transfer within tens of picoseconds, linking the photobasic effect to elevated hydrogen generation. Together, these works provide a mechanistic framework for bespoke design of high-performance carbon nitride photocatalysts.

Carbon Nitride Materials for Photocatalytic Applications publication trend

The graph below shows the total number of articles in carbon nitride materials for photocatalytic applications across all publications each year (not limited to Nature Index journals).

Technical terms

Graphitic carbon nitride (g-C3N4): Metal-free polymeric semiconductor built from tri-s-triazine or heptazine units linked by sp2-bonded nitrogen.

Heptazine (“melon”): Polymeric carbon nitride composed of fused heptazine rings forming a layered two-dimensional structure.

Apparent quantum efficiency: Ratio of number of charge carriers contributing to a photocatalytic reaction to the number of incident photons.

Photobasic effect: Light-induced increase in basicity that facilitates proton abstraction from water upon excitation.

Defect engineering: Introduction or manipulation of chemical or structural irregularities to improve charge separation and catalytic site activity.

Type-II band alignment: Heterostructure arrangement where conduction and valence band edges of two materials favour spatial separation of electrons and holes.

References

1. Rational design of carbon nitride photocatalysts by identification of cyanamide defects as catalytically relevant sites. Nature Communications (2016).
2. Photobase effect for just-in-time delivery in photocatalytic hydrogen generation. Nature Communications (2020).
3. Bandgap Engineering of Melon using Highly Reduced Graphene Oxide for Enhanced Photoelectrochemical Hydrogen Evolution. Advanced Materials (2023).
4. First-Principles Calculations of Exciton Radiative Lifetimes in Monolayer Graphitic Carbon Nitride Nanosheets: Implications for Photocatalysis. ACS Applied Nano Materials (2021).
5. Influence of High Temperature Synthesis on the Structure of Graphitic Carbon Nitride and Its Hydrogen Generation Ability. Materials (2020).