Research Progress of Graphitic Carbon Nitride Composites in Photocatalytic Nitrogen Fixation

As a carbon-free energy carrier with high energy density, ammonia has been extensively utilized across various industrial sectors. However, the conventional Haber-Bosch process for industrial ammonia synthesis faces critical limitations, including harsh operational conditions (high temperature/pressure), excessive energy consumption, and substantial CO₂ emissions, which fundamentally restrict its sustainable development. Photocatalytic nitrogen reduction emerges as a promising alternative strategy, offering advantages of ambient reaction conditions and environmental benignity. Among various photocatalysts, graphitic carbon nitride (g-C₃N₄) has gained significant attention in photocatalytic nitrogen fixation due to its tunable band structure and facile modification characteristics. Nevertheless, pristine g-C₃N₄ suffers from intrinsic limitations, prompting researchers to focus on g-C₃N₄-based composite photocatalysts. This review systematically addresses the current challenges in photocatalytic nitrogen fixation and g-C₃N₄ photocatalysts, followed by a critical analysis of strategies for constructing composite architectures to overcome these limitations. In particular, the merits and drawbacks of different modification approaches were evaluated, while proposing future research directions for g-C₃N₄-based composites in nitrogen photofixation. This comprehensive analysis provides valuable insights and foundational references for advancing photocatalytic nitrogen fixation technologies.