Formation of BNC Coordination to Stabilize the Exposed Active Nitrogen Atoms in g-C₃N₄ for Dramatically Enhanced Photocatalytic Ammonia Synthesis Performance

It is an important issue that exposed active nitrogen atoms (e.g., edge or amino N atoms) in graphitic carbon nitride (g-C₃N₄) could participate in ammonia (NH₃) synthesis during the photocatalytic nitrogen reduction reaction (NRR). Herein, the experimental results in this work demonstrate that the exposed active N atoms in g-C₃N₄ nanosheets can indeed be hydrogenated and contribute to NH₃ synthesis during the visible-light photocatalytic NRR. However, these exposed N atoms can be firmly stabilized through forming BNC coordination by means of B-doping in g-C₃N₄ nanosheets (BCN) with a B-doping content of 13.8 wt%. Moreover, the formed BNC coordination in g-C₃N₄ not only effectively enhances the visible-light harvesting and suppresses the recombination of photogenerated carriers in g-C₃N₄, but also acts as the catalytic active site for N₂ adsorption, activation, and hydrogenation. Consequently, the as-synthesized BCN exhibits high visible-light-driven photocatalytic NRR activity, affording an NH₃ yield rate of 313.9 µmol g⁻¹ h⁻¹, nearly 10 times of that for pristine g-C₃N₄. This work would be helpful for designing and developing high-efficiency metal-free NRR catalysts for visible-light-driven photocatalytic NH₃ synthesis.