Nitrogen-Rich Carbon Dot-Mediated n→π* Electronic Transition in Carbon Nitride for Superior Photocatalytic Hydrogen Peroxide Production

Solar-driven synthesis of hydrogen peroxide (H₂O₂) through photocatalysis stands out as a promising avenue for sustainable energy generation, marked by environmental friendliness and industrial feasibility. However, the inherent limitations of carbon nitride (CN) in photocatalytic H₂O₂ production significantly impede their performance. Herein, a novel 0D/2D carbon dots-modified CN nanosheet heterojunction (CDsMCN) is introduced, synthesized through a hydrothermal-calcination tandem strategy induced by CDs derived from melamine. This innovative technique enhances the n→π* electronic transition in CDsMCN, accelerating the separation efficiency of electron-hole pairs, boosting oxygen adsorption, and promoting a highly selective 2e⁻ ORR. Comparative to pristine CN, CDs₁₀MCN exhibited a remarkable tenfold increase in H₂O₂ production, reaching an impressive 1.48 mmol L⁻¹. Furthermore, CDs₁₀MCN demonstrates exceptional stability, maintaining its catalytic efficiency at the initial level over four consecutive cycles. The notable achievement of a molar selectivity of H₂O₂ ≈80% at an onset potential of 0.6 V (vs RHE) underscores its exceptional ability to produce the desired product selectively. Advanced in situ characterization together with DFT calculations revealed that the ultrathin CDs₁₀MCN nanosheet heterojunction with enhanced n→π* electronic transition improves its optical properties, reduces bandgap, facilitates fast charge migration, and increases photocatalytic H₂O₂ performance, thereby serving as a promising candidate for advanced catalytic applications.