Simultaneously Improving Inter-Plane Crystallization and Incorporating K Atoms in g-C3N4 Photocatalyst for Highly-Efficient H2O2 Photosynthesis

Abstract

Graphitic carbon nitride (g-C₃N₄) has gained growing attention in hydrogen peroxide (H₂O₂) photosynthesis, but the low activity of two-electron oxygen reduction reaction (2e⁻-ORR) still restricts its photocatalytic H₂O₂-generation performance. Herein, traditional g-C₃N₄ photocatalysts are recrystallized on KI crystal surfaces by a secondary calcination route to synthesize K incorporated highly-crystalline g-C₃N₄ photocatalysts. The synthesized CN-K photocatalyst exhibits improved inter-plane crystallization, narrowed bandgap structure, and smaller particle size from 20 to 50 nm. Moreover, the incorporated K atoms, as excellent catalytic sites, can enhance O₂ adsorption and stabilize the *OOH intermediates, thus improving the 2e⁻-ORR activity of the K incorporated high-crystallization g-C₃N₄ photocatalysts. Consequently, the optimized CN-K(1:6) photocatalyst exhibits a remarkably improved H₂O₂-generation rate of 7.8 mmol·L⁻¹·h⁻¹ with an AQE value of 5.17% at 420 nm, outperforming the traditional g-C₃N₄ sample by a factor of 220. This work uncovers the roles of heteroatoms in promoting the 2e⁻-ORR selectivity of the g-C₃N₄ photocatalyst, and offers novel insights to construct highly-active g-C₃N₄-based materials for H₂O₂ photosynthesis.

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