Vapor-Phase Synthesis of Potassium-Doped Polymeric Carbon Nitride Photocatalytic Panels

Potassium-ion (K⁺)-doped polymeric carbon nitride (CN) photocatalyst panels (PCPs) with cyano group defects stand out as an easy, low-cost, and scalable strategy for solar-driven chemical transformations, particularly for hydrogen peroxide (H₂O₂) production via the oxygen reduction reaction (ORR). However, due to the challenges inherent to the synthetic routes, it is almost impossible to grow alkali-metal-doped CN directly on substrates as panels. Here, we introduce a scalable and straightforward vapor-phase condensation and polymerization of CN precursors over KCl-coated substrates, achieving K⁺ doping and forming stable layers with enhanced light absorption, which results in the successful formation of charge carriers below the undoped CN's band edge. The optimal PCPs exhibit improved H₂O₂ production, particularly in 100% ethanol, reaching (3.0 ± 0.4) × 10² mM m^-2 h^-1, ∼18 times higher than control undoped CN PCPs (17 ± 4 mM m^-2 h^-1) in batch mode. The optimized PCP was evaluated as a large-scale panel (ca. 46 cm²) in a continuous-flow configuration for 96 h, yielding ∼39 mM m^{- 2} h^-1 H₂O₂ during the first 24 h and demonstrating this configuration's scalability.