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 (H 2 O 2 ) 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 H 2 O 2 production, particularly in 100% ethanol, reaching (3.0 ± 0.4) × 10 2 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 cm 2 ) in a continuous‐flow configuration for 96 h, yielding ∼39 mM m − 2 h −1 H 2 O 2 during the first 24 h and demonstrating this configuration's scalability.