Unique Layer‐Doping‐Induced Regulation of Charge Behavior in Metal‐Free Carbon Nitride Photoanodes for Enhanced Performance

Abstract Photoinduced charge carrier behavior is critical in determining photoelectrocatalytic activity. In this study, a unique layer‐doped metal‐free polymeric carbon nitride (C 3 N 4 ) photoanode is fabricated by using one‐pot thermal vapor deposition. With this method, a photoanode consisting of a phosphorus‐doped top layer, boron‐doped middle layer, and pristine C 3 N 4 bottom layer, was formed as a result of the difference in thermal polymerization kinetics associated with the boron‐containing H 3 BO 3 –melamine complex and the phosphorus‐containing H 3 PO 4 –dicyandiamide complex. This layer‐doping fabrication strategy effectively contributes to the formation of dual junctions that optimizing charge carrier behavior. The ternary‐layer C 3 N 4 photoanode exhibits significantly enhanced photoelectrochemical water oxidation activity compared to pristine C 3 N 4 , with a record photocurrent density of 150±10 μA cm −2 at 1.23 V vs. RHE. This layer‐doping strategy provides an effective means for design and fabrication of photoelectrodes for solar water oxidation.