Unique layer‐doping‐induced regulation of charge behavior in metal‐free carbon nitride photoanodes for enhanced performance

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Photoinduced charge carrier behavior is critical in determining photoelectrocatalytic activity. In this study, a unique layer-doped metal-free polymeric carbon nitride (C3N4) 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 C3N4 bottom layer, was formed as a result of the difference in thermal polymerization kinetics associated with the boron-containing H3BO3–melamine complex and the phosphorus-containing H3PO4–dicyandiamide complex. This layer-doping fabrication strategy effectively contributes to the formation of dual junctions that optimizing charge carrier behavior. The ternary-layer C3N4 photoanode exhibits significantly enhanced photoelectrochemical water oxidation activity compared to pristine C3N4, 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.