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

Photoinduced charge carrier behavior is critical in determining photoelectrocatalytic activity. In this study, a unique layer-doped metal-free polymeric carbon nitride (C3 N4 ) 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 C3 N4 bottom layer, was formed as a result of the difference in thermal polymerization kinetics associated with the boron-containing H3 BO3 -melamine complex and the phosphorus-containing H3 PO4 -dicyandiamide complex. This layer-doping fabrication strategy effectively contributes to the formation of dual junctions that optimizing charge carrier behavior. The ternary-layer C3 N4 photoanode exhibits significantly enhanced photoelectrochemical water oxidation activity compared to pristine C3 N4 , 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.