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 (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.

Semiconducting Polymers for Oxygen Evolution Reaction under Light Illumination

“…Thermal vapor deposition was demonstrated as a typical approach to form a multilayered PCN photoanode, namely, a PB−PCN photoanode. 448 In this work, a P-PCN layer, a B-PCN layer, and a pristine M-PCN layer were realized on the top, middle, and bottom positions of the multilayered photoanode, respectively, by thermal condensation of the mixed precursors, namely, a Bcontaining H 3 BO 3 −melamine complex and a P-containing H 3 PO 4 −DCDA complex. The formation of the distinct order of the photocatalytic layer can be attributed to the different thermodynamics and kinetics associated with precursor polymerization, as shown in Figure 30a.…”

Highly Efficient Polymeric Carbon Nitride Photoanode with Excellent Electron Diffusion Length and Hole Extraction Properties

“…Recently, it was demonstrated that charge transfer and h + extraction properties in CN-PEC are correlated to the order within the CN. [22,23] In the case of a better stacking order of the graphitic layers, a hole extraction efficiency of ~47% was obtained. [24] However, in all the abovementioned scenarios, only one problem was tackled either ediffusion or h + extraction due to synthetic limitations.…”

“…In the presence of hole scavengers as triethanolamine or redox electrolytes (e.g., polysulfide), , h + extraction efficiencies can be dramatically increased, owing to the fast e – –h + transfer. Recently, it was demonstrated that charge transfer and h + extraction properties in CN-PEC are correlated to the order within the CN. , In the case of a better stacking order of the graphitic layers, a hole extraction efficiency of ∼47% was obtained . However, in all of the above-mentioned scenarios, only one problem was tackled, either e – diffusion or h + extraction due to synthetic limitations.…”

Recent Progress on Photoelectrochemical Water Splitting of Graphitic Carbon Nitride (g−CN) Electrodes

“…The photocurrent density of K&I co-doped g−CN is approximately 50.3 μA cm −2 at 0.5 V versus Ag/AgCl. Luan et al [ 122 ] reported a unique multi-layer doped non-metal g−CN photoanode using a one-pot TVC. In this structure, a P-doped top layer, B-doped middle layer, and pure g−CN bottom layer were designed to enhance the photocurrent density by nearly nine times that of the pure g−CN.…”

“…Reprinted with permission from ref. [ 122 ] Copyright 2020 Wiley−VCH. ( f ) A diagram illustrating the fabrication of FTO/TiO 2 −nanorod/P−g−CN/metal phosphide electrodes for the PEC water splitting and ( g ) the Tauc plots.…”