Electronic Structure Engineering of Carbon Nitride Materials by Using Polycyclic Aromatic Hydrocarbons

Abstract

The design of charge separation sites under illumination in semiconductors is as tanding challenge for their utilization as photo(electro)catalysts. Here, the synthesis of modified carbonn itride materials (CNs) with donor-acceptor (D-A) domains, with altering electronic structure, is reported. To do so, new monomersb ased on polycyclic aromatic hydrocarbons (PAH)-substituted 1,3,5-triazine wered esigned, which were then embedded within cyanurica cid-melamine supramolecular assemblies to form CN precursors. The conjugation degree of PAHs was systematicallyc hanged, from single benzene ring up to pyrene unit, elucidating the role of the conjugation degree on the morphology, structure and electronic properties as well as photo(electro)catalytic activity.T he careful design of the D-A sites results in excellent photocatalytic activity as well as long-term stability for the hydrogen evolution reaction. Moreover,P AH-CNs films exhibit enhanced charges eparation, optical absorption, electrochemical surface area and electronic conductivity,l eading to an outstanding photoelectrochemical( PEC) activity compared to pristine CN.[a] Dr.Scheme1.Carbon nitride (CM and CMR-CN)synthesis at 550 8Cf rom hydrogen-bonded supramolecular complexes as startingr eactants. Figure 1. SEM images of CMR supramolecular complexes prepared in water.

Electrophoretic deposition of antimonene for photoelectrochemical applications

“…The deposition of Sb flakes on TiO2 dramatically enhances the photoanodic performance, reaching an initial current of more than 250 µA cm -2 (vs 20 µA cm -2 of bare TiO2 electrodes) in a basic media, 130 µA cm -2 in acidic electrolyte, and 100 µA cm -2 in neutral pH (Figure 4a, b). We want to note that, despite higher values have been reported in the state of the art of photoelectrochemical cells using materials such like perovskites, [47] bismuth vanadates (BiVO4), [48,49] metal oxides, [50,51] carbon nitrides (C3N4) [52,53] and more (Table S1), [54][55][56][57] the value reported here is considerably high for TiO2-based catalysts. Additionally, up to our knowledge this is the first time that antimonene is utilized in a photo-electrochemical cell and furthermore showing such a marked enhancement.…”

Boosting Photocatalytic Activity Using Carbon Nitride Based 2D/2D van der Waals Heterojunctions

“…The introduction of the graphene sheet in the g-C 3 N 4 /PDI scaffold in the 2D/2D assembly was found to again boost the H 2 O 2 generation rate. 707 Additionally, some other approaches such as the introduction of donor−acceptor assemblies, 708 polyaromatic units, 709,710 increasing π conjugation, addition N and C rich units, etc. have also been used to reduce recombination on the sheets.…”

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

“…13−15 A significant improvement in the e − diffusion toward the conductive substrate can be achieved by the introduction of an e − acceptor layer (e.g., TiO 2 , reduced graphene oxide) 16,17 and/or by doping the CN with C−C bonds. 18,19 The latter alters the electronic conductivity within the CN, thanks to the increase in the number of delocalized electrons within its framework. Longer e − diffusion length allows in turn a better light harvesting thanks to the use of a thicker absorber layer.…”

“…Recently, polymeric carbon nitrides (CNs) have emerged as new and promising SCs for PECs, owing to their tunable band gap, suitable energy bands, high stability, and low cost. , However, despite their advantages and proven performance, to date, progress on CNs’ utilization as PEC photoanodes has been limited by the poor charge separation and fast recombination under illumination. In the last years, we and others proposed several methods to increase charge separation and electron (e – ) mobility within the CN layer and hole (h + ) extraction to the solution. − The enhancement of charge separation under illumination can be obtained by the formation of a new electronic configuration, for example, from heterojunctions or defects, − or by facilitating the transfer of e – –h + pairs to another medium (to another SC layer, a catalyst, or the solution). − A significant improvement in the e – diffusion toward the conductive substrate can be achieved by the introduction of an e – acceptor layer (e.g., TiO 2 , reduced graphene oxide) , and/or by doping the CN with C–C bonds. , The latter alters the electronic conductivity within the CN, thanks to the increase in the number of delocalized electrons within its framework. Longer e – diffusion length allows in turn a better light harvesting thanks to the use of a thicker absorber layer.…”