A Strategy of Enhancing the Photoactivity of g-C₃N₄via Doping of Nonmetal Elements: A First-Principles Study

Abstract

An effective structural doping approach has been described to modify the photoelectrochemical properties of g-C 3 N 4 by doping with nonmetal (sulfur or phosphorus) impurities. Here, the substitutional and interstitial doped models of g-C 3 N 4 systems were constructed with different doped sites, and then their dopant formation energies and electronic properties were performed to study the stability and visible-light photoactivity using firstprinciples density functional theory, respectively. Our results have identified that an S atom preferentially substitutes for the edge N atom of g-C 3 N 4 ; however, a P atom preferentially situates the interstitial sites of in-planar of g-C 3 N 4 . Furthermore, it is demonstrated that the doping with nonmetal impurities reduces the energy gap to enhance the visible-light absorption of g-C 3 N 4 . The increased dispersion of the contour distribution of the HOMO and LUMO brought by doping facilitates the enhancement of the carrier mobility, while the noncoplanar HOMO and LUMO favor the separation of photogenerated electron−hole pairs. Especially, P interstitial doping shows a prominent potential due to the appearance of a new channel for carrier migration. It should be pointed out that the proper doping form should be controlled, so that reasonable photoelectrochemical properties can be achieved.

Novel P O codoped g-C3N4 with large specific surface area: Hydrothermal synthesis assisted by dissolution–precipitation process and their visible light activity under anoxic conditions

“…For P O C 3 N 4 , the PL intensity decreases sharply. On the one hand, the calculation results showed that phosphorus doping can increase the dispersion of the contour distribution of HOMO and LUMO, which improves the carrier mobility [23]. The noncoplanar HOMO and LUMO favors the separation of photogenerated electron-hole pairs, decreasing the recombination rate.…”

“…For P O C 3 N 4 , the absorption edge further shifts to 494 nm, corresponding to the band gap energy of 2.51 eV. Ma et al academic calculated the electronic structure of phosphorus doped g-C 3 N 4 using first-principles [23]. They found an isolated P 3p state is localized just 0.15 eV below the bottom of the CB of the host g-C 3 N 4 , leading to the decreased band gap energy.…”

“…For the theoretical investigation, Ma et al investigated the doping effect of sulfur or phosphorus using first-principles study [23]. They suggested that the S atom preferentially substitutes for the edge N atom of g-C 3 N 4 ; however, a P atom preferentially situates the interstitial sites of in-planar of g-C 3 N 4 .…”

g-C3N4-Based Nanomaterials for Visible Light-Driven Photocatalysis

“…g-C 3 N 4 doping is a common strategy to broaden spectral utilization and band alignment to drive separate photogenerated charge carriers. Doping by metals such as Cu and Fe [224][225][226], non-metals such as B, C, O, or S [224,[227][228][229][230][231], and co-doping [232][233][234] have all been employed for environmental depollution applications. For example, S and O co-doped g-C 3 N 4 prepared by melamine polymerization and subsequent H 2 O 2 activation prior to trithiocyanuric acid functionalization (Figure 21a) enhanced the photocatalytic degradation of RhB (Figure 21b) 6-fold relative to the parent g-C 3 N 4 nanosheet [235].…”

Enhanced photocatalytic performance of g-C3N4 nanosheets–BiOBr hybrids

“…However, the catalytic efficiency is quite low due to the high recombination rate of excited charge carriers. As a result, advancement of g-C 3 N 4 structure is extremely desired to avoid this shortcoming and mainly associates with the construction of mesoporous structure [23,24], doping with metal or nonmetal elements [25][26][27][28], composting with other semiconductors [29][30][31][32][33], and exfoliation of bulk form into nanosheets [34][35][36][37]. In particular, the exfoliation of bulk g-C 3 N 4 to nanosheets is able to reduce the edge thickness and create new exposed surface, easily leading to the enlarged specific surface area, enhanced charge carriers motilities through reduced migration distances, and variable conduction and valence band positions, which is favorable to the enhancement of photocatalytic performance [34,36].…”