Controllable Synthesis of Mesoporous Sulfur-Doped Carbon Nitride Materials for Enhanced Visible Light Photocatalytic Degradation

Abstract

Mesoporous sulfur-doped graphitic carbon nitride (MCNS) materials were successfully synthesized using thiourea as a low-cost precursor and SiO gel solution as a template through a simple thermal condensation method. The effects of three synthesis key factors, namely, the reaction temperature, the reaction time, and the weight ratio of SiO/thiourea, and also their interactions on the removal rate of methyl orange (MO) were investigated using response surface methodology, and the samples were subjected to several characterization techniques. Results showed that the optimized physicochemical properties could be achieved for the MCNS samples by controlling the synthesis key factors, and it was found that the reaction temperature and the reaction time had significant influences on the MO photocatalytic removal. Among bulk graphitic carbon nitride (g-CN), CN (undoped g-CN), CNS (sulfur-doped g-CN without template), and TiO (Degussa P25) samples, the optimized MCNS-4 illustrated the highest photocatalytic activity toward the removal of MO under visible light irradiation. The enhanced performance originated from the synergistic effects of high surface area, mesoporous texture, sulfur doping, and high visible light absorption, which were helpful for the separation and transportation of the photogenerated electron-hole pairs. Furthermore, MCNS-4 revealed high reusability and stability without any significant decrease in its efficiency. Our findings not only confirm the importance of simultaneous sulfur doping and mesoporous structure to synthesize highly active photocatalysts but also might provide a new insight into textural engineering of carbon nitride materials only by the optimization of the synthesis key variables, considering their interactions without relying on extra metal oxides.

Carbon Nitride Materials for Water Splitting Photoelectrochemical Cells

“…Enhanced absorption of CN materials in the visible part of the spectrum has been obtained by the formation of pconjugated polymers incorporating donor-acceptor structures, [101,102] by copolymerization with different organic monomers, [103][104][105] or by incorporation of different heteroatoms [50,[106][107][108] and halogens. [109] Thei ncreased absorbance following the incorporation of iodine [109] and sulfur, [108] for example,i so ne of the reasons behind increased photocurrents.I ng eneral, the E g of CN materials can be easily tuned by changing their C/N ratio or their spatial organization. However,the limited control over the deposition of CN powders onto electrodes hinders the capacity of applying the Figure 3.…”

Recovery Behavior of the Luminescence Peak from Graphitic Carbon Nitride as a Function of the Synthesis Temperature

“…We have found only one paper by Jourshabani et al [31] on the recovery behavior of the PL peak position, which occurred in the synthesis temperature range of 500-584°C. However, in that study SiO 2 nanoparticles were used as templates in the g-C 3 N 4 synthesis procedure, so the direct comparison of our results is complicated.…”

“…We have found only one paper by Jourshabani et al . on the recovery behavior of the PL peak position, which occurred in the synthesis temperature range of 500–584 °C.…”

Influence of nonmetal dopants on charge separation of graphitic carbon nitride by time-dependent density functional theory

“…This finding was inconsistent with the experimental observation that non-metal dopants broadened the visible light absorption range (red shift) of g-C 3 N 4 . [15][16][17][18][19][20][21][22] Moreover, we observed no any charge transfer characteristics on the S0  S1 excited states of the doped HM. These excited states demonstrated strong local excitation characteristics based on their low Δr values (< 2.0 Å).…”