Materials design of edge-modified polymeric carbon nitride nanoribbons for the photocatalytic CO2 reduction reaction

Nanoribbon construction and modification with functional groups are important methods to improve the performance of photocatalysts. In this paper, density functional theory (DFT) calculations are applied to assess the electron absorption capacity of different model structures in the photocatalytic CO₂ reduction reaction (CO₂RR), i.e., melon-based carbon nitride nanoribbons (MNRs) and edge-modified melon-based carbon nitride nanoribbons (X-MNRs, X = NO₂, CF₃, CN, CHO, F, Cl, CCH, OH, SH, CH₃, and H). It is found that X-MNRs (X = NO₂, CN, CHO, CCH, OH, and H) have a significantly reduced band gap. Meanwhile, the VBM and CBM are effectively separated with the same optical absorption wavelength range, agreeing with the experimental observations. More importantly, the Gibbs free energy difference of the CO₂RR rate-determining step is greatly reduced in MNRs, CHO-MNRs, CN-MNRs etc. with the formation of CO or HCOOH. The mechanism investigation indicates that the materials design via edge-group modification can optimize the CO₂RR process.

Synthesis and characterization of CuO@S-doped g-C3N4 based nanocomposites for binder-free sensor applications

This study presents the simultaneous exfoliation and modification of heterostructured copper oxide incorporated sulfur doped graphitic carbon nitride (CuO@S-doped g-C₃N₄) nanocomposites (NCs) synthesized via chemical precipitation and pyrolysis techniques. The results revealed that the approach is feasible and highly efficient in producing 2-dimensional CuO@S-doped g-C₃N₄ NCs. The findings also showed a promising technique for enhancing the optical and electrical properties of bulk g-C₃N₄ by combining CuO nanoparticles (NPs) with S-doped g-C₃N₄. The crystallite and the average size of the NCs were validated using X-ray diffraction (XRD) studies. Incorporation of the cubical structured CuO on flower shaped S-doped-g-C₃N₄ was visualized and characterized through XRD, HR-SEM/EDS/SED, FT-IR, BET, UV-Vis/DRS, PL, XPS and impedance spectroscopy. The agglomerated NCs had various pore sizes, shapes and nanosized crystals, while being photo-active in the UV-vis range. The synergistic effect of CuO and S-doped g-C₃N₄ as co-modifiers greatly facilitates the electron transfer process between the electrolyte and the bare glassy carbon electrode. Specific surface areas of the NCs clearly revealed modification of bulk S-doped g-C₃N₄ when CuO NPs are incorporated with S-doped g-C₃N₄, providing a suitable environment for the binder-free decorated electrode with sensing behavior for hazardous pollutants. This was tested for the preparation of a 4-nitrophenol sensor.

Photocatalytic Degradation of Fluoroquinolone Antibiotics in Solution by Au@ZnO-rGO-gC3N4 Composites

The photocatalytic degradation of two quinolone-type antibiotics (ciprofloxacin and levofloxacin) in aqueous solution was studied, using catalysts based on ZnO nanoparticles, which were synthesized by a thermal procedure. The efficiency of ZnO was subsequently optimized by incorporating different co-catalysts of gC3N4, reduced graphene oxide, and nanoparticles of gold. The catalysts were fully characterized by electron microscopy (TEM and SEM), XPS, XRD, Raman, and BET surface area. The most efficient catalyst was 10%Au@ZnONPs-3%rGO-3%gC3N4, obtaining degradations of both pollutants above 96%. This catalyst has the largest specific area, and its activity was related to a synergistic effect, involving factors such as the surface of the material and the ability to absorb radiation in the visible region, mainly produced by the incorporation of rGO and gC3N4 in the semiconductor. The use of different scavengers during the catalytic process, was used to establish the possible photodegradation mechanism of both antibiotics.