Density functional theory study of active sites on nitrogen-doped graphene for oxygen reduction reaction

Bimetallic CoSn nanoparticles anchored on N-doped carbon as antibacterial oxygen reduction catalysts for microbial fuel cells

Sluggish oxygen reduction reaction (ORR) kinetics and biofilm formation limit the power generation and stability of microbial fuel cells (MFCs). Herein, bimetallic CoSn nanoparticles anchored on ZIF-derived N-doped carbon (CoSn@NC) were designed and synthesized as bifunctional catalysts to accelerate the ORR and improve the antibacterial activity. Sn modulated the electronic structure of bimetallic CoSn by drawing electrons from Co. Electron redistribution of CoSn@NC optimized the O2 adsorption at Co sites for rapid ORR kinetics. The up-shifted d-band center of Co sites reduced the energy barrier of the rate-determining step for *O formation, resulting in efficient catalytic activity. Bimetallic CoSn nanoparticles were beneficial for the four-electron transfer process for more ˙OH species production. Sn2+ and ˙OH synergistically improved the antibacterial activity of CoSn@NC to inhibit the growth of the cathode biofilm and accelerate mass-charge transfer. CoSn@NC demonstrated superior oxygen reduction activity with a half-wave potential of 0.84 V and an onset potential of 0.90 V, respectively. The MFCs assembled with the CoSn@NC cathodic catalyst exhibited an excellent power density of 1380 mW m-2 and long-term stability for 105 h. This work provides a strategy for the design of antibacterial ORR catalysts for improved catalytic activity and long-term stability.

Pyridinic Dominance N-Doped Graphene: A Potential Material for SO2 Gas Detection

The sensors based on graphene have shown great promise in the detection of toxic air pollutants that are detrimental to nature and create risks to human health. Many recent experimental and computational efforts have been dedicated to sensor concepts incorporating pure graphene, graphene oxide, and doped graphene. Herein, a combination of spin-polarized density functional theory (DFT) with van der Waals correction and ab initio molecular dynamics (AIMD) approaches are utilized to assess the gas sensing potential of pyridinic dominance N-doped graphene (PNG) toward SO₂ detection. The potential of PNG systems as SO₂ sensing can be explored through an in-depth analysis of adsorption energies, electronic parameters, charge transfer, selectivity, and thermal stability. It is further demonstrated that external strains and the modulation of external electric fields are two effective ways to modify the adsorption strength. In light of these findings, our studies suggest that PNG monolayers have the potential to be an essential substrate for the detection of SO₂.

Activation of Ibuprofen via Ultrasonic Complexation with Silver in N-Doped Oxidized Graphene Nanoparticles for Microwave Chemotherapy of Cervix Tumor Tissues

An ultrasonic method (20 kHz) is introduced to activate pristine ibuprofen organic molecular crystals via complexation with silver in nitrogen-doped oxidized graphene nanoplatforms (∼50 nm). Ultrasonic complexation occurs in a single-step procedure through the binding of the carboxylic groups with Ag and H-bond formation, involving noncovalent π_C=C → π_C=C* transitions in the altered phenyl ring and π_PY → π_CO* in ibuprofen occurring between the phenyl ring and C-O bonds as a result of interaction with hydroxyl radicals. The ibuprofen-silver complex in ≪NrGO≫ exhibits a ∼42 times higher acceleration rate than free ibuprofen of the charge transfer between hexacyanoferrate and thiosulfate ions. The increased acceleration rate can be caused by electron injection/ejection at the interface of the ≪Ag-NrGO≫ nanoplatform and formation of intermediate species (Fe(CN)₅(CNSO₃)^x- with x = 4 or 5 and AgHS₂O₃) at the excess of produced H⁺ ions. Important for microwave chemotherapy, ibuprofen-silver complexes in the ≪NrGO≫ nanoplatform can produce H⁺ ions at ∼12.5 times higher rate at the applied voltage range from 0.53 to 0.60 V. ≪Ibu-Ag-NrGO≫ NPs develop ∼10⁵ order higher changes of the electric field strength intensity than free ibuprofen in the microwave absorption range of 100-1000 MHz as revealed from the theoretical modeling of a cervix tumor tissue.

Quantum-Chemical Modeling of the Catalytic Activity of Graphene Doped with Metal Phthalocyanines in ORR

The active centers of carbon catalysts doped with cobalt, nickel, copper, manganese, zinc, and chromium were modeled by density functional theory methods. Likewise, the thermodynamics of the oxygen reduction reaction (ORR) on model catalysts were determined. The features of the chemical properties of chromium-containing material, namely its spontaneous oxidation into the hydroxo form, were revealed. In addition, it was established that among the studied catalysts, graphene doped with cobalt showed the best properties.