DFT Results Research Articles

A novel amidoxime-functionalized covalent organic framework adsorbent for efficient lead ion removal: synthesis and adsorption mechanism

Lead ions are highly toxic heavy metal ions and Pb(Ⅱ) in wastewater threatened seriously human health and environment. Therefore, an effective adsorbent must be developed to remove lead ions from wastewater. In this study, a polycrystalline amidoxime covalent organic framework (DBCC-NHOH) is synthesized by a post-modification method for the elimination of lead (II) from wastewater. The successful preparation of adsorbent (DBCC-NHOH) is demonstrated by the oxygen appearance in SEM-EDS pattern and conversion of -CN to C=N-O and C-N in the FT-IR pattern. DBCC-NHOH is a crystalline porous material and its pore size, specific surface area and pore volume are 3.419nm, 28.154 m2/g and 4.2ⅹ10-8 m3/g respectively. The optimum conditions for the adsorption of Pb(II) by DBCC-NHOH are temperature 298K, time 180min, and pH 5. The maximum adsorption of DBCC-NHOH was 221.37mg/g. Kinetic and thermodynamic investigations indicate that adsorption of Pb(II) by DBCC-NHOH is a monolayer chemisorption and exothermic process. Selectivity experiments indicate that DBCC-NHOH can adsorb Pb(II) efficiently and selectively in complex multi-ion systems. In addition, the adsorption percentage of DBCC-NHOH remained up to 83.20% after five adsorption-desorption experiments. The XPS and FT-IR analyses and DFT results indicated that DBCC-NHOH utilized amidoxime function group to realize the high efficiency of Pb(II) adsorption by electrostatic attraction and chelation.

Photocatalytic degradation of Diuron in water – Impact of Rh impregnation on P25 visible light activity

Significant efforts have lately been dedicated to the development of visible light activated photocatalysts for the degradation of emerging pollutants in water. This study shows the impact of Rh addition on the photocatalytic performance of TiO2 in Diuron degradation through various experimental approaches and modelling. Three samples with different Rh loading (0.5 %, 1 %, and 2 %) were synthesized, characterized, and their activities were evaluated. It was observed that the activity of RhP25 improved under white light irradiation with increasing Rh content. At low Rh loadings the Rh atoms interact with Ti and may be stabilized in the TiO2 lattice. At higher loadings Rh interacts with the O atoms forming two different clusters Rh3O4 and Rh4O6 on the TiO2 surface. This phenomenon was evidenced by DFT, XPS and XRD results. The addition of Rh induce new electronic states in the TiO2 enhancing the visible light absorption. Photocatalytic experiments revealed a threefold increase in Diuron removal under white light irradiation for 2%RhP25 compared to P25, achieving 23 % degradation in comparison with the 7 % observed for the P25 without the Rh addition. Furthermore, repeated experiments did not show significant deterioration of the activity.

A Multipole-Based Reactive Force Field for Hydrocarbons.

The computational complexity of quantum chemistry methods has prompted the development of reactive force fields, facilitating practical applications of molecular dynamics simulations for large-scale reactive systems. Current reactive force fields typically employ intricate corrections based on prior chemical knowledge, which severely impedes their further advancement. This study presents a new atomic multipole-based reactive model with bond free (OPERATOR). The force field is constructed on a simple, physically motivated model within the AMOEBA framework that closely resembles the physical representation of the chemical reaction processes. In the force field, the atomic multipoles are generated dynamically according to the atomic environments, aiming to effectively capture significant changes in the electrostatic environments during chemical reactions. Subsequently, atomic multipole-based charge penetration, polarization, and charge transfer effects are incorporated into the force field to describe the complex electrostatic interactions in the system. The force field also includes van der Waals interactions and three-body potentials. In addition, to extend these nonreactive interactions to chemical reactions, the atom distribution multipole moments are used to characterize different chemical environments. The force field has been optimized using the dataset of potential energy surfaces (PESs) of hydrocarbons derived from DFT results of millions of conformations with six degrees of freedom (DOFs). The results demonstrate that the new force field effectively replicates both the monopoles and the energies. In comparison to ReaxFF, the new force field exhibits comparable or superior performance. Furthermore, molecular dynamics simulations of n-heptane decomposition effectively reproduce the primary products and reactions observed in the experiments. Given the simplicity and physically motivated nature of the model, it is expected that the new force field will be utilized in future studies to investigate chemical reaction mechanisms involving more elements.

Reaction site-isolation for simultaneous removal of NOx and toluene: A reverse strategy to realize bifunctional catalysis

In this study, 3V5W/Cu@Ti catalyst with the function of reaction site-isolation was prepared to achieve the simultaneous removal of NO and toluene. The catalyst was prepared through the hard template and impregnation method, and V-W, and Cu species were introduced into the outer and inner layers of the hollow spherical shell TiO2, respectively. Under the coexistence of multi-pollutants, toluene was completely removed with NO conversions above 90% at 250 ℃. Even at high temperatures of 350-400 ℃, complete conversions of NO and toluene were maintained with apparent lower by-products than those for other catalysts. DFT calculations and activation energy(Ea) indicate that NH3 tends to adsorb and react at the V/W sites on the catalyst's outer layer, while toluene is more likely to adsorb and react at the Cu sites on the inner layer. The Ea and DFT results were well-consistent with the catalytic reactivity, revealing the achievement of reaction site-isolation.

Eu-doped carbon dots-MOF based turn-on fluorescent probe for trace Hg2+ and Pb2+ and construction of the simultaneous detection model

Multiple trace heavy metal pollutants present a serious threat to the aquatic environment, and their coexistence also affected the detection efficiency. This work prepared Eu doped metal organic framework (MOF) complexed with S-containing carbon dots (CD(s)) exhibited dual-emission fluorescence. Its chelation-enhanced fluorescence with heavy metals replaced the original agglomerative fluorescence quenching of pure CD(s), which was utilized to construct a “turn on” fluorescence sensing probe. Based on the XPS, DFT and fluorescence lifetime results, the N, S functional groups on the surface of the materials could bind specifically to Hg2+ and Pb2+ with enhanced sensitivity. The limit of detection reached 76.67 nM for Hg2+ and 5.12 nM for Pb2+ within 2 min detection time. Furthermore, due to the different response mechanism of the two signal peaks to Hg2+ and Pb2+, a three-dimensional data model was developed for simultaneous detection in the co-existence system. The model had been successfully applied to actual Hg2+-Pb2+ containing water samples with recoveries ranged from 93.15 ∼ 105.08 %. The results provided a new strategy for simultaneous detection of trace environmental pollutants.

Comparing the linear and non-linear optical properties of keto-enol forms of N-alkyl, N-aryl, and O-alkyl substituted 2-Hydroxybenzophenone

The Geometrical, electronical, spectral, linear, and non-linear optical properties (NLO) of keto-enol forms of 2-hydroxybenzophenone (2-HBp) derivatives were examined. Ten pairs of 2-HBp derivatives having D-π-A framework with N-alkyl (ethyl, julolidine), N-aryl (phenyl), O-methyl, groups as donor, phenyl ring as aspacer, and carbonyl group linked to phenyl ring consisting of either mono or dicarboxylic acid group as acceptor, were selected. DFT results suggest thatthe keto form is stablein the S0 and S1 states. Further, IR spectra, CV analysis, experimental absorption maxima, and TD-DFT results support the existence of 2-HBp derivatives in keto form. Thermogravimetric analysis shows that 2-HBp derivatives have remarkable thermal stability (∼200 °C), enabling their practical application in NLO. Further, DFT and TD-DFT results show that theketo form of 2-HBp derivatives with lower BLA, higher μ, ω, η, Γ, and hyperpolarizability exhibits superior NLO properties compared to theenol form of 2-HBp derivatives.

Exploring Charge Transfer Mechanisms in Schiff Base‐Modified N‐Doped GQDs: Insights from DFT and Pump‐Probe Spectroscopy for Bioimaging Applications

AbstractIn recent developments, graphene quantum dots (GQDs) have emerged as valuable tools for imaging and biosensing. Various modifications on the GQDs with any desired functionality and attachment of organic molecules and/or nanostructures allow tuning their photophysical properties as well as charge transfer dynamics for bioimaging applications. This study focuses on synthesizing and characterizing of polyethyleneimine‐functionalized nitrogen‐doped GQDs (NC1), Schiff base‐ functionalized nitrogen‐doped GQDs (NC2), and silver nanocomposites of these Schiff base‐functionalized nitrogen‐doped GQDs (NC3). We explore their absorption and emission properties to understand their interactions in the ground state. Furthermore, ultrafast transient absorption spectroscopy measurements reveal that the presence of NC3 shortens the excited state lifetime of NC1 due to charge transfer, resulting in reduced fluorescence intensity. Both experimental and DFT results suggest the potential of NC3 for bioimaging and sensing applications, making them promising candidates for phototheranostic purposes.

Effect of rare earth ions on the optical and electronic properties of defect chalcopyrite: Experimental and theoretical investigation

The present research is a systematic experimental and computational study focused on structural, electronic, and optical properties of ZnGa2S4 doped with neodymium rare earth ions for the first time. High-intensity, narrow-band luminescence peaks are observed in the visible and infrared regions by doping the matrix with Nd ions. These peaks in the background of the broadband spectrum are due to intercenter 4f-4f transitions of Nd3+ ions. The fact that the Raman peaks of the alloy crystal are more intense than that of the pure crystal confirms that the neodymium does not move freely in the lattice and occupies the place of defects. This confirms the results from our X-ray structural analysis. The crystal lattice parameters of the studied materials were determined as follows: a = 5.496 Å, c = 10.99 Å, c/a = 2. To explain the electronic, optical and magnetic properties, using ATK-DFT method, electronic energy band structure, density of states and optical spectrum for pure and doped with ZnGa2S4:Nd compound are computed and discussed. DFT result shows that impurity Nd leads to a decreased bandgap of ZnGa2S4 due to the hybridization of Nd-4d with S-3p orbital in the forbidden gap. The peaks in the optical spectrum are shifted toward the lower energy range for doped supercell.

Constructing 2D Porous ZnO Gas Sensors Based on Polyvinylpyrrolidone-Assisted Zn-MOF Nanosheets for NO2 Detection.

Two-dimensional (2D) ZnO nanomaterials are promising for gas sensing, because of their large surface area, abundant active sites, and rapid charge transfer. However, it is challenging to prepare 2D ZnO nanosheet gas sensors with high sensing performance, due to the tight interlayer stack and low adsorptive property of ZnO for NO2 molecules. Herein, we synthesized Zn-MOF nanosheets employing polyvinylpyrrolidone (PVP) as the structure-directing agent, further through pyrolysis of the Zn-MOF to obtain 2D ZnO nanosheet gas sensors. As anticipated, the 2D ZnO gas sensors exhibited high sensitivity and selectivity for NO2, and the optimal sample could achieve a response value of 162 at the working temperature of 160 °C, which is 10 times higher than that of pristine ZnO. Meanwhile, experimental and DFT results showed that PVP plays critical roles in the lateral lattice growth of 2D Zn-MOF nanosheets, while the existence of PVP makes the ZnO gas sensors with rich porous property and more oxygen vacancy after the pyrolysis process, which promoted the adsorption, activity, and surface reaction for NO2 molecules. It provides a new approach for the application of 2D ZnO nanosheets in the NO2 detection field.

Enhanced carbon monoxide poisoning resistance of Pd/BEA by integrating with CeO2 for low temperature NO adsorption: The role of CeO2 on oxidizing carbon monoxide to CO32−

Passive NOx adsorption (PNA) represents a promising technology for controlling NOx emissions during cold starts. However, Pd/zeolite catalysts, the latest generation of PNA materials, suffer from serious deactivation under CO concentrations, owing to the CO induced aggregation of highly dispersed Pd sites to PdO particles. In this work, we found that the resistance to CO poisoning of Pd/BEA can be enhanced by integrating with CeO2 through physical mixing. The resulting CeO2 + Pd/BEA composite catalyst demonstrated a notably higher NOx storage capacity (with a NOx/Pd ratio of 1.3) compared to Pd/BEA (0.8). This improvement can be attributed to the interaction between CeO2 and the BEA support, which promoted the formation of nitrates on CeO2 during NO adsorption at 80 °C. More importantly, CeO2 effectively shielded Pd2+ ions from reduction by CO, with 88 % of Pd2+ ions remaining after CO exposure, significantly outperforming Pd/BEA, which retained only 66 %. Spectra characterization and DFT results indicate that the defects in CeO2 strongly trapped CO (−0.973 eV), and the oxidation of trapped CO to CO32− by adsorbed oxygen (Oads) was exothermic (−1.35 eV), which reduced the exposure of Pd2+ ions to CO and inhibited the reduction and agglomeration of Pd2+ ions. While the composite sample still exhibited a slight reduction in NOx storage capacity after CO poisoning, with the NOx/Pd ratio decreasing from 1.3 to 0.9. The DFT simulation results indicate that the Ce-Oads bonds in CeO2 are weakened during the decomposition of the CO32− intermediate. This weakening could potentially facilitate the release of Oads, thereby reducing the Oads content as evidenced by spectral evidence. The decrease of Oads diminished nitrate formation on the CeO2 component in composite sample, resulting in the decline of NOx storage capacity after CO poisoning.

Effect of Zn Addition on Phase Evolution in AlCrFeCoNiZn High‐Entropy Alloy

The addition of Zn to AlCrFeCoNi high‐entropy alloy (HEA) poses intriguing questions as to how it would affect phase evolution. Herein, the phase evolution in AlCrFeCoNiZn is studied using a combination of experimental techniques (X‐ray diffraction, scanning electron microscopy, energy‐dispersive spectroscopy, and differential scanning calorimetry) and computational (density‐functional theory [DFT], calculation of phase diagrams, and machine‐learning) methods. Mechanically alloyed and spark‐plasma‐sintered AlCrFeCoNiZn assumes a metastable single‐phase, body‐centered‐cubic (BCC) structure that undergoes diffusion‐controlled phase separation upon subsequent heat treatment to form separate (Al, Cr)‐rich, (Fe, Co)‐rich, and (Zn, Ni)‐rich phases. The formation of (Al, Cr)‐rich phase, not reported previously in AlCrFeCoNi‐based HEAs, is attributed to strong clustering tendency of Cr–Zn and Cr–Ni pairs, combined with the strong ordering of Zn–Ni pair, driving out Cr that in turn combines with Al to form a (Al, Cr)‐rich phase. In the DFT results, the formation of thermodynamically stable L12 phase is shown wherein Cr–Fe–Zn [Al–Ni‐Co] preferably occupy1a (000) [3c (0 ½ ½)] positions. The sluggish diffusional transformation to L12 phase from BCC precursors is attributed to the small stacking‐fault energy of AlCrFeCoNiZn. The equilibrated HEA exhibits a high microhardness of 8.24 GPa with an elastic modulus of 184 GPa.

Electron Sponge Effect by Dynamic-Regulated Electron Self-Flow toward Coupled Electrochemical Ammonia Synthesis.

A dynamic-regulated Pd-Fe-N electrocatalyst was effectively constructed with electron-donating and back-donating effects, which serves as an efficient engineering strategy to optimize the electrocatalytic activity. The designed PdFe3/FeN features a comprehensive electrocatalytic performance toward the nitrogen reduction reaction (NRR, yield rate of 29.94 μg h-1 mgcat-1 and FE of 38.43% at -0.2 V vs RHE) and oxygen evolution reaction (OER, 308 mV at 100 mA cm-2). Combining in situ ATR-FTIR, XAS, and DFT results, the role of the interstitial-N-dopant-induced electron sponge effect has been significantly elucidated in strengthening the electrocatalytic NRR process. Specifically, the introduction of a N dopant, an electron acceptor, initiates the generation of robust Lewis-acidic Fe sites, facilitating free N2 capture and bonding. Simultaneously, after NH3 adsorption, the N dopant can back-donate electrons to Fe sites, strengthening the NH3 deportation through weakening the Lewis acidity of Fe centers. Besides, the electron-deficient Fe sites contribute to the reconstruction of FeOOH, the real active species during the OER, which accelerates the four-electron reaction kinetics. This research offers a perspective on electrocatalyst design, potentially facilitating the evolution of advanced material engineering for efficient electrocatalytic synthesis and energy storage.

Amide/urea-based simple fluorometric receptors for iodide and Hg2+ ions in aqueous medium: Aggregation induced emission and DFT studies

Herein, we report pyrene-tagged amide and urea-based sugar derivatives 1 and 2 in a simple synthetic pathway to recognize I− and Hg2+ ions. Both molecules showed absorbance and fluorescence selectivity towards iodide ions in THF/H2O (7/3, v/v) medium. The selectivity and sensitivity of 2 for iodide ions are superior to 1 due to more H-bond donors in 2. Interestingly, fluorometric receptor 2 exhibited aggregation-induced emission (AIE) at higher pH with a remarkable fluorometric color change. The AIE phenomenon might be explained by the self-association of 2 after forming imine functionality in the alkali medium. The Stern-Volmer plot showed the fluorescence quenching constant of each receptor with an iodide ion and indicated the quenching pathway. The LODs of 1 and 2 for iodide ions were evaluated as 0.84 and 0.17 µM, respectively. The 1:1 binding stoichiometry of 1 or 2 with iodide was found from the Job plot and verified by measuring the complex mass.Further, the complexes of each receptor with I− ions can detect Hg2+ ions selectively by fluorescence turn-on method with low sensitivities (LODs: 0.008 µM for 1 and 0.01 µM for 2). DFT results were used to understand the binding mode of receptors 1 and 2 with iodide ions and the quenching process in the aqueous THF medium. The real application of the receptors was established for the recovery of iodide and Hg2+ ions from natural water samples.

Efficient and selective electroreduction of nitrate to ammonia via interfacial engineering of B-doped Cu nanoneedles

Electrocatalytic nitrate reduction to ammonia is a promising method to mitigate nitrate contamination and produce valuable chemical. However, it still suffers from slow active hydrogen (*H) transfer kinetics and unfavorable thermodynamics. Here the *H transfer and reaction energy barrier of nitrate reduction reaction were regulated on B-doped Cu nanoneedles (Cu NNs-B) to enhance ammonia electrosynthesis via interfacial engineering. The high-curvature nanoneedles showed locally enhanced electric fields, which promoted *H supply from water dissociation. B-doping provided Cu/Cu+ active sites for the activation of nitrate and intermediates. Due to the simultaneously improved *H supply kinetics and reaction thermodynamics, Cu NNs-B was efficient for reducing nitrate to ammonia, achieving high Faradaic efficiencies (FEs) of 95.1-98.6% and ammonia yields of 0.12-1.33mmol·h−1·cm−2 at 50-1500mg·L−1 NO3−-N. Nitrate was selectively converted to ammonia with the remaining nitrate and nitrite concentrations below drinking water standards. Experimental and DFT results revealed Cu NNs-B with properly higher nanotip curvature was more favorable for boosting ammonia electrosynthesis from both kinetics and thermodynamics.

A single-phase Nb25Ti35V5Zr35 refractory high-entropy alloy with excellent strength-ductility synergy

Refractory high entropy alloys (RHEAs) are promising candidates for high-temperature structural materials due to their excellent high-temperature performance. However, the room-temperature brittleness of most alloys results in poor plastic formability, thereby limiting their engineering applications. In this study, Nb25Ti35V5Zr35 alloy with cold-rollability was developed, and its phase stability, tensile mechanical properties, elastic properties, strengthening mechanism, and deformation mechanism were investigated by combining experiments, CALPHAD, DFT and molecular statics (MS) methods. The results demonstrate that Nb25Ti35V5Zr35 alloy possesses good phase stability, with both the as-cast and annealed states maintaining a single-phase BCC structure without undergoing phase transformation. The tensile yield strength of the alloy reaches its peak at 1152 MPa in the cold-rolled condition, while its annealed state exhibits an optimal balance of strength and plasticity, with a yield strength of 836 MPa and an elongation of 22.45 %, respectively. Solid solution strengthening is the primary source of its high strength, with V and Zr playing key roles in this strengthening mechanism. Dislocation slip plays a dominant role in plastic deformation. Additionally, compared to traditional BCC alloys, the significance of edge dislocations in the deformation process is notably enhanced, with the {112} plane serving as the preferred slip plane for dislocations. DFT results indicate that the alloy exhibits significant anisotropy in both Young's modulus and shear modulus. This work contributes to understanding the material properties of the Nb25Ti35V5Zr35 alloy and provides a reference for the design of new ductile RHEAs.

A Strongly Ambiphilic Ferrocene-Based Cyclic (Alkyl)(amino)carbene - Specific Decomposition to an Enamine by a 1,2-Phenyl Shift.

The recently described crystalline cyclic (alkyl)(amino)carbene with a 1,1'-ferrocenylene (fc) backbone fc(CPh2-C-NMes) (A, Mes = mesityl) is highly reactive due to its particularly pronounced ambiphilicity and is thermally not stable in solution due to an intramolecular insertion of the divalent carbon atom into a methyl C-H bond of the Mes substituent. The closely related congener fc(CPh2-C-N-p-C6H4-tBu) (1) cannot undergo such an insertion reaction. Nevertheless, 1 is too short-lived for isolation due to a rapid 1,2-shift of a phenyl group, furnishing the isomeric cyclic enamine fc[C(Ph)=C(Ph)-N-p-C6H4-tBu] (1') in a specific decomposition process unprecedented for CAACs. Trapping of 1 was possible with carbon monoxide, elemental selenium and with [CuBr(SMe2)], respectively affording the aminoketene 1=C=O, the selenoamide 1=Se and the homoleptic CuI complex [Cu(1)2][CuBr2]. 1 is an even stronger ambiphile than A according to NMR spectroscopic data. Similar to A, 1 does not react with H2, because the experimentally observed intramolecular process is kinetically more favourable according to DFT results.

Stable potassium isotope ratios in human blood serum towards biomarker development in Alzheimer's disease.

The Alzheimer's disease (AD)-affected brain purges K with concurrently increasing serum K, suggesting brain-blood K transferal. Here, natural stable K isotope ratios-δ41K-of human serum samples were characterized in an AD biomarker pilot study (plus two paired Li-heparin and potassium ethylenediaminetetraacetic acid [K-EDTA] plasma samples). AD serum was found to have a significantly lower mean δ41K relative to controls. To mechanistically explore this change, novel ab initio calculations (density functional theory) of relative K isotope compositions between hydrated K+ and organically bound K were performed, identifying hydrated K+ as isotopically light (lower δ41K) compared to organically bound K. Taken together with literature, serum δ41K and density functional theory results are consistent with efflux of hydrated K+ from the brain to the bloodstream, manifesting a measurable decrease in serum δ41K. These data introduce serum δ41K for further investigation as a minimally invasive AD biomarker, with cost, scalability, and stability advantages over current techniques.

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Boosting photocatalytic performance of polymeric carbon nitride by adjusting its donor-acceptor structure via functional group modification strategy

Solar-driven photodegradation of pollutant is attractive for environmental remediation. Herein, we designed and synthetized a new kind of group-modified polymeric carbon nitride (PCN) photocatalyst with urea and 4-Nitro-o-phenylenediamine by one-pot method and applied to degrade bisphenol A (BPA) in aqueous solution. The light response range of photocatalyst had been extended a lot due to conjugation and electron-withdrawing properties of nitrobenzene. Physical analysis shows that 4-Nitro-o-phenylenediamine grafting brings an improved charge separation capacity. EPR and DFT results demonstrate the charge separation is significantly affected by the donor-acceptor structure of PCN, which can be altered via aromatic electron-withdrawing group. The kinetic constant of photocatalytic degradation for BPA was promoted by 8.8-times greater than unmodified PCN and a good recyclability was achieved. To verify the universality of group modification strategies, we prepared other two kinds of photocatalysts via electron-withdrawing group modification strategy and their photocatalytic performance all had been improved obviously.

Effect of transition metals (Ni and Co) in the methanol oxidation reaction electrocatalytic activity on Mo2C/MWCNT

The direct methanol fuel cells still recognize Pt and Pd as efficient catalysts for the methanol oxidation reaction (MOR). Our previous study demonstrated the high activity and stability of the Mo2C/MWCNT catalyst for electrocatalytic MOR. To further enhance the performance of Mo2C/MWCNT, the second metals (Ni and Co) are introduced onto Mo2C/MWCNT. It is found that Ni-Mo2C/MWCNT exhibits the highest electrocatalytic MOR activity, with a current density of 192 mA cm−2 in 1 mol/L(M) KOH + 1 M CH3OH electrolyte at 0.6 V (vs. Hg/HgO). Additionally, the stability of Mo2C/MWCNT significantly improves after Ni doping (85.61 % vs. 76.19 %). Characterization results reveal a strong interaction between Ni species and Mo2C, with some Ni ions doping into Mo2C. Furthermore, the Ni-Mo2C nanoparticles are evenly dispersed on MWCNT, with nanoparticle sizes ranging from 5 to 10 nm. DFT results indicate a charge transfer from Mo2C to Ni, resulting in the shift of the d-band center of the surface away from the Fermi level. Moreover, the interface charge transfer resistances of Ni- Mo2C/MWCNT significantly decreased (7.2 vs. 20.0 Ω). As a result, the electrocatalytic MOR activity on Ni- Mo2C/MWCNT improved compared to Mo2C/MWCNT.