Theoretical study on the morphology of cobalt nanoparticles modulated by alkali metal promoters

Cobalt nanoparticles(NPs)catalysts are extensively used in heterogeneous catalytic reactions,and the addition of alkali metal promoters is a common method to modulate the catalytic performance because the catalyst's surface structures and morphologies are sensitive to the addition of promoters.However,the underlying modulation trend remains unclear.Herein,the adsorption of alkali metal promoters(Na and K)on the surfaces of face-centered-cubic(FCC)and hexagonal-closest packed(HCP)polymorphous cobalt was systematically investigated using density functional theory.Furthermore,the effect of alkali promoters on surface energies and nanoparticle morphologies was revealed on the basis of Wulff theory.For FCC-Co,the exposed area of the(111)facet in the nanoparticle increases with the adsorption coverage of alkali metal oxide.Meanwhile,the(311),(110),and(100)facets would disappear under the higher adsorption coverage of alkali metals.For HCPCo,the Wulff morphology is dominated by the(0001)and(1011)facets and is independent of the alkali metal adsorption coverage.This work provides insights into morphology modulation by alkali metal promoters for the rational design and synthesis of cobalt-based nanomaterials with desired facets and morphologies.

Theoretical Study on the Structural and Optoelectronic Properties of the Linear Perfluorooctane Sulfonate (PFOS)

The perfluoroalkyl substances（PFS） have attracted considerable attention in recent years as a persistent global pollutant to be able to bioaccumulate in higher organisms.In this paper,theoretical analysis on electronic structures,optoelectronic properties and absorption spectra properties of the perflurooctane sulfonate（PFOS） in gas phase have been investigated by using the DFT/TD-DFT method.The geometric structures,electrostatic potentials,energy gaps,ionization potentials,electron affinities,frontier molecular orbital,excitation energies and absorption spectra for the ground state of PFOS were calculated.The result indicates that the ability of accepting electron of neutral PFOS is larger than that of anionic PFOS,while the electron excited by UV irradiation from HOMO to LUMO in the anionic PFOS is easier than that in the neutral PFOS.

DFT Study of Charge Effect on the Odd-even Oscillatory Behavior in Stabilities for Gold Clusters

The comparative study of charge effect on the size-dependence stabilities of gold clusters Aun^z （n = 2-12, z = 0/±1） in gas phase is performed at the M06-L/Lanl2dz level. The lowest-energy structures charged by -1, 0 and ＋1 are optimized. The result shows that the geo- metries of the clusters with over 7 atoms tend to be cake-like. From the two- to three-dimensional geometries, the oscillatory behaviors are exhibited in the structural and electronic properties with the most pronounced in energy gap. The amplitude for the positive clusters is bigger than both the neutral and negative clusters. The neutral clusters with even number of even-coordinated atoms are more stable than the neighbors with odd number of even-coordinated atoms, as is completely reversed for the charged clusters. The oscillatory behaviors for the charged clusters are opposite to that for the neutral clusters, as is attributed to the electron-paired effect.

Reducing the voltage loss of Y-series acceptor based organic solar cells via ternary/quaternary strategies

In recent years, with the emergence of non-fullerene fused-ring acceptors, power conversion efficiencies (PCEs) of organic solar cells (OSCs) have exceeded 19%.However, compared to inorganic or perovskite photovoltaic cells, a higher voltage loss has become one of the key factors limiting further improvement in the PCEs of OSCs.The ternary/quaternary strategy has been identified as a feasible and effective way to obtain high-efficiency OSCs.In this review, a brief outline is given of the key roles that guest materials played in reducing voltage losses in solar cell devices and a brief look at the future material design and the design of ternary/quaternary systems.

DFT study on nonlinear optical properties of lithium-doped corannulene

The effects of lithium doping on the nonlinear optical properties of new electrodes (lithium-doped corannulene) were investigated in detail. Nine dynamically stable geometries of Lin-C20H10 (n=1, 2) are predicted by B3LYP/6-31G(d,p). Among these nine structures, the largest first static hyperpolarizability (β0) is computed to be 15314 au, which is dramatically larger than the β0 value of 74 au for C20H10, indicating that Li doping plays an important role in elevating the first hyperpolarizability of corannulene.

Structures,Aromaticity and Raman Spectroscopy of Double Hanging Ring Molecules[(GnHn-1^m)(GnHn-1^m)](G=C,Si,Ge;n=3,5,6,7,8;m=+1,-1,0,+1,+2)

Theoretical calculations of Double Hanging Ring Molecule(DHRM) [(GnHn-1^m)(GnHn-1^m)](G=C,Si,Ge;n=3,5,6,7,8;m=+1,-1,0,+1,+2) were performed via Gaussian 09 with the method of Density Functional Theory(DFT). Geometrical optimization, Potential Energy surface Scan(PES), Degree of Aromaticity(DOA) and Nucleus Independent Chemical Shift(NICS) were computed to study the optimal structures and aromaticity of DHRMs. Ring Stretching Vibration Raman Spectroscopy(RSVRSF) was predicted to seek the relation between RSVRSF and aromaticity of DHRMs. The results show optimal structures of DHRMs[(GnH(n-1)~m)(GnH(n–1)~m)](n = 3, 5~8);DA = 90° is the stable structure when n = 3, 7, 8;while n = 5 corresponds to DA = 30°, n = 6 corresponds to DA = 50°;the correlation between DOA and NICS of DHRMs is quadratic;the value of RSVRSF of DHRM approximates to its corresponding single ring molecule, which could act as characteristic frequency of ring molecule to identify its aromaticity;the correlation between RSVRSF and DOA is quadratic, and that between RSVRSF and NICS is linear.

Electronic properties and photodegradation ability of Nd-TiO_(2)for phenol

In this study,the photocatalytic activity of Nd-TiO_(2)photocatalysts obtained by common hydrothermal method was evaluated by practical experiments and theoretical calculations based on density functional theory(DFT).The synthesized photocatalysts were characterized by X-ray diffraction(XRD),N_(2)adsorption-desorption,Fourier transform infrared spectroscopy(FT-IR),high resolution transmission electron microscopy(HRTEM),X-ray photoelectron spectroscopy(XPS),UV-Vis diffuse reflectance spectroscopy(DRS),and photoluminescence(PL)to study their physical/chemical prope rties.At the same time,the photoelectronic performance was also investigated.The photodegradation ability of asprepared photocatalysts and the effect of Nd doped amount and photocatalysts dosage were investigated by the photodegradation of phenol(30 mg/L)under 400 W metal halide lamp(UV-Vis).The effect of Nd on electronic properties of TiO_(2)and adsorption ability of phenol were discussed.Results show the red-shift wavelength of 0.5 mol%Nd-TiO_(2),indicating that its absorption capacity is stronger than pristine TiO_(2)in the same wavelength range.The result of DFT calculations demonstrates that the optical bandgap of Nd-TiO_(2)is profoundly reduced,thus the light absorption ability is promoted,which will be responsible for the enhanced photocatalytic performance of Nd-TiO_(2).0.5 mol%Nd is an optimum value for photodegradation phenol,and phenol can be completely degraded by 0.5 mol%Nd-TiO_(2)for 210 min,the higher catalytic performance is derived from the efficient separation of e-/h+pairs.Moreover,the adsorption energy calculations of phenol on TiO_(2)(101)and Nd-TiO_(2)(101)demonstrate that the Nd doping can significantly enhance the adsorption ability of phenol on catalyst surfaces because of the formation of Nd-O bonds.At last,the stability measurement through four recycles exhibits that 0.5 mol%Nd-TiO_(2)possesses excellent stability.

Preparation of Photoresponsive PAN-NH_(2)@EPESP Fiber Films with Mechanical Stability for Regulating Wettability and Micro-environment Humidity

In view of the current living micro-environment and requirements of green economy,intelligent light-responsive humidification materials have become a hot spot in intelligent polymer materials.In this work,reversible photoresponsive films with a mechanical stability and an excellent humidity adjustment performance are developed by modifying epoxy-ether-spiropyran(EPESP)on amino-nanofibers(PAN-NH2),which was produced through electrospinning.Such smart films for regulating wettability and micro-environment humidity can be reversibly manipulated by the simple switch of UV and visible light irradiation because of the unique transformation between polar ring-opened status and nonpolar ring-closed status of the spiropyran units.The effects of EPESP modification amount on the morphology,wettability,tensile strength and the ability to regulate humidity were investigated in detail.The results show that with the increase of modification amount of EPESP,both the humidity regulation and tensile strength increased;when the modification amount exceeds 7 mg,the range of regulating humidity increases slowly.

Understanding ultra-dispersed CeO_(x)modified iridium clusters as bifunction electrocatalyst for high-efficiency water splitting in acid electrolytes

Designing bifunctional catalysts with high catalytic activity and durability for electrochemical water splitting has become a promising approach to producing clean and sustainable hydrogen fuels.With high specific surface area and ultra-small size,metal clusters have become a kind of promising catalysts.By introducing Ce species,the noble metal iridium(Ir)can be electronically modulated,thus reduce the activation energy of intermediate,and improve the intrinsic catalytic activity for practical application.The performance of Ir_(3)CeO_(x)/C is more prominent among different feeding ratios of the precursor.The overpotential is only 299 mV for the oxygen evolution reaction(OER),and the overpotential is only23 mV for the hydrogen evolution reaction(HER)at 10 mA/cm^(2) in acid media.The Ir doped with appropriate amount of Ce can obtain excellent OER and HER performance and catalyze water splitting efficiently.This work provides a strategic approach to the formation of clusters of precious metals and rare earths.

Chlorinated phthalimide polymer donor as ultra-wide bandgap and deep HOMO guest for achieving highly efficient polymer solar cells

Quaternary approach has been receiving more and more attention due to its effectiveness in improving solar cell performance, while synthesis/selection of the fourth component is yet a key issue. Herein, we report a chlorinated phthalimide based donor polymer(namely Ph I-Cl) having an ultra-wide bandgap(2.10 e V) and a deep HOMO(-5.58 e V) level. Addition of Ph I-Cl as the third component of PM6:Y6 and the fourth of PM6:Y6:PC71BM increases both hole and electron mobilities and gives rise to more balanced charge carriers mobilities. Both the short-circuit current-density and fill-factor are increased and open-circuit voltage is well maintained, delivering 17.0% and 18.1% efficiencies, respectively. These results demonstrate that chlorination on the side thiophene of phthalimide-based donor polymer is a way to make deep HOMO and ultra-wide bandgap donor polymer guest used for highly efficient ternary and quaternary strategies.

Nano palladium catalyzed C(sp^(3))-H bonds arylation by a transient directing strategy

Reported herein is the first example of heterogeneous palladium catalyzed C(sp^(3))-H bonds arylation by a transient-ligand-directed strategy.Using supported palladium(metallic state) na nopariticles as catalyst,a wide range of aryl iodides undergo the coupling with various o-methylbenzaldehyde derivatives to assemble a library of highly selective and functionalized o-benzylbenzaldehydes.The stability of the catalyst was easily recovered four runs without significant loss of activity.The XPS analysis of the catalyst before and after reaction indicated that the reaction might be carried out by a catalytic cycle starting with Pd~0.

From amides to urea derivatives or carbamates with chemospecific C–C bond cleavage at room temperature

Ureas and carbamates are common motifs in pharmaceuticals,agrochemicals,biologically active com-pounds and organocatalysis applications.Herein,we report a significant advancement in this area and present a general method for copper-catalyzed chemospecific C–C bond cleavage of amides to syn-thesize urea derivatives and carbamates at room temperature.