Niobium-Incorporated CoSe2 Nanothorns with Electronic Structural Alterations for Efficient Alkaline Oxygen Evolution Reaction at High Current Density.

Developing cost-effective, highly active, and robust electrocatalysts for oxygen evolution reaction (OER) at high current density is a critical challenge in water electrolysis since the sluggish kinetics of the OER significantly impedes the energy conversion efficiency of overall water splitting. Here, a 1D nanothorn-like Nb-CoSe2 /CC (CC=carbon cloth) structure was developed as an efficient OER catalyst. The optimized Nb-CoSe2 /CC catalyst exhibited remarkable OER performance with the low overpotentials of 220 mV at 10 mA cm-2 and 297 mV 200 mA cm-2 and a small Tafel slope (54.1 mV dec-1 ) in 1.0 m KOH electrolyte. More importantly, the Nb-CoSe2 /CC electrode displayed superior stability after 60 h of continuous operation. In addition, cell voltages of 1.52 and 1.93 V were required to achieve 10 and 500 mA cm-2 for the electrolyzer made of Nb-CoSe2 /CC (anode) and the Pt/C (cathode). Density functional theory (DFT) calculations combined with experimental results revealed that incorporating niobium into the CoSe2 could optimize the adsorption free energy of the reaction intermediates and enhance the conductivity to improve the catalytic activity further. Additionally, the super-hydrophilicity of Nb-CoSe2 /CC resulting from the surface defects increased the surface wettability and facilitated reaction kinetics. These results indicate that Nb-CoSe2 /CC intrinsically enhances OER performance and possesses potential practical water electrolysis applications.

Co4S3 grafted 1 T-phase dominated WS2 ultrathin nanosheet arrays for highly efficient overall water splitting in alkaline media.

Developing the earth-abundant transition metal-based bifunctional electrocatalysts for water splitting and renewable energy devices has attracted much attention. Herein, we report a 1 T-WS2 in ultrathin nanosheet arrays grafted with Co4S3 on conductive carbon cloth (CC) (1 T-Co4S3-WS2/CC) through a feasible in-situ growth and vulcanization. The optimized 1 T-Co4S3-WS2/CC catalyst exhibits an impressive electrocatalytic activity and remarkable stability with the oxygen/hydrogen evolution reaction (OER/HER: 278/75 mV for 10 mA cm-2). It also showed the small Tafel slope values of 61.7 and 58.4 mV dec-1, respectively. Additionally, the 1 T-Co4S3-WS2/CC(-/+) achieved 1.59 V@10 mA cm-2 in alkaline media superior to the most previously reported non-precious metal electrocatalysts. The outstanding performance could be attributed to the synergy between heterostructures of Co4S3 and 1 T-WS2 modifying the electronic structure to accelerate water splitting kinetics. Thus, this work presents a rational design of scalable, high-efficiency, stable water splitting electrocatalysts based on WS2.

[Ag15(N-triphos)4(Cl4)](NO3)3: a stable Ag-P superatom with eight electrons (N-triphos = tris((diphenylphosphino)methyl)amine).

A first and stable Ag-P superatom nanocluster [Ag15(N-triphos)4(Cl4)](NO3)3 (1) has been successfully synthesized and characterized. X-ray analysis shows that this Ag15 cluster has a hexacapped body-centered cubic (bcc) framework which is consolidated by four tripodal N-triphos ligands. The identity of 1 is confirmed by high resolution ESI-MS. Cluster 1 has an electronic and geometric shell closure structure with 8 free electrons, matching the stability idea of superatom theory for a nanocluster. DFT calculation of this Ag15 cluster reveals the superatom feature with a 1S21P6 configuration. The chelation of multidentate phosphines enhances the stability of this Ag15 cluster. The AgAg distances between the centered and the vertical Ag atoms of this bcc (Ag@Ag8) are in the range of 2.57-2.71 Å, and the distances between the face-capped and the vertical silver atoms are in the range of 2.84-2.92 Å, showing strong AgAg interactions within this cluster core. This superatom complex exhibits a relatively high thermal and photolytic stability.

Synthesis, structural characterization and luminescent properties of a series of Cu(I) complexes based on polyphosphine ligands.

A series of Cu(I) complexes with a [Cu(NN)(PP)](+) moiety, [Cu(phen)(pba)](BF(4)) (1a), [Cu(2)(phen)(2)(pbaa)](BF(4))(2) (2a), [Cu(2)(phen)(2)(pnaa)](BF(4))(2) (3a), [Cu(2)(phen)(2)(pbbaa)](BF(4))(2) (4a), [Cu(dmp)(pba)](BF(4)) (1b), [Cu(2)(dmp)(2)(pbaa)](BF(4))(2) (2b), [Cu(2)(dmp)(2)(pnaa)](BF(4))(2) (3b) and [Cu(2)(dmp)(2)(pbbaa)](BF(4))(2) (4b) (phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, pba = N,N-bis((diphenylphosphino)methyl)benzenamine, pbaa = N,N,N',N'-tetrakis((diphenylphosphino)methyl)benzene-1,4-diamine, pnaa = N,N,N',N'-tetrakis((diphenylphosphino)methyl)naphthalene-1,5-diamine and pbbaa = N,N,N',N'-tetrakis((diphenylphosphino)methyl)biphenyl-4,4'-diamine), were rationally designed and synthesized. These complexes were characterized by (1)H and (31)P NMR, electrospray mass spectrometry, elemental analysis and X-ray crystal structure analysis. Introduction of different central arene spacers (phenyl, naphthyl, biphenyl) into ligands, resulting in the size variation of these complexes, aims to tune the photophysical properties of the complexes. Each Cu(I) ion in these complexes adopts a distorted tetrahedral geometry constructed by the chelating diimine and phosphine groups. Intermolecular C-H···π and/or π···π interactions are involved in the solid states. The dmp-containing complex exhibits better emission relative to the corresponding phen complex due to the steric encumbrance of bulky alkyl groups. Furthermore, for complexes with identical diimine but different phosphine ligands, the tendency of increased emission lifetime as well as blue-shifted emission in the solid state follows with the decrease in size of complexes. Intermolecular C-H···π interactions have an influence on the final solid state photophysical properties through vibrationally relaxed non-radiative energy transfer in the excited state. Smaller-sized complexes show better photophysical properties due to less vibrationally relaxed behavior related to flexible C-H···π bonds. Nevertheless, the tendency for increased quantum yield and emission lifetime, as well as blue-shifted emission in dilute solution goes with the increase in size of complexes. The central arene ring (phenyl, naphthyl or biphenyl) has an influence on the final photophysical properties. The larger the π-conjugated extension of central arene ring is, the better the photophysical properties of complex are. The rigid and large-sized complex 3b, with a high quantum yield and long lifetime, is the best luminophore among these complexes.

[Theoretical calculation of vibrational frequencies for clusters of (1,2-micro2-L1)(1,2-micro2-L2)-decacarbonyltriosmium [L1, L2=H, Cl, Br, I]].

Density functional theory (DFT) and ab initio method have been employed to optimize the molecular geometry of (1,2-micro2-H) (1, 2-micro2-L) Os3 (CO)10 (L: Cl, Br, I) at B3LYP/CEP-4G, B3LYP/LanL2DZ, RHF/CEP-4G and RHF/LanL2DZ levels, respectively. By using ab initio method, the authors have optimized the molecular geometry of (1,2-t12 -L)2 Os3 (CO)20 (L: H, Cl, Br, I). The calculations showed that the charge was translated from Os(CO)3 to Os(CO)4. Harmonic vibrational analysis was performed at the RHF/CEP-4G levels, and according to the frequencies and intensities of the equilibrium structure obtained by using ab initio method, the IR spectra of structure have been simulated. The calculated results were compared with each other and with available experimental data, and were discussed in detail.

The 2'-deoxyadenosine-5'-phosphate anion, the analogous radical, and the different hydrogen-abstracted radical anions: molecular structures and effects on DNA damage.

The 2'-deoxyadenosine-5'-phosphate (5'-dAMP) anion and its related radicals have been studied by reliably calibrated theoretical approaches. This study reveals important physical characteristics of 5'-dAMP radical related processes. One-electron oxidation of the 5'-dAMP anion is found on both the phosphoryl group and the adenine base with electron detachment energies close to that of phosphate. Partial removal of electron density from the adenine fragment leads to an extended pi system which includes the amine group of the adenine. Although the radical-centered carbon increases the extent of bonding with its adjacent atoms, it usually weakens the chemical bonds between the atoms at the alpha- and beta-positions. This tendency should be important in predicting the reactivity of the sugar-based radicals. The overall stability sequence of the H-abstracted 5'-dAMP anionic radicals is consistent with the analogous results for the H-abstracted neutral radicals of the adenosine nucleoside: aliphatic radicals > aromatic radicals. The negatively charged phosphoryl group attached to atom C(5)' of the ribose does not change this energetic sequence. All the H-abstraction produced 5'-dAMP radical anions are distonic radical anions. Studies have shown that the charge-radical-separating feature of the distonic radical anions is biologically relevant. This result should be important in understanding the reactive properties of these H-abstraction-produced anion radicals.