Selenide-based 3D folded polymetallic nanosheets for a highly efficient oxygen evolution reaction.

Electrochemical water splitting, which is considered to be one of the fruitful strategies to achieve efficient and pollution-free hydrogen production, has been deemed as a key technology to achieve renewable energy conversion. Oxygen evolution reaction (OER) is a decisive step in water splitting. Slow kinetics seriously limits the effective utilization of energy thus it is extremely urgent to develop electrocatalysts that can effectively reduce the reaction energy barrier thus accelerate OER kinetics. Here, Mn-Co0.85Se/NiSe2/NF nanosheets with 3D folded structure was assembled on Ni foam by electrodeposition and vapor-deposition method. Mn-Co0.85Se/NiSe2/NF can achieve a current density of 10 mA cm-2 with only 175 mV overpotential in an alkaline environment of 1 M KOH, which is much lower than other reported catalysts. In addition, catalyst Mn-Co0.85Se/NiSe2/NF also performed well in long-term stability tests. Through the synergy of polymetallic, the improvement of catalyst surface energy together with the tuning of electronic structure and the optimization of conductivity can be realized. This work may provide a feasible strategy for the design of efficient selenide-based oxygen evolution reaction catalysts.

Assembly of ZIF-67 nanoparticles and in situ grown Cu(OH)2 nanowires serves as an effective electrocatalyst for oxygen evolution.

Due to the slow kinetics of oxygen evolution at the anode, the efficiency of electrocatalytic water decomposition is critically reduced, and its large-scale application is severely restricted. Therefore, it is urgent to develop electrocatalysts with excellent performance and stability to accelerate the oxygen evolution reaction (OER) reaction kinetics. Herein, a self-supporting binder-free electrocatalyst was successfully prepared using in situ grown Cu(OH)2 nanowires on CF as the carrier to grow ZIF-67 via a room temperature immersion method. The combination of Cu(OH)2 nanowires and the unique structure of ZIF-67 forms a three-dimensional nanostructured catalyst, in which the unique structure and the existence of synergy may contribute to a larger electrochemical active surface area, expose more electrochemically active sites, adjust the electronic structure, and accelerate the rate of electron transfer, thus greatly improving the electrocatalytic activity and durability for OER. The as-prepared Cu(OH)2@ZIF-67/CF exhibited excellent OER performance under alkaline conditions and required overpotentials of 205 mV and 276 mV to drive current densities of 10 mA cm-2 and 100 mA cm-2, respectively, with a small Tafel slope of 70.5 mV dec-1 for OER. The stability test of Cu(OH)2@ZIF-67/CF at the current density of 10 mA cm-2 displayed excellent stability for 22 h. This study provides a feasible strategy for the rapid preparation of low-cost and efficient electrocatalysts in alkaline media.

Ruthenium-doped NiFe-based metal-organic framework nanoparticles as highly efficient catalysts for the oxygen evolution reaction.

Developing highly efficient and stable electrocatalysts toward the oxygen evolution reaction (OER) is essential for large-scale sustainable energy conversion and storage technologies. Herein, we design and synthesize a ruthenium (Ru) doped NiFe bimetallic metal-organic framework (MOF) deposited on the nickel foam (Ru-NiFe-MOF/NF) by a facile one-pot hydrothermal reaction. Ru-NiFe-MOF/NF exhibits favourable electrocatalytic OER activity in alkaline solution, and requires a low overpotential of 205 mV to achieve 10 mA cm-2, a small Tafel slope of 50 mV dec-1, and long-term electrochemical stability over 100 h. This work demonstrates the rational nano-architectural design and synthesis of predominantly efficient and robust cation-doped MOF-derived materials for energy catalysis and beyond.

Hydration and swelling: a theoretical investigation on the cooperativity effect of H-bonding interactions between p-hydroxy hydroxymethyl calix[4]/[5]arene and H2O by many-body interaction and density functional reactivity theory.

In order to explore the nature of the hydration and swelling of superabsorbent resin, a theoretical investigation into the cooperativity effect of the H-bonding interactions in the hydrates of four model compounds that can be regarded as the units of hydroquinone formaldehyde resin (HFR) (i.e., O-hydroxymethyl-1,4-dihydroxybenzene, methylene di-O-hydroxymethyl-1,4-dihydroxybenzene, p-hydroxy hydroxymethyl calix[4]arene and p-hydroxy hydroxymethyl calix[5]arene) was carried out by many-body interaction and density functional reactivity theory. The HFR···H2O···H2O complexes, in which the H2O···H2O moieties are bound with both the hydroxyl groups of HFR, are the most stable. For the HFR(H2O)n clusters, the interaction energy per building block is increased as the number of the size n increases, indicating the cooperativity effect. Therefore, a deduction is given that the cooperativity effects of the H-bonding interactions play an important role in the process of the hydration and swelling of HFR, and the swelling behavior is mainly attributed to the cooperativity effects which arised from the interactions between the H2O molecules. The origin of the cooperativity effect was examined employing several information-theoretic quantities in the density functional reactivity theory. The degree of swelling of HFR was quantitated using a measure of volume. Graphical abstract.

5-Diethyl-amino-2-{[2-(2,4-dinitro-phen-yl)hydrazin-1-yl-idene]meth-yl}phenol.

In the title compound, C(17)H(19)N(5)O(5), obtained from the condensation reaction of 4-diethyl-amino-2-hy-droxy-benzalde-hyde and 2,4-dinitro-phenyl-hydrazine, the two benzene rings are twisted by a dihedral angle of 1.75 (12)°. The nitro groups are slightly twisted with the respect to the benzene ring to which they are attached, making dihedral angles of 8.20 (15) and 5.78 (15)°. An intra-molecular O-H⋯N hydrogen bond occurs. In the crystal, mol-ecules are linked by pairs of inter-molecular N-H⋯O hydrogen bonds, forming dimers through R(2) (2)(12) rings. These dimers are further linked by C-H⋯O and C-H⋯π and weak slipped π-π inter-actions [centroid-centroid distance = 3.743 (2)Å]. One of the ethyl groups is disordered over two positions, with occupancy factors in the ratio 0.72:0.28.

Bis[4-hy-droxy-3,5-dimeth-oxy-benzalde-hyde (2,4-dinitro-phen-yl)hydrazone] N,N-dimethyl-formamide disolvate monohydrate.

In the title compound, 2C(15)H(14)N(4)O(7)·2C(3)H(7)NO·H(2)O, the hydrazone mol-ecules are roughly planar, with the two benzene rings twisted slightly relative to each other by dihedral angle of 6.04 (11) and 7.75 (11)° in the two mol-ecules. The water mol-ecule is linked to the Schiff base mol-ecule by an O-H⋯O hydrogen bond. Intra-molecular N-H⋯O hydrogen bonds occur. In the crystal, mol-ecules are linked by inter-molecular N-H⋯O and O-H⋯O hydrogen bonds.

2-Hydroxy-3-methoxybenzaldehyde 2,4-dinitrophenylhydrazone pyridine monosolvate.

The Schiff base molecule of the title compound, C(14)H(12)N(4)O(6)·C(5)H(5)N, was obtained from the condensation reaction of 2-hy-droxy-3-meth-oxy-benzaldehyde and 2,4-dinitro-phenyl-hydrazine. The C=N bond of the Schiff base has a trans arrangement and the dihedral angle between the two benzene rings is 3.49 (10)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring. In the crystal, O-H⋯O hydrogen bonds link the Schiff base mol-ecules.

3-Eth-oxy-2-hy-droxy-benzaldehyde 2,4-di-nitro-phenylhydrazone N,N-di-methyl-formamide monosolvate.

The Schiff base of the title compound, C(15)H(14)N(4)O(6)·C(3)H(7)NO, was obtained from the condensation reaction of 3-eth-oxy-2-hy-droxy-benzaldehyde and 2,4-dinitro-phenyl-hydrazine. The dihedral angle between the benzene rings is 3.05 (10)° and intra-molecular N-H⋯O and O-H⋯O hydrogen bonds generate S(6) and S(5) ring motifs, respectively. In the crystal, the Schiff base and dimethyl-formamide solvent mol-ecules are linked by an O-H⋯O hydrogen bond.