Electrodeposited Ni(OH)(2) on nickel foam with porous and 3D nanostructures has ultrahigh capacitance in the potential range -0.05-0.45 V, and a maximum specific capacitance as high as 3152 F g(-1) can be achieved in 3% KOH solution at a charge/discharge current density of 4 A g(-1).

Metal organic frameworks (MOFs), an emerging class of nanoporous crystalline materials, have become increasingly attractive for solar energy applications. In this work, we report a newly designed mixed-node MOF catalyst, Co x Fe1–x -MOF-74 (0 < x ≤ 1), which acts as a highly efficient electrocatalyst for oxygen evolution reaction (OER) in alkaline solution with remarkably low overpotential (280 mV at a current density of 10 mA/cm2), small Tafel slope (56 mV/dec), and high faradic efficiency (91%) and can deliver a current density of 20 mA/cm2 at 1.58 V for overall water splitting. Moreover, using the combination of multiple spectroscopic methods, including X-ray absorption, electron spin resonance, and X-ray photoelectron spectroscopy, etc., we unraveled the mechanistic origin of the enhanced catalytic performance of Co x Fe1–x -MOF-74 compared to its single-metal counterparts. We show the mixed-node MOF can provide more open metal sites and an enhanced electron-rich environment, which facilitates efficient charge transfer and results in significantly enhanced OER activity.

A new series of five three-dimensional Ln(III) metal-organic frameworks (MOFs) formulated as [Ln(μ-L)(μ-HCOO)(μ-OH)(μ-O)(DMF)(HO)] {Ln = Tb (1), Eu (2), Gd (3), Dy (4), and Er (5)} was successfully obtained via a solvothermal reaction between the corresponding lanthanide(III) nitrates and 2-(6-carboxypyridin-3-yl)terephthalic acid (HL). All of the obtained compounds were fully characterized, and their structures were established by single-crystal X-ray diffraction. All products are isostructural and possess porous 3D networks of the fluorite topological type, which are driven by the cubane-like [Ln(μ-OH)(μ-O)(μ-HCOO)] blocks and μ-L spacers. Luminescent and sensing properties of 1-5 were investigated in detail, revealing a unique capability of Tb-MOF (1) for sensing acetone and metal(III) cations (Fe or Ce) with high efficiency and selectivity. Apart from a facile recyclability after sensing experiments, the obtained Tb-MOF material features a remarkable stability in a diversity of environments such as common solvents, aqueous solutions of metal ions, and solutions with a broad pH range from 4 to 11. In addition, compound 1 represents a very rare example of the versatile Ln-MOF probe capable of sensing Ce or Fe cations or acetone molecules.

The exploration of highly efficient nonprecious metal bifunctional electrocatalysts to boost oxygen evolution reaction and oxygen reduction reaction is critical for development of high energy density metal-air batteries. Herein, a class of CuS/NiS 2 interface nanocrystals (INs) catalysts with atomic-level coupled nanointerface, subtle lattice distortion, and plentiful vacancy defects is reported. The results from temperature-dependent in situ synchrotron-based X-ray absorption fine spectroscopy and electron spin resonance spectroscopy demonstrate that the lattice distortion of 14.7% in CuS/NiS 2 caused by the strong Jahn-Teller effect of Cu, the strong atomic-level coupled interface of CuS and NiS 2 domains, and distinct vacancy defects can provide numerous effective active sites for their excellent bifunctional performance. A liquid Zn-air battery with the CuS/NiS 2 INs as air electrode displays a large peak power density (172.4 mW cm −2 ), a high specific capacity (775 mAh g Zn −1 ), and long cycle life (up to 83 h), making the CuS/NiS 2 INs among the best bifunctional catalysts for Zn-air battery. More remarkably, the flexible CuS/NiS 2 INsbased solid-state Zn-air batteries can power the LED after twisting, making them be promising in portable and wearable electronic devices.

Electrochemical activation is an effective and simple method to obtain in-situ surface modification of MOF materials away from thermal decomposition. However, the impact of the rate and related phase transformation on OER intrinsic activity during the electrochemical activation process is often overlooked. Herein, we synthesized a kind of Co-MOF with a unique crystal structure in which the center metals were coordinated with the oxygen and nitrogen atoms from two water molecules and organic linkers. The bond strength between the center metals and the coordinated water molecules can be modulated by introducing Fe into Co-MOF, causing the expedited electrochemical activation. First-principles calculations suggest the electronic state of cobalt in CoFe-MOF can be modified to alter the free energy of adsorbed intermediates. Therefore, the obtained electrocatalyst possesses the optimal OER intrinsic activity, showing a low overpotential of 265 mV at 10 mA cm–2, a small Tafel slope of 44 mV dec–1, and a long-term electrochemical durability with a period of 40 h. The findings are expected to help understand the fundamental principles of electrochemical activation.

Well-ordered NiFe-MOF-74 is in situ grown on Ni foam by the induction of Fe2+ and directly used as an OER electrocatalyst. Benefited from the intrinsic open porous structure of MOF-74, the in situ formed MOF arrays and the synergistic effect of Ni and Fe, outstanding water oxidation activity is obtained in alkaline electrolytes with an overpotential of 223 mV at 10 mA cm-2.

The electrochemical splitting of water, as an efficient and large-scale method to produce H, is still hindered by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. Considering the synergetic effect of the different metal sites with coordination on the surface of electrocatalysts, the hybrids of Co/Fe phosphides (denoted as Co-Fe-P) is prepared by one-step phosphorization of CoFe metal-organic frameworks for the first time as highly efficient electrocatalysts for OER. Benefiting from the synergistic effect of Co and Fe, the high valence of Co ions induced by strongly electronegative P and N and the large electrochemical active surface area (ECSA) originated from exposed nanowires on the surface of Co/Fe phosphides, the resultant Co-Fe-P-1.7 exhibits remarkable electrocatalytic performances for OER in 1.0 M KOH, affording an overpotential as low as 244 mV at a current density of 10 mA/cm, a small Tafel slope of 58 mV/dec, and good stability, which is superior to that of the state-of-the-art OER electrocatalysts. In addition, the two-electrode cell with Co-Fe-P-1.7 modified Ni foam as anode and cathode in an alkaline electrolyte, respectively, exhibits the decomposition potential of ca. 1.60 V at a current density of 10 mA/cm and excellent stability.

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