NiFe-Coordination Polymers-Derived Layered Double Hydroxides as Bifunctional Materials: Effect of the Ni : Fe Ratio on the Electrochemical Performance.

The development of an efficient and cost-effective material is highly desirable for electrochemical devices such as electrolyzers and supercapacitors. Especially, pseudomorphic transformations of metal-organic frameworks (MOFs)/coordination polymers (CPs) into layered double hydroxides (LDHs) materials endow well-defined porosities, high surface area, exchangeable interlayer anions and easily adjustable electronic structure that are truly required for oxygen evolution reaction (OER) and high-performance supercapacitor applications. Herein, we have prepared NiFe-LDHs of various Ni/Fe ratios via a facile room-temperature alkaline hydrolysis of NiFe-CPs precursors. Electrochemical studies reveal that the catalyst having high amount of Fe (Ni1.2 Fe1 -LDH) showed the better OER activity with a low Tafel slope (65 mV dec-1 ) in 1 M KOH. On the other hand, the catalyst containing higher amount of Ni with better layered structure (Ni11.7 Fe1 -LDH) showed high performance for supercapacitor (702 F g-1 at 0.25 A g-1 ) in 3 M KOH. Moreover, a solid-state asymmetric supercapacitor device Ni11.7 Fe1 -LDH/AC was fabricated which exhibited a specific capacitance of 18 F g-1 at a current density of 1 A g-1 . The device displayed high cycling stability with 88% of capacitance retention after 7000 cycles. The experimental findings in this work will help in the futuristic development of NiFe-LDH based electrocatalysts for the enhanced electrochemical performances.

Correction: Engineering the morphology of palladium nanostructures to tune their electrocatalytic activity in formic acid oxidation reactions.

[This corrects the article DOI: 10.1039/D0NA00798F.].

Engineering the morphology of palladium nanostructures to tune their electrocatalytic activity in formic acid oxidation reactions.

Pd nanomaterials can be cheaper alternative catalysts for the electrocatalytic formic acid oxidation reaction (FAOR) in fuel cells. The size and shape of the nanoparticles and crystal engineering can play a crucial role in enhancing the catalytic activities of Pd nanostructures. A systematic study on the effect of varying the morphology of Pd nanostructures on their catalytic activities for FAOR is reported here. Palladium nanoparticles (Pd0D), nanowires (Pd1D) and nanosheets (Pd2D) could be synthesized by using swollen liquid crystals as 'soft' templates. Swollen liquid crystals are lyotropic liquid crystals that are formed from a quaternary mixture of a surfactant, cosurfactant, brine and Pd salt dissolved in oil. Pd1D nanostructures exhibited 2.7 and 19 fold higher current density than Pd0D and Pd2D nanostructures in the FAOR. The Pd1D nanostructure possess higher electrochemically active surface area (ECSA), better catalytic activity, stability, and lower impedance to charge transfer when compared to the Pd0D and Pd2D nanostructures. The presence of relatively higher amounts of crystal defects and enriched (100) crystal facets in the Pd1D nanostructure were found to be the reasons for their enhanced catalytic activities.

Zn(ii)-based coordination polymer: An emissive signaling platform for the recognition of an explosive and a pesticide in an aqueous system.

A new emissive Zn(ii)-based coordination polymer (Zn-CP) bearing paddle-wheel clusters has been developed and the same has been demonstrated to have potential for recognising a nitroaromatic-based explosive (TNP) and a pesticide (2,6-DCNA) in aqueous solution. The structural integrity of this newly developed 2D material was established through single-crystal analysis, whereas the stability of Zn-CP in aqueous medium after the recognition process was investigated by the powder-XRD technique. A combination of experimental and theoretical studies revealed that the change in fluorescence intensity of Zn-CP while interacting with TNP and 2,6-DCNA was possibly due to simultaneous operation of PET and FRET. Experimentally, it was also established that Zn-CP can be reused in up to three cycles for the detection of TNP and 2,6-DCNA.