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 (Ni1.2Fe1-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 (Ni11.7Fe1-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 Ni11.7Fe1-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.