Anchoring γ-MnO2 within β-NiCo(OH)2 as an Interfacial Electrode Material for Boosting Power Density in an Asymmetric Supercapacitor Device and for Oxygen Evolution Catalysis.

The great challenge is to improve the high-competence electrochemical supercapacitor (ES) and oxygen evolution reaction (OER) electrocatalyst with earth-abundant transition metals rather than using limited noble metals. Herein, we developed a facile strategy to introduce two different phases such as α-MnO2 or γ-MnO2 on porous hexagonal bimetallic β-NiCo(OH)2-layered double hydroxide (LDH) nanosheets for an enhanced bifunctionality and to ease out interfacial redox reaction kinetics. Due to the rational intend of LDH morphology and well-retained starlike γ-MnO2 nanostructures, the bifunctional LDHs exhibit commendable activities toward ESs and in the OER study. Importantly, the γ-MnO2 phase loaded at β-NiCo(OH)2 LDHs shows superior ESs or electrocatalytic OER performance in comparison with the α-MnO2 phase on LDHs. Besides, the assembled fabricated asymmetric supercapacitor (FASC) device possesses convincing energy (24.43 W h/kg) and power densities (5312 W/kg) and enabled us to glow a 1.4 V light-emitting diode for 45 s. Accordingly, three-/two-electrode systems or the solid-state FASC device has exhibited high efficiency in ESs. Also, the optimized γ-MnO2 phase on β-NiCo(OH)2 LDHs with the detailed mass ratio of Ni and Co has displayed the OER performance comparable to commercial RuO2. The electrochemical studies and structural classifications offer in-depth analysis on the electrochemical behaviors, especially the stability in both ES and OER studies, signifying a promising aspirant in the alternative energy field.