Evolution of novel nanostructured MoCoFe-based hydroxides composites toward high-performance electrochemical applications: Overall water splitting and supercapacitor

Metal hydroxides are versatile and appealing electrode materials owing to their merits such as easy room-temperature synthesis, nanostructures formation, higher conductivity, crystallite or non-crystallite formation, porous structures, etc. Herein, nanostructured ternary transition metal (M = Mo, Co, Fe) hydroxides (TTMHs) are successfully grown on nickel foams via template-free single-step electrodeposition for overall water splitting and supercapacitor applications. Interestingly, numerous element ratios of Mo5+, Co2+, and Fe3+ in the electrodeposition precursor solutions manifested novel nanostructures viz nanosheets, nanoflakes, nanoparticles, and nanograss-like structures were evolved for different precursor solutions. For water splitting, a negative electrode prepared using aqueous Mo:Co:Fe (4.0:4.0:2.0 M ratio) metal salt solution that exhibited excellent hydrogen evolution activity with 98 mV overpotential, whereas a positive electrode (Mo:Co:Fe = 3.0:3.5:3.5) shows efficient oxygen evolution with 227 mV overpotential, and a full cell assembled from these active electrodes exhibited lower 1.56 V cell voltage at 10 mAcm(-2). For the supercapacitor, a working electrode with composition Mo:Co:Fe = 6.0:2.0:2.0 showed 3354.7 mFcm(-2) high areal capacitance at 1.0 mAcm 2 with excellent retention (91% after 3000 cycles). An asymmetric supercapacitor (ASC) device was fabricated that exhibited enormous energy and power densities of 1.27 x 10(-3) Whcm(-3) and 3.75 Wcm(-3), respectively. The high-performances of both devices (water splitting full cell and supercapacitor) are due to the unique composition of hybrid electrodes (with nanostructured morphology) and synergistic effects. The present investigation demonstrates a simple strategy for preparing potential TTMHs composite electrodes with the evolution of different morphologies for multiple electrochemical applications.

Automated summary

Metal hydroxides, such as nanostructured ternary transition metal (M = Mo, Co, Fe) hydroxides, are versatile and appealing electrode materials with easy synthesis, high conductivity, and porous structures. These materials show promise in applications such as water splitting and supercapacitors due to their unique composition and evolved nanostructures. For water splitting, electrodes with different metal salt solutions exhibit excellent hydrogen and oxygen evolution activities. For supercapacitors, the working electrode with a specific composition shows high areal capacitance and excellent retention. The hybrid electrodes and synergistic effects contribute to the high performance of both water splitting full cells and supercapacitors.