Egg shell membrane template stabilises formation of β-NiMoO4 nanowires and enhances hybrid supercapacitor behaviour

Abstract

Adding an eggshell membrane (ESM) template to the solution combustion synthesis of NiMoO 4 resulted in the formation of -NiMoO 4 under mild conditions. It is postulated that the unique nature of the ESM template results in interactions that stabilise this difficult to synthesise form of NiMoO 4 .The ESM template led to -NiMoO 4 particles that were nano-wire like in shape and arranged in an open weave structure that significantly enhanced the mesoporosity and conductance of the material. The specific capacitance was measured as 259 F g-1 in a two electrode system with an energy density of 252.2 W h kg-1. The results indicate that the use of a fibrous like natural polymeric materials as templates stabilises materials in preferred crystal forms and shapes leading to much improved electrochemical performance. Keywords Superconductors, Energy storage and conversion, Nickel molybdate, template, nanowire, eggshell membrane 1 Introduction Large-scale uptake of clean and sustainable energy generation has led to much effort being devoted to the development of novel energy storage solutions to cater for the intermittent nature of the energy output from these renewable sources [1-6]. Supercapacitors are considered a promising technology in this area as they provide higher power and energy density than traditional batteries coupled with fast recharge ability, high energy storage capability, good rate performance, and long cycling stability [7]. Traditionally, supercapacitors have been available in two forms based on their charge storage mechanism. Electrical double-layer capacitors (EDLC) store energy at the electrode/electrolyte interface, while pseudocapacitors utilise electron transfer faradaic reactions in a suitable electrolyte. Hybrids of these traditional forms are now being actively investigated where both storage mechanisms can be accessed, resulting in devices with much higher capacitance and a broader range of applications [8,9]. An essential part of the development of hybrid supercapacitors is the investigation of novel active materials for electrode manufacture [10-12 ]. Mixed metal oxides are a promising area due to the availability of multiple oxidation states and relative earth abundant starting materials [13-16]. Mixed metal molybdates, especially those incorporating Ni, are particularly interesting materials, exhibiting high specific capacitance and energy density [17-20]. This improved performance is attributed to the fact that NiMoO 4 is more chemically active than other molybdates (Mg, Co, etc.) and exhibit a greater density of oxidation states near the top of the valence band [21,22]. There are two main ways to increase the performance of a hybrid supercapacitor electrode: increase the surface area and manipulate the material to improve conductance. The former can be achieved by synthesising nano-sized particles with interesting shapes or a porous nature that allow maximum access to the surface of the material or by simply increasing porosity without resorting to the nanoscale [23-25]. Improvement in c...

Binder-Free Electrospun Ni–Mn–O Nanofibers Embedded in Carbon Shells with Ultrahigh Energy and Power Densities for Highly Stable Next-Generation Energy Storage Devices

“…Compared with carbonaceous materials, TMOs can store charges at the electrode surface via faradic reactions. TMOs have the advantage of exhibiting a higher specific capacitance, ensuring a high energy density. − Among all the previously reported oxides, − manganese oxides (Mn x O y ) and nickel oxides (Ni x O y ) gained tremendous attention for supercapacitor application due to their several benefits, including their high theoretical capacity (∼1360 and ∼2584 F/g for manganese and nickel oxides, respectively), ,, abundancy, cost-efficiency, low toxicity, and multi-oxidation states that ensure an efficient redox charge transfer and enhancing pseudocapacitive behavior. Mn x O y also provides a wide operating voltage window in neutral aqueous electrolytes. ,,,, However, similar to other metal oxides, there are some drawbacks that limit their efficient use in supercapacitors, including agglomeration of the particles that limits the available surface active sites and increases the resistivity, poor mechanical stability, intrinsic low electrical conductivity, and the poor long-term cycling stability. ,,,, To overcome these limitations, Kolathodi et al reported beaded manganese oxide (Mn 2 O 3 ) nanofibers prepared via the surfactant-free electrospinning method, which revealed a capacitance of 358 F/g at 0.5 A/g.…”

Concave Ni(OH)2 Nanocube Synthesis and Its Application in High-Performance Hybrid Capacitors

“…Figure 5 a shows the CV curves of the Ni(OH) 2 electrode for various scan rates within the potential window range of 0 to 0.5 V versus SCE. All CV curves exhibit a pair of redox peaks caused by the faradaic reaction Ni(OH) 2 + OH − ⇄ NiOOH + H 2 O + e − [ 31 , 34 ], implying the battery-type materials of the Ni(OH) 2 electrode [ 35 , 36 , 37 , 38 ]. As the scan rate increases, the anodic and cathodic peaks shift toward higher and lower potentials, respectively, without a significant change in the shape of the CV profiles, revealing that the Ni(OH) 2 electrode enables rapid redox reactions.…”

Addition of MnO2 in synthesis of nano-rod erdite promoted tetracycline adsorption

“…Thus, the redox reaction of the Fe-S bond in erdite is subordinate in comparison with the hydrolysis of erdite. MnS is similarly hydrolysed, and the Mn 2+ obtained is oxidised to MnOOH in the presence of dissolved oxygen 51 , which oxidises HS − at ambient condition (Fig. 10, step 2) 45 .

Figure 10Illustration of TC adsorption by erdite particles.

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