Sphere-like Naphthalene-Based Microporous Nickel Phosphonate Facile for Asymmetric Supercapacitor Devices and Bifunctional Oxygen Electrocatalysts

Abstract

To produce clean energy due to the lack of fossil fuels, the development of cost-effective and highly efficient energy storage devices and multifunctional electrocatalysts is essential to substitute noble metal-based electrocatalysts. In this context, transition metal-based nickel phosphonate material (NiNAP) has been synthesized using 1,1′-binaphthyl-2,2′-diyl hydrogenphosphate and nickel nitrate hexahydrate in a hydrothermal reaction pathway in the absence of a templating pathway. The organic− inorganic hybrid structure with microporous arrays as a potential electrode material facilitates energy storage and conversion reactions. For the first time, a sphere-like NiNAP material has been developed, which is a potential electrode material for asymmetric supercapacitor applications with high specific capacitance and both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) with a low overpotential and higher current density. Moreover, the NiNAP material exhibits a specific capacitance of 4456 F g −1 in three-electrode assembly and 455 F g −1 in asymmetric supercapacitor at a scan rate of 1 mV s −1 , where the energy and power density are estimated to be 204 W h kg −1 and 409 W kg −1 , respectively. Interestingly, the NiNAP material displays outstanding catalytic activity toward OER with a low overpotential of 242 mV at the current density of 10 mA cm −2 and excellent ORR activity with an onset potential of 0.74 V vs RHE. Also, it shows long-term stability without significant changes in the current density for OER and ORR.

Bifunctional Role of Methyl Viologen in UV and X-ray Sensitive Switchable Organophosphonate Single Crystal

“…Despite the few X-ray-induced photochromic materials, recently viologen and their analogues, especially the methyl viologen (MV; N , N ′-dimethyl-4,4′-bipyridinium), holding an electron-deficient nature, have been considered to be ideal candidates to exhibit prominent UV and X-ray-induced photochromism with assistance of a suitable electron-rich moieties via efficient electron transfer pathway. ,− Generally, it can be seen that the methyl viologen based compounds can form different photogenerated intermediate species such as neutral MV 0 , radical cation MV •+ , or dication MV 2+ , depending upon the coordination behaviors of electron-rich units during photochromic redox process. − Moreover, incorporation of the MV into an organophosphonate compound can create more opportunity for isolating novel organic–inorganic hybrid structures as compared to earlier explored various traditional inorganic anions, holding fewer coordination opportunities. − Particularly, electron rich oxygen atoms of the organophosphonate moiety bind with different metal ions by diverse coordination linkages that often exhibit versatile architectures including interesting topologies. − MV regulated hybrid organophosphonate structure and X-ray induced photochromic behavior is still underdeveloped in the field of material chemistry.…”

Superior Electrochemical Water Splitting and Energy-Storage Performances of In Situ Fabricated Charge-Separated Metal Organophosphonate Single Crystals

“…1,20,23,42,47,50,60 It is mostly observed due to the weak adhesion during applied current for a long period in a strong electrolyte medium (acidic/alkaline) as well as the high production rate of gas bubbles on the electrode surface, as communicated in earlier reports. 20,23,42,47,50,54 More importantly, to get insights into the origin of high catalytic activity of catalyst NIT1 toward OER and HER, we have determined the turn over frequency (TOF) at overpotentials of 342 mV (for OER) and 276 mV (for HER), respectively (see details in the Supporting Information and Figure S20). 34,44,47,54,56 Impressively, the calculated TOF values for both OER and HER reactions are found to be 28.23 and 39.92 s −1 , respectively, and well consistent with their lowest overpotential and Tafel slope values of catalyst NIT1.…”

“…Here, the minimum contribution of organophosphonate moieties may support as a proton acceptor that was kinetically more facile under electrocatalytic environment. 23,42,50,56 It is worth noting that the in situ formation of the methyl viologen group in compound NIT1 not only improves the structural stability but also promotes the superior catalytic OER/HER activities of the present catalyst. Moreover, the present catalyst (NIT1) also obeyed the common OER/HER mechanistic pathway that was wellinvestigated earlier for many phosphonate-based electrocatalysts.…”

Metal–organic framework and graphene composites: advanced materials for electrochemical supercapacitor applications

“…Different kinds of materials, including metal oxides, metal phosphides, graphene derivatives, covalent-organic frameworks (COFs), MOFs, and porous carbon materials, have been reported for their application in supercapacitors. 7,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] In 1995, Yaghi and co-workers discovered MOFs, and since then MOFs have been widely used in various applications. 67 This term became more popular when Yaghi and coworkers discovered the structure of MOF-5.…”