Direct solvent free synthesis of bare α-NiS, β-NiS and α-β-NiS composite as excellent electrocatalysts: Effect of self-capping on supercapacitance and overall water splitting activity

Abstract

Nickel sulfide is regarded as a material with tremendous potential for energy storage and conversion applications. However, it exists in a variety of stable compositions and obtaining a pure phase is a challenge. this study demonstrates a potentially scalable, solvent free and phase selective synthesis of uncapped α-niS, β-niS and α-β-niS composites using nickel alkyl (ethyl, octyl) xanthate precursors. Phase transformation and morphology were observed by powder-X-ray diffraction (p-XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The comparative efficiency of the synthesized samples was investigated for energy storage and generation applications, in which superior performance was observed for the niS synthesized from the short chain xanthate complex. A high specific capacitance of 1,940 F/g, 2,150 F/g and 2,250 F/g was observed at 2 mV/s for bare α-niS, β-niS and α-β-NiS composite respectively. At high current density of 1 A/g, α-niS showed the highest capacitance of 1,287 F/g, with 100% of Coulombic efficiency and 79% of capacitance retention. In the case of the oxygen evolution reaction (oeR), β-NiS showed an overpotential of 139 mV at a current density of 10 mA/cm 2 , with a Tafel slope of only 32 mV/dec, showing a fast and efficient process. It was observed that the increase in carbon chain of the synthesized self-capped nickel sulfide nanoparticles decreased the overall efficiency, both for energy storage and energy generation applications. As a step towards the implementation of sustainable energy development strategies, research on the design of high-performance energy storage and conversion systems is gathering renewed momentum 1-3. Sodium ion batteries (SIBs), lithium-ion batteries (LIBs), and supercapacitors (SCs) are examples of the most studied energy storage devices 4,5. Energy conversion systems on the other hand, constitute a series of electrochemical reactions occurring in an electrolytic cell or in a hydrogen-oxygen fuel cell 3. Hydrogen is a clean and sustainable energy carrier, currently regarded as the best alternative fuel of the future 6,7. Its generation via the electrocatalytic splitting of water is a commonly investigated energy conversion technology 8. The performance of both energy storage devices and energy conversion systems is largely influenced by the type of electroactive material employed. Generally, for energy conversion systems the goal is to develop low cost, earth-abundant and efficient electrocatalysts that will replace Pt-, Ir-and Ru-based compounds 9 , while for energy storage devices, the goal is to develop advanced electrode materials that can deliver high energy and power densities 10. Carbon-based materials 11 , conductive polymers 12 , transition metal oxides 13 , nitrides 14 , carbides 14 , phosphides 15 , and sulfides 5 are among the materials investigated for both energy storage and generation applications. Owing to their low cost, high electrochemical activity as well as mechanical and thermal stability, transition

Solventless synthesis of nanospinel Ni1−xCoxFe2O4 (0 ≤ x ≤ 1) solid solutions for efficient electrochemical water splitting and supercapacitance

“…It is an environmentally benign, scalable and straightforward approach in which precursor materials undergo solid-state decomposition by thermal treatment. 35,36 Compared with the most frequently used solution-based techniques, this approach ensures an inexpensive synthesis of nanoscopic oxide materials with surfaces free of any insulating surfactants. The surfactants adhere to the active surfaces of the catalyst and block/reduce the interaction of reactant molecules with the active sites.…”

Synthesis and characterization of zinc di(O-2,2-dimethylpentan-3-yl dithiocarbonates) bearing pyridine or tetramethylethylenediamine coligands and investigation of their thermal conversion mechanisms towards nanocrystalline zinc sulfide

“…Furthermore, several studies reported in literature show that features of the final metal sulfide nanomaterials such as the size, phase and shape, can be controlled by the nature of the capping agents 51 or the type of the alkyl chain. 52,53 In this contribution, we report on the synthesis and crystal structure of two new zinc xanthate complexes bearing 2,2-dimethylpentan-3-yl alkyl moieties and additional either pyridine or N,N,N′,N′-tetramethylethylenediamine (TMEDA), as coligand. In addition, we extend our study to the investigation of the thermal decomposition of these compounds.…”

Boosting Oxygen Evolution Reaction on Metallocene‐based Transition Metal Sulfides Integrated with N‐doped Carbon Nanostructures

“…Similarly, Ni 2p spectra in the Ni 9 S 8 /Ni 3 S 2 −NC (Figure 3c) can be fitted and divided into two satellite peaks with three spin‐orbit doublet peaks. The first, second, and third doublet peaks appeared at 851.3 and 869.2 eV, 853.4 and 871.4 eV, and 854.5 and 872.8 eV, which can be indexed correspondingly to the binding energies of Ni 2p 3/2 and Ni 2p 1/2 core levels of Ni metal atoms with less valence oxidation state (Ni <1+ ), Ni 2+ , and Ni 3+ [20–22] . The satellite peaks are detected at around 859 and 877 eV [23] .…”