Synthesis of Off‐Stoichiometric CoS Nanoplates from a Molecular Precursor for Efficient H₂/O₂ Evolution and Supercapacitance

Abstract

The development of cost-effective and easily accessible bifunctional materials, which can be effectively used for energy storage and energy generation, is highly desirable. Herein, a new molecular precursor [tris(morpholinodithiocarbamato)Co (III)] has been synthesized and the X-ray crystal structure of the complex determined. The precursor was used to prepare oleylamine (OLA)-capped cobalt sulfide nanoplatelets, using a facile hot injection method at two different temperatures (200°C and 260°C). The characterization of the samples shows that CoS synthesized at 200°C is slightly sulfur rich, whereas CoS synthesized at 260°C is slightly cobalt rich. The effect of off-stoichiometry of CoS nanoplatelets on the energy gener-ation and storage applications was studied. The oxygen evolution reaction catalytic performance of both samples indicate overpotentials of 307 and 276 mV as well as Tafel slopes of 96 and 82 mV/dec, respectively. Similarly, overpotentials of 132 and 153 mV were observed for the hydrogen evolution reaction, with Tafel slopes of 159 and 154 mV/dec, respectively. The capacitive behavior of the samples was also examined, and specific capacitance values of 298 and 440 F/g were obtained with cycling stabilities of 73 and 97 %, after 5000 cycles, respectively. The results indicate that sulfur-deficient CoS can show superior performance for efficient energy generation and storage devices.[a] C.

Effect of NiO on organic framework functionalized ZnO nanoparticles for energy storage application

“…The presence of organic functional groups were also revealed by the C1s spectrum in figure 4c. In agreement with Furlan et al, 2014, Oswald et al, 2018 and Gervas et al, 2019 C 1s spectrum is fitted with peaks at binding energies of 284.8 eV (C=C, C–C, C–H), 286.4 eV (C–O–C, C–OH) and 288.5 eV (C=O) . We note that any sample exposed to atmosphere will have a layer of adsorbed hydrocarbon but the presence of significant amounts of O‐containing organic species appears to indicate the functionalization of ZnO@NiO by organic species, therefore suggesting stabilization of the nanomaterials by organic compounds of E. cognata .…”

“…The Figure B presented the total impedance as the function frequency. The impedance of ZnO@NiO was found to be decreased in the present investigation which is consistent to the Gervas et al and Bhoyate et al Thus, the lower total impedance furthered designated the better conductive characteristics of ZnO@NiO. These results indicated good electrical conductivity of fabricated electrode with Faradic reactions.…”

“…Finally, the storage potential of fabricated electrode was estimated by energy density ( E ) as well as power density ( P ) using discharge voltage via following equations and expressed as W h kg −1 and W kg −1 ; where C is capacitance via GCD, ∆ V ( V ) is applied window, and t (s) is discharge time . In the present research, maximum calculated energy density of ZnO@NiO was 3.13 against power density of 138.…”

“…The Ragone plot (Figure C) depicts that when power density increased, the energy density was decreased and vice versa. Negative correlation between energy density and powder density is a general phenomena associated with numerous other fabricated supercapcitors …”

Flexible Molecular Precursors for Selective Decomposition to Nickel Sulfide or Nickel Phosphide for Water Splitting and Supercapacitance

“…These prepared samples were allowed to dry completely at room temperature, viewed for TEM and HRTEM at accelerating voltages of 120 and 200 kV, respectively. Images were acquired by using the iTEM software (TEM) and Gatan software (HRTEM) …”