Graphitic Carbon Nitride-Induced Multifold Enhancement in Electrochemical Charge Storage of CoS–NiCo₂S₄ for All-Solid-State Hybrid Supercapacitors

Abstract

In order to improve the electro-microstructural physiognomics of electrode materials for applications in better efficiency supercapacitors, herein graphitic carbon nitride (GCN)heterostructurized CoS−NiCo 2 S 4 is designed using a controlled material growth synthesis procedure. The developed CoS− NiCo 2 S 4 /GCN possesses ample hydrophilicity, possible charge transfer between GCN and CoS−NiCo 2 S 4 , uniform phase distribution, and distinctive microstructural characteristics. The preliminary electrochemical studies in the three-electrode setup show GCN-induced lower charge transfer resistance and very unique Warburg profile corresponding to extremely low diffusion resistance in CoS−NiCo 2 S 4 /GCN as compared to pristine CoS− NiCo 2 S 4 . Furthermore, GCN is found to significantly induce surface-controlled (capacitive-type) charge storage and frequency-independent specific capacitance up to 10 Hz in CoS−NiCo 2 S 4 . Furthermore, the CoS−NiCo 2 S 4 ||N-rGO and CoS−NiCo 2 S 4 /GCN||N-rGO all-solid-state hybrid supercapacitor (ASSHSC) devices were fabricated using N-rGO as the negative electrode material, and the inducing effect of GCN on the supercapacitive charge storage performance of the devices is thoroughly studied. Results demonstrate that the mass specific capacitance and areal capacitance of CoS−NiCo 2 S 4 /GCN||N-rGO are ∼2 and ∼4 times more than those of the CoS−NiCo 2 S 4 ||N-rGO ASSHSC device, respectively. Furthermore, the CoS−NiCo 2 S 4 /GCN||N-rGO offers more energy density, rate energy density, and additional charge− discharge durability (over ∼10,000 cycles) than the CoS−NiCo 2 S 4 ||N-rGO ASSHSC device. The multifold performance improvement of CoS−NiCo 2 S 4 with GCN heterostructurization is ascribed to GCN-induced supplemented porosity and pore widening, ionic nonstoichiometry (Ni 2±δ , Co 2±δ , and Co 3±δ ), wettability, integrated enhancement in the conductivity, and electroactive-ion accessibility in the CoS−NiCo 2 S 4 /GCN heterocomposite. The present study offers vital physicoelectrochemical insights toward the future development of low cost and high-performance electrode materials, and their implementation in high-rate and operationally stable all-solid-state hybrid supercapacitor devices, for application in the next-generation front-line technologies.

Hierarchical Mn3O4/NiSe2–MnSe2: A Versatile Electrode Material for High-Performance All-Solid-State Hybrid Pseudocapacitors with Supreme Working Durability

“…The isotherm clearly shows the inherence of mesopores (signature hysteresis in the P / P 0 region of ∼0.4–0.9) and macropores (signature hysteresis in the P / P 0 region of ∼0.9–1.0) due to the intercrystallite and interparticle porosity, respectively, in Mn 3 O 4 /NiSe 2 –MnSe 2 . Furthermore, the BJH pore size distribution profile shows the presence of signature pores in the mesopore and macropore regions. , The BET specific surface area and BJH specific pore volume of Mn 3 O 4 /NiSe 2 –MnSe 2 were estimated to be 78 m 2 g –1 and 0.13 cm 3 g –1 , respectively. This study justifies richly accessible surface of Mn 3 O 4 /NiSe 2 –MnSe 2 for electrochemical reactions.…”

“…It is noteworthy that the decrease in the diffusion-controlled charge-storage component is only 16% with a 5-fold increase in the scan rate, which evidently shows the facilitated diffusion of OH – ions in the bulk matrix of Mn 3 O 4 /NiSe 2 –MnSe 2 and easier accessibility of OH – ions to the electroactive sites (redox-active metal ions) of Mn 3 O 4 /NiSe 2 –MnSe 2 even under the elevated rate condition . The output current ( i ) can be expressed as a function of scan rate according to the power law as expressed in equation , italici = italica ν italicb where i is the anodic peak current density and a and b are the process constants. The constant b can be obtained from the slope of a linear fitted log i vs log v plot.…”

“…The specific capacity ( C SC , C g –1 ) values of Mn 3 O 4 /NiSe 2 –MnSe 2 at various applied current densities ( i in A g –1 ) were estimated by utilizing the discharge time ( Δt in s) under the respective current density condition and mass ( m in g) of Mn 3 O 4 /NiSe 2 –MnSe 2 in equation . Furthermore, the specific capacitance ( C S , F g –1 ) values of Mn 3 O 4 /NiSe 2 –MnSe 2 at various applied current densities ( i in A g –1 ) were estimated by utilizing the discharge time ( Δt in s) under the respective current density condition, mass ( m in g) of Mn 3 O 4 /NiSe 2 –MnSe 2 , and operating voltage window ( ΔV in volts) in equation . , italicC italicS italicC = italici × normalΔ italict italicm italicC italicS = italici × normalΔ italict italicm × normalΔ italicV Mn 3 O 4 /NiSe 2 –MnSe 2 shows C SC values of 608, 565, 372, 280, and 225 C g –1 and C S values of 1521, 1413, 932, 699, and 564 F g –1 at respective current densities of 2, 4, 8, 12, and 16 A g –1 . The plots of ( C SC and C S ) vs applied current density are shown in Figure F.…”

“…In this context, electrochemical energy storage systems are considered to be the most sustainable alternative among several such perceptive systems . High-performance electrochemical energy storage devices have numerous advantages such as longer lifecycles, high Ragone efficiency (high energy density at elevated power density conditions), and significant reversibility as well as portability . Among several essential electrochemical energy storage devices, supercapacitors are significant in the context of delivering equally high power and energy density, extended operational stability, and diverse applicability .…”

“…In this regard, the presence of more dynamic redox-active species in the electrode material and low-impedance kinetics of the redox reactions lead to enhanced charge transfer and improve the essential balance between the energy and power delivery of a pseudocapacitor . Fundamentally, the generation of more dynamic redox-active species and the improvement of the kinetics of redox reactions can be achieved by the targeted physicochemical design of an electrode material with suitable physicoelectrochemical physiognomies for multiple redox reactions and facilitated charge-transfer kinetics. ,− In the context of electrode materials for pseudocapacitors, transition-metal chalcogenides, i.e., oxides and selenides in particular, are most favorable because the oxides offer compound redox-active species (metal ions), selenides possess higher electrical conductivity, and the oxides and selenides in combination show excellent electrochemical activity as well as electromicrostructural stability . Notably, the synergetic effect is a fundamental property in mixed-phase materials due to the formation of active phases by the chemical interaction between two phases, the formation of mobile oxygen species, interphase charge transfer, and supplemented chemical reactivity.…”