Electrodeposited MnS on graphene wrapped Ni-Foam for enhanced supercapacitor applications

MnS-BaS Heterostructures as Effective Catalysts for Oxygen Reduction Reaction

The inadequate electrical conductivity of metal sulfides, along with their tendency to agglomerate, has hindered their use in energy storage and catalysis. The construction of a heterojunction can ameliorate these deficiencies to some extent. In this paper, MnS-BaS heterojunction catalysts were prepared by a hydrothermal method, which is a simple and inexpensive process. The MnS-BaS heterojunction catalysts exhibited superior performance owing to the strong synergistic interaction between MnS and BaS. Density functional theory (DFT) calculations reveal strong interactions at the heterojunction interface and significant electron transfer between MnS and BaS, which further modulates the electronic structure of Mn. The elevation of the center of the d-band enhances the adsorption of oxygen and oxygen-containing intermediates on the catalyst, thus promoting the oxygen reduction reaction (ORR). The practical application of MnS-BaS catalysts was tested by assembling zinc-air batteries. This study provides a rational strategy for designing transition metal catalysts that are efficient and low cost.

Recent Developments in Electrodeposition of Transition Metal Chalcogenides-Based Electrode Materials for Advance Supercapacitor Applications: A Review

High-performance supercapacitive electrode materials have received significant attention from researchers worldwide, thus aiming for comparable performance similar to the extensively used rechargeable batteries. For emerging energy storage technologies like flexible supercapacitors, transition metal chalcogenides (TMCs) have been in the spotlight due to their promising electrochemical features compared to other electrode materials. Among the synthesis techniques, electrodeposition-mediated preparation of thin films of TMCs offered an affordable binder-free approach for electrode fabrication that effectively improved the supercapacitor performance. Hence, this review mainly focussed on the electrodeposition-based syntheses of single/ multinary chalcogenides and their composites for supercapacitors applications. Further, the effects of different deposition parameters were discussed for boosting the supercapacitor performance. Finally, this review outlined the existing challenges and future perspectives in this research domain, which will assist the upcoming exploration in the energy storage field.

Surface charge induced self-assembled nest-like Ni3S2/PNG composites for high-performance supercapacitors

The paper presents a self-assembly approach to synthesize Ni3S2/N, P co-doped graphene (PNG) composite electrode materials for supercapacitors with high energy storage performance and structural stability. Innovatively, the self-assembly approach is induced via the surface charge effect utilizing a two-step hydrothermal method. The doping of nitrogen (N) and phosphorus (P) atoms regulates the surface charge distribution on graphene nanosheets. Therefore, in the synthesized Ni3S2/PNG heterostructures, Ni3S2 nanowires are interwoven into nests and uniformly attached to PNG. The design of the electrode materials with such a special structure not only supports each other to improve the stability of the materials but also facilitates the rapid diffusion of electrolyte ions. Based on the advantages of composition and structure, Ni3S2/PNG has a high specific capacitance of 1117C g-1 at a current density of 1 A/g and excellent rate performance. The asymmetric supercapacitors (ASC) assembled with Ni3S2/PNG and PNG as positive and negative materials respectively have a high energy density of 62 Wh kg-1 at a power density of 158 W kg-1.

Efficient photocatalytic degradation of ciprofloxacin by graphite felt-supported MnS/Polypyrrole composite: Dominant reactive species and reaction mechanisms

The accumulation of antibiotics in aquatic environments poses a serious threat to human health. Photocatalytic degradation is a promising method for removing antibiotics from water, but its practical implementation requires improvements in photocatalyst activity and recovery. Here, a novel graphite felt-supported MnS/Polypyrrole composite (MnS/PPy/GF) was constructed to achieve effective adsorption of antibiotics, stable loading of photocatalyst, and rapid separation of spatial charge. Systematic characterization of composition, structure and photoelectric properties indicated the efficient light absorption, charge separation and migration of the MnS/PPy/GF, which achieved 86.2% removal of antibiotic ciprofloxacin (CFX), higher than that of MnS/GF (73.7%) and PPy/GF (34.8%). The charge transfer-generated 1O2, energy transfer-generated 1O2, and photogenerated h+ were identified as the dominant reactive species, which mainly attacked the piperazine ring in the photodegradation of CFX by MnS/PPy/GF. The •OH was confirmed to participate in the defluorination of CFX via hydroxylation substitution. The MnS/PPy/GF-based photocatalytic process could ultimately achieve the mineralization of CFX. The facile recyclability, robust stability, and excellent adaptability to actual aquatic environments further confirmed MnS/PPy/GF is a promising eco-friendly photocatalyst for antibiotic pollution control.

Li-S Chemistry of Manganese Phosphides Nanoparticles With Optimized Phase

The targeted synthesis of manganese phosphides with target phase remains a huge challenge because of their various stoichiometries and phase-dependent physicochemical properties. In this study, phosphorus-rich MnP, manganese-rich Mn₂ P, and their heterostructure MnP-Mn₂ P nanoparticles evenly dispersed on porous carbon are accurately synthesized by a convenient one-pot heat treatment of phosphate resin combined with Mn²⁺ . Moreover, their electrochemical properties are systematically investigated as sulfur hosts in lithium-sulfur batteries. Density functional theory calculations demonstrate the superior adsorption, catalysis capabilities, and electrical conductivity of MnP-Mn₂ P/C, compared with MnP/C and Mn₂ P/C. The MnP-Mn₂ P/C@S exhibits an excellent capacity of 763.3 mAh g^-1 at 5 C with a capacity decay rate of only 0.013% after 2000 cycles. A phase evolution product (MnS) of MnP-Mn₂ P/C@S is detected during the catalysis of MnP-Mn₂ P/C with polysulfides redox through in situ X-ray diffraction and Raman spectroscopy. At a sulfur loading of up to 8 mg cm^-2 , the MnP-Mn₂ P/C@S achieves an area capacity of 6.4 mAh cm^-2 at 0.2 C. A pouch cell with the MnP-Mn₂ P/C@S cathode exhibits an initial energy density of 360 Wh kg^-1 .

Simultaneous Improvement of Oxygen Reduction and Catalyst Anchoring via Multiple Dopants on Mesoporous Carbon Frameworks for Flexible Al-Air Batteries

Mesoporous carbon supported non-noble metals, as promising catalysts for boosting the oxygen reduction reaction (ORR) in metal-air batteries, usually face challenges of low activity and performance degradation caused by the catalyst detachment from carbon substrates. Herein, a one-stone-two-birds strategy is reported to simultaneously improve the ORR activity and anchor nanosized MnS catalysts on a mesoporous carbon framework via nitrogen (N) and sulfur (S) dopants (MnS/NS-C). Synchrotron-based X-ray absorption spectroscopy (XAS) confirms the existence of Mn-N and Mn-S bonds, which firmly anchor active MnS nanoparticles. Density functional theory (DFT) calculations reveal that the N, S codoping lowers the d-band center of Mn and optimizes ORR intermediate adsorption. An excellent ORR performance (the onset and half-wave potential of 1.07 and 0.91 V) and long-term durability are achieved for MnS/NS-C in alkaline media. The flexible Al-air battery, using MnS/NS-C as the cathode catalyst, shows a power density of 134.6 mW cm^-2 in comparison to the Pt/C-based counterpart of 106.2 mW cm^-2. This study constructs a stable interaction with non-noble catalysts and carbon substrates for enhancing catalytic activity and durability in metal-air batteries.

Wrinkle-Shaped Nickel Sulfide Grown on Three-Dimensional Nickel Foam: A Binder-Free Electrode Designed for High-Performance Electrochemical Supercapacitor Applications

Recently, three-dimensional nickel foam (3D-Nf) has been increasingly studied; however, further modifications in nanoscale surface modification are necessary for particular applications. In this work, three-dimensional hierarchically porous nanogranular NiS (NiS-3D-Nf) and wrinkle-shaped NiS (w-NiS-3D-Nf) structures were fabricated directly on nickel foam by a simple one-step solvothermal process using two different solvents. Several characterization techniques, including X-ray diffraction pattern, X-ray photoelectron spectroscopy, and scanning electron microscopy, were used to characterize the samples’ properties. To prove their applicability, supercapacitor electrodes were tested directly in a three-electrode assembly cell. The resulting w-NiS-3D-Nf electrodes exhibited greater capacitive activity than the NiS-3D-Nf electrodes. The optimized w-NiS-3D-Nf electrodes delivered an excellent specific capacitance of 770 Fg−1, at a current density of 1 Ag−1, compared with the NiS-3D-Nf electrodes (162.0 Fg−1 @ 1 Ag−1), with a cyclic stability of over 92.67% capacitance retention after 2200 cycles. The resultant unique structure with integrated hierarchical three-dimensional configuration can not only enhance abundant accessible surface areas but also produce strong adhesion to the 3D-Nf, facilitating the fast transportation of ions and electrons for the electrochemical reaction via the conductive 3D-Nf. This set of results suggests that the modification of 3D-Nf surfaces with a suitable solvent has highly significant effects on morphology, and ultimately, electrochemical performance. Additionally, the current preparation approach is simple and worthwhile, and thus offers great potential for supercapacitor applications.

Adsorption and photocatalysis removal of arsenite, arsenate, and hexavalent chromium in water by the carbonized composite of manganese-crosslinked sodium alginate

The preparation of easily synthesized and cheap composite materials for the efficient removal of toxic oxoanions still remains challenging in sewage treatment. Herein, a new carbonized manganese-crosslinked sodium alginate (Mn/SA-C) was fabricated for the removal of arsenite (As(III)), arsenate (As(V)) and hexavalent chromium (Cr(VI)) in water. The results indicated that the Mn/SA-C pretreated with MnSO₄ solution (Mn/SA-C-S) exhibited a rapid adsorption toward As(III) and As(V) with the removal efficiency of >98% within 10 min, and had a high adsorption capacity toward As(III), As(V), and Cr(VI) with the maximum value of 189.29, 193.29, and 104.50 mg/g based on the Langmuir model, respectively. The removal efficiency of As(III), As(V), and Cr(VI) could be further significantly enhanced by coupling a photocatalytic process. For example, the time in which >98% of Cr(VI) (10 mg/L) was removed dramatically shortened from 360 min (adsorption) to 45 min (adsorption-photocatalysis), and the removal efficiency of As(III) increased by ∼10% within initial 5 min. This was primarily attributed to the Mn-catalyzed production of the photocatalytic excitons for Cr(VI) reduction, and the superoxide (•O₂^-) and hydroxyl (•OH) radicals for As(III) oxidation. The adsorption removal of arsenic (As) was primarily ascribed to surface complexation with MnO and precipitation by MnS₂, and oxidative adsorption because of Mn valence cycle. The removal mechanisms of Cr(VI) mainly contained reduction by MnO and MnS₂, complexation with MnO and carboxyl/hydroxyl groups as well as Cr(OH)₃ precipitation. Our research provides a promising Mn/SA-C-S material for rapid and efficient removal of As(III), As(V), and Cr(VI) in contaminated water through an adsorption-photocatalysis synergistic strategy.

Electrochemical approach toward reduced graphene oxide-based electrodes for environmental applications: A review

Graphene has shown great potential in various application fields due to its excellent carrier transportation, ultra-high specific surface area, good mechanical properties, and light transmittance. However, pure graphene still exhibits some insurmountable defects, such as difficulty in simple and large-scale preparation, and limitations in application. The electrochemical method is a simple, clean, and environmentally friendly method. The rapid and simple preparation of graphene and its derivatives by electrochemical methods has important environmental significance. Moreover, rGO-based nanohybrids can be prepared by convenient and quick electrodeposition or cyclic voltammetry (CV), or to change the morphology and structure of graphene and its derivatives to achieve the purpose of improving material properties. This work mainly summarizes electrochemically related graphene from four aspects: (i) the method of electrochemical exfoliation of graphene; (ii) types of electrodeposition rGO-based nanohybrids; (iii) electrochemical regulation of the structure of rGO-based mixtures; (iv) environmental applications of rGO-based nanohybrids prepared by electrodeposition. This article critically discusses the advantages and disadvantages of electrochemical-related graphene, outlines future challenges, and provides insightful views and references for other researchers.

An atom-economy route for the fabrication of α-MnS@C microball with ultrahigh supercapacitance: The significance of in-situ vulcanization

In this study, we have introduced a facile, effective and low-cost process of in-situ vulcanization for preparing α-MnS@C composite via simple calcination-thermolysis of one manganese coordination polymer (CP-1-ZX). In this procedure, the 1D chain [-Mn-SO₄-]_∞ in CP-1-ZX is completely reduced into α-MnS by the as-synthesized carbon. So the in-situ vulcanization provides an atom-economy route to fabricate sulfides by using least synthetic steps and sulfur sources. The α-MnS@C composite maintains the microball morphology of CP-1-ZX precursor, which is composed of many core-shell nanoparticles. Due to high porosity, hierarchical pores and good conductivity, the specific capacitance of α-MnS@C is up to 856F g^-1 at 0.5 A g^-1, and keeps 82% retention after 5000 cycles. Meanwhile, one asymmetric supercapacitor cell (ASC) is assembled by combining α-MnS@C with commercial active carbon (AC). The α-MnS@C//AC device delivers prominent energy density of 28.4 Wh kg^-1 at power density of 395 W kg^-1, and still retains 17.8 Wh kg^-1 at 8020 W kg^-1. Furthmore, four tandem ASC devices can brightly glow a lamp bulb for 30 s. Therefore, the α-MnS@C composite shows great applications in supercapacitors.

Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

High specific energy supercapacitor electrode prepared from MnS/Ni3S2 composite grown on nickel foam

Herein, MnS was prepared in situ with Ni3S2 directly on nickel foam to obtain a novel binder-free highly conductive electrode with a superb echinocactus-like morphology.