Ultrathin MoS2 Nanosheets Research Articles

Hollow ZnS-SnS2@MoS2 Heterostructures for High-Efficiency Adsorption-Storage- Catalysis of Polysulfides in Lithium-Sulfur Batteries

Heterostructure catalysts show promise in facilitating the conversion between sulfur, soluble polysulfides, and solid Li2S2/Li2S in Li-S batteries due to their rapid electron/ion transfer properties. However, most catalysts lack sufficient specific surface area and high catalytic activity to achieve timely adsorption and catalysis of polysulfides. Herein, hollow ZnS-SnS2@MoS2 heterostructures are firstly synthesized, which combine the strong absorption capacity with high catalytic activity to ensure a remarkable electrochemical performance. The hollow ZnS-SnS2 heterogeneous cubes serve as a highly active component with an extraordinary bidirectional electrocatalytic capability for polysulfide conversion. Additionally, ultrathin MoS2 nanosheets with large specific surface areas are coated on the ZnS-SnS2 cubes to enhance polysulfide absorption and eliminate concentration overpotential. The hollow space in ZnS-SnS2@MoS2 heterostructures acts as a reservoir for sulfur and intermediate polysulfides, effectively suppressing the shuttle effect. With these advantages, the ZnS-SnS2@MoS2 heterostructures exhibit a synergistic adsorption-storage-catalysis effect for polysulfides. Consequently, the Li-S batteries assembled with the ZnS-SnS2@MoS2-modified separators demonstrate superior electrochemical performance, with a high initial discharge capacity of 1571.3 mAh g−1 at 0.1C and a low decay of 0.026% per cycle after 500 cycles at 2C. This work provides new insight for designing high-performance electrocatalytic materials for Li-S batteries.

Narrow-Spectrum WSe2 Nanosheet Antibiotics for the Therapy of Multi-Drug Resistant Bacterial Infections

Abuse of broad-spectrum antibiotics not only causes intestinal microbial imbalance but also emerges bacteria resistant to multiple drugs. Therefore, it is an urgent task to develop narrow-spectrum antibiotics and new bactericidal mechanisms to overcome the limitations of broad-spectrum antibiotics for the effective therapy of bacterial infections. Herein, we present ultrathin WSe2 and MoSe2 nanosheets exfoliated and functionalized with poly(acrylic acid) (PAA-WSe2 and PAA-MoSe2) in an aqueous solution as a narrow-spectrum antibiotic or a species-specific agent, respectively, to treat bacterial infection diseases. PAA-WSe2 nanosheets exhibited bactericidal activity only against gram-positive bacteria including multidrug-resistant S. aureus, whereas PAA-MoSe2 showed selective bactericidal activity against S. aureus only. Moreover, PAA-WSe2 accelerated the oxidation-reduction reaction mediated by lipoteichoic acid, a component of the cell membrane of gram-positive bacteria, producing Se4+ for antibacterial activity. Subsequently, the PAA-WSe2 nanosheets induced depolarization and disruption of the bacteria-cytoplasmic membrane for the complete eradication of gram-positive bacteria. PAA-TMD nanosheets, including PAA-WSe2 and PAA-MoSe2, also exhibited outstanding biocompatibility against normal cells and high hemocompatibility with red blood cells. Finally, PAA-WSe2 nanosheets effectively eradicated S. aureus infecting the wounds of mice, showing excellent therapeutic effects in vivo. These results suggest that PAA-WSe2 has been developed as a narrow-spectrum antibiotic used for various bacterial infections. Figure 1

Atomic substitution engineering-induced domino synergistic catalysis in Li-S batteries

Atomic substitution engineering is considered as effective strategy to activate the basal plane of molybdenum disulfide (MoS2) which has been demonstrated effective catalytic cathode in lithium-sulfur (Li-S) batteries. Rationally designing atomic substitution structure is vital to figure out the origin of catalytic activity in doped-MoS2 based catalytic cathodes. Herein, an “adjacent period, adjacent group” atomic substitution engineering is constructed to investigate the role of foreign atoms in sulfur redox reaction, and reveal the origin of catalytic activity. Theoretical calculations reveal that the real active sites are the S atoms adjacent to the doped atoms. It has been demonstrated that Nb atomic substitution acts as an initiator to trigger a “Domino Effect” of activating the S sites, enhancing the adsorption ability, facilitating the conversion reaction of sulfur species, and accelerating the Li+ diffusion. Enlightened by the theoretical guidance, Nb-doped MoS2 ultrathin nanosheets assembled hollow nanotubes (Mo1-xNbxS2 HNTs) are fabricated as efficient “adsorption-conversion” sulfur hosts, which exhibit high initial discharge capacities (1163 mAh g−1 at 0.2 C, 971 mAh g−1 at 0.5 C). An initial capacity of 613 mAh g−1 could be achieved under high sulfur loading (3.13 mg cm−2) and lean electrolyte (5.6 μL mg−1). This work provides pivotal guidance to design highly efficient catalytic cathodes for advanced Li-S batteries.

Interface-Engineered MoSe2-Co9S8 Nanoheterostructures with Enhanced Charge Storage Performance for Supercapacitor Application.

Cobalt-based chalcogenides have emerged as fascinating materials for supercapacitor applications owing to the presence of various mixed valance oxidation states in their structure along with rich electrochemical properties. However, their limited stability and cyclic performance hinder their viability for practical use in supercapacitors. Herein, a facile hot injection colloidal route is demonstrated to design MoSe2-Co9S8 nanoheterostructures (NHSs), which entails the epitaxial growth of Co9S8 nanoparticles (NPs) over the basal planes of ultrathin MoSe2 nanosheets (NSs). The interfacial engineering of the basal planes of MoSe2 NSs with Co9S8 NPs regulates the electronic properties and defects at the interfaces and increases the overall specific surface area and conductivity. As a result, MoSe2-Co9S8 NHSs electrode unveils a substantially higher specific capacitance of 910.5 F g-1 at 1 A g-1current density surpassing their individual counterparts. In addition, it demonstrates worthy solidity, retaining ≈90% of its capacitance and coulombic efficiency of 93.3% after 10,000 charge-discharge cycles at a high charge-discharge current density of 15 A g-1. As a proof-of-concept, coin cells are fabricated using MoSe2-Co9S8 NHSs which show 93% Coulomb efficiency and 86% capacitance retention. This study would pave the way for designing transition metal dichalcogenides (TMDs) - derived NHSs with superior capacitive properties.

Ultrathin 2D/2D MoS2/Bi2WO6 S-scheme heterojunction for boosting photocatalytic degradation of ciprofloxacin

A series of 2D/2D MoS2/Bi2WO6 S-scheme heterojunctions consisting of ultrathin MoS2 nanosheets (MS, 1.6 nm) and ultrathin Bi2WO6 nanosheets (BWO, 1.5 nm) were developed for photocatalytic degradation of ciprofloxacin. The samples with 5 % mass ratio of MS (5 %MS/BWO) exhibits the almost complete degradation of ciprofloxacin (≈100 %) under visible light. It is evidenced that the formation of S-scheme heterojunction with close interfacial interaction facilitates the photoinduced carrier separation and the generation of surface acid sites. The activation of ciprofloxacin molecules is realized through the coordinately interaction of C-N and C=O with the surface W sites. Moreover, the OVs in BWO side is a convenient pathway for activated of O2, embodying in the generation of •O2− and •OH under visible light over photocatalyst. Such an association of charge transfer mechanism with coordination activation shows the enhanced photocatalytic performance toward ciprofloxacin. This work provides a motivation which designs an S-scheme heterojunction photocatalyst with the ability to activate the specific group in molecules to comprehend the degradation of antibiotics.

In Situ Fe/Co/B Codoped MoS2 Ultrathin Nanosheets Enable Efficient Electrocatalytic Nitrogen Reduction.

The development of sustainable and effective electrochemical nitrogen fixation catalysts is crucial for the mitigation of the terrible energy consumption resulting from the Haber-Bosch process. Molybdenum disulfide (MoS2) exhibits promise toward nitrogen reduction reaction (NRR) on account of its similar structure to natural nitrogenases MoFe-co but still undergoes serious challenges with unsatisfactory catalytic performance resulted from limited active sites, conductivity, and selectivity. In this work, Fe/Co/B codoped MoS2 ultrathin nanosheets are synthesized and verified as excellent NRR catalysts with high activity, selectivity, and durability. The FeCoB-MoS2 demonstrates a high ammonia yield of 36.99 μg h-1 mgcat-1 at -0.15 V vs RHE and Faraday efficiency (FE) of 30.65% at -0.10 V vs RHE in 0.1 M HCl. The experimental results and the density functional theory (DFT) calculations emphasize that codoping of Fe, Co, and B into MoS2 synergistically enhances its conductivity and optimizes the electronic structure of the catalyst, which significantly improves the electrocatalytic ammonia synthesis performance. This work broadens the potential and enlightens the strategy for designing efficient electrocatalysts in the NRR field.

Synthesis of MoS2/Co9S8@CoNC by impregnation and calcination for highly efficient lithium-O2 batteries

The activity of electro-catalyst on oxygen cathode is a key factor affecting the property of lithium-O2 batteries (LOBs). In this work, zeolitic imidazolate framework (ZIF–67) was impregnated in (NH4)2MoS4 solution, and then through centrifugation and calcination, nano-MoS2 and Co9S8 were grown on the surface of CoNC skeleton. The composite has mesoporous structure and abundant active groups such as Co, Co9S8, Co-N bond, Mo-N bond and active edges of MoS2 with sulfur vacancies. The coating of ultra-thin MoS2 nanosheets can improve the stability of CoNC skeleton. The Mo component induces the transformation of amorphous carbon of CoNC to graphitic carbon during calcination in order to improve conductivity of the composite. This study shows that MoS2/Co9S8@CoNC is good electro-catalyst for O2 reduction and evolution reactions (ORR/OER). The LOBs with MoS2/Co9S8@CoNC oxygen cathode show high specific discharge capacity (18162 mA h g−1) and good cycle performance (304 cycles).

Spatially confined synthesis of large-sized MoS2 nanosheets in molten KSCN toward efficient hydrogen evolution

Low-temperature KSCN molten salt is a promising technique to synthesize defect-rich MoS2 catalysts for hydrogen evolution reaction (HER). However, owing to the fast ion diffusion rate for rapid crystal growth, the resultant catalysts show a morphology of microsphere, which aggregates from MoS2 nanosheets, to suppress the catalytic performance. In this work, large-sized few-layer MoS2 nanosheets are synthesized via a spatial confinement strategy by adding inert NaCl into the KSCN molten salt. With the NaCl spacer to physically block the long-distance ion diffusion and isolate the chemical reaction, the MoS2 nucleation and subsequent crystal growth could be controlled, guiding the nanosheets to grow along the narrow gap between the NaCl crystals to avoid aggregation. As a result, ultrathin MoS2 nanosheets with a large geometry size are constructed. Profiting from the architecture to expose active sites and boost charge transfer kinetics, the large-sized few-layer MoS2 nanosheets exhibit an impressive HER performance, showing a small η 10 of 160 mV and a low Tafel slope of 53 mV dec−1 with excellent stability. This work provides not only an efficient HER catalyst but also a facile spatial confinement technique to design and synthesize a large spectrum of transition metal sulfides for broad uses.

RGO@MoS2 as the host-separator modifier with efficient polysulfides trapping and fast Li+ diffusion for lithium-sulfur batteries

Lithium sulfur battery is widely regarded as the most promising next generation energy storage systems because of its high specific energy (2600 Wh kg−1). However，its commercial application is still limited by numerous challenges, including the insulation of charging/discharging products sulfur and Li2S2/Li2S, as well as the "shuttle effect" triggered by the soluble polysulfides. Herein, we report that a functional separator modified by a rGO@MOS2 composites comprising ultrathin MoS2 nanosheets in-situ growth on the surface of reduced graphene oxide (rGO). This composite boasts -an abundant mesoporous structure and large specific surface area can effectively adsorb lithium polysulfides (LiPSs). Additionally, the introduction of high conductive rGO and ultrathin MoS2 nanosheets with rich edge active sites can accelerate the catalytic transformation reaction from LiPSs to Li2S2/Li2S, thus inhibiting the "shuttle effect". In comparison to Li-S batteries without rGO@MoS2 composites, batteries equipped with the functional separator exhibit an impressive initial discharge capacity of 1125.4 mAh g−1 at 1 C, and retain at 910.4 mAh g−1 after 200 cycles, with a low capacity decay rate of 0.09 % per cycle, indicating excellent cyclic stability. Moreover, the areal capacity of the electrode with high sulfur loading mass of 4.1 mg cm−2 is 4.1 mAh cm−2, approaching the practical application standard at a current density of 0.1 C.

Directionally charging d-orbital electron of Mo2C MXene via in-situ coupled MoSe2 nanosheets for exceptional photocatalytic H2 generation

Mo2C MXene as a promising noble-metal-free cocatalyst has attracted considerable attention in the domain of photocatalytic H2 evolution due to its unique 2D layered structure, outstanding metallic conductivity, and Pt-like d-band electronic structure. However, the plentiful −F terminal groups with high electronegativity of Mo2C MXene (referred as Mo2CFx) owing to the residue of F-containing etchants lead to strong interaction between active Mo sites and adsorbed atomic H (Mo-Had bond), thereby decreasing the H2-evolution activity of Mo2CFx. In this work, a directionally charging d-orbital electron strategy of Mo2CFx-MoSe2 heterojunction via increasing the antibonding-orbital occupancy state of Mo to weaken Mo-Had bond in Mo2CFx is presented for the enhanced H2-generation performance. Herein, the ultrathin MoSe2 nanosheets are first vertically grown on the Mo2CFx surface via an in-situ selenization route to form Mo2CFx-MoSe2 heterojunction, and subsequently combined with the TiO2 to prepare the TiO2/Mo2CFx-MoSe2 through an ultrasonic-assisted method. The H2-evolution activity test indicates that the optimal TiO2/Mo2CFx-MoSe2 photocatalyst possesses an exceptional H2-evolution rate (427.66 μmol h−1 g−1), which is 38.98 and 1.94 folds higher than that of the TiO2 and TiO2/Mo2CFx, respectively. The experimental data and density functional theory (DFT) calculations substantiate that the generation of Mo2CFx-MoSe2 heterojunction can weaken the Mo-Had bond by electron transfer from MoSe2 to Mo2CFx for charging d-orbital electrons, accordingly promoting the photocatalytic H2-evolution efficiency of TiO2. This study highlights the optimization of Mo-Had bond by constructing Mo2CFx-based heterojunction to realize high-efficient photocatalytic H2 evolution.

Pd nanoflakes epitaxially grown on defect MoS2 nanosheets for enhanced nitroarenes hydrogenation to anilines

Hydrogenation of nitroarenes to anilines under mild conditions is attractive from both theoretical and practical viewpoints. Here, high-performance catalyst with layered Pd nanoparticles epitaxially growing on ultrathin MoS2 nanosheets (Pd/MoS2) were prepared. It shows surprisingly high catalytic activity, selectivity and stability for hydrogenation of various nitroarenes to corresponding anilines; the turnover frequency is one or two magnitudes higher than conventional Pd-based catalysts. Surface sulfur vacancies are formed on MoS2 nanosheets with low formation energy barrier. These S vacancies provide efficient positions for adsorbing Pd atoms, which enables facile cleavage of N–O bond as result of strong interfacial electron interaction that decreases activation energy by 0.41 eV in comparison with conventional Pd catalysts. In situ spectroscopy and DFT calculation results reveal a dual-site mechanism, in which surface Pd sites adsorb and dissociate H2 into active H*, and then readily reacts with nearby activated nitroarene to form aniline on interfacial Pd-MoS2 sites.

CdS/ZnS core–shell nanorod heterostructures co-deposited with ultrathin MoS2 cocatalyst for competent hydrogen evolution under visible-light irradiation

Hydrogen generation via semiconductor photocatalysts has gained significant attention as a sustainable fuel generation process. To demonstrate the performance of nanoscale core–shell heterostructure in photocatalytic hydrogen production, we have fabricated CdS nanorods coated with ZnS photocatalyst via wet-chemical reaction followed by deposition of ultrathin MoS2 nanosheets by photo reduction process. The effect of ZnS content and suitable amount of MoS2 loading over the visible-light induced photocatalytic hydrogen evolution was examined in Na2S and Na2SO3 aqueous solutions. Interestingly, it is apparent that a close connection (or heterojunction) between CdS and ZnS is believed to easily tunnel the charge carriers to the surplus surface states, making its electrons and holes energetically favourable to transfer from ZnS to MoS2 for photocatalytic reactions and subsequently, enhances the H2 evolution activity in CdS/ZnS type I core–shell heterostructures. The optimal MoS2 concentration is resolved to be 7 mol% and the subsequent visible-light induced H2 generation rate was 13589 μmol h−1g−1, which is 19 and 158 fold higher than pristine CdS and ZnS respectively. The probable photocatalytic mechanism of CdS/ZnS type I core–shell heterostructure with MoS2 cocatalyst is proposed. Our inexpensive and convenient preparation strategy may offer novel prospects in the engineering of desirable nanoheterostructures with better performance.

Sulfur Vacancies and 1T Phase-Rich MoS2 Nanosheets as an Artificial Solid Electrolyte Interphase for 400Wh kg-1 Lithium Metal Batteries.

Constructing large-area artificial solid electrolyte interphase (SEI) to suppress Li dendrites growth and electrolyte consumption is essential for high-energy-density Li metal batteries (LMBs). Herein, chemically exfoliated ultrathin MoS2 nanosheets (EMoS2) as an artificial SEI are scalable transfer-printed on Li-anode (EMoS2@Li). The EMoS2 with a large amount of sulfur vacancies and 1T phase-rich acts as a lithiophilic interfacial ion-transport skin to reduce the Li nucleation overpotential and regulate Li+ flux. With favorable Young's modulus and homogeneous continuous layered structure, the proposed EMoS2@Li effectively suppresses the growth of Li dendrites and repeat breaking/reforming of the SEI. As a result, the assembled EMoS2@Li||LiFePO4 and EMoS2@Li||LiNi0.8Co0.1Mn0.1O2 batteries demonstrate high-capacity retention of 93.5% and 92% after 1000 cycles and 300 cycles, respectively, at ultrahigh cathode loading of 20mg cm-2. Ultrasonic transmission technology confirms the admirable ability of EMoS2@Li to inhibit Li dendrites in practical pouch batteries. Remarkably, the Ah-class EMoS2@Li||LiNi0.8Co0.1Mn0.1O2 pouch battery exhibits an energy density of 403 Wh kg-1 over 100 cycles with the low negative/positive capacity ratio of 1.8 and electrolyte/capacity ratio of 2.1 g Ah-1. The strategy of constructing an artificial SEI by sulfur vacancies-rich and 1T phase-rich ultrathin MoS2 nanosheets provides new guidance to realize high-energy-density LMBs with long cycling stability.

Interfacial coupling of NiSe in heterostructures promotes electrocatalytic hydrolysis of MoS2.

Molybdenum sulfide (MoS2) has attracted much attention as a potential catalyst for the oxygen evolution reaction (OER), but its unique low activity and low edge active centers limit its electrocatalytic activity. In this study, catalysts were prepared by growing NiSe nanoclusters in situ onto MoS2 substrates via electrodeposition; ultrathin MoS2 nanosheets and NiSe nanoclusters were cross-linked with each other to form a unique three-dimensional rosette structure; and MoS2@NiSe catalysts were successfully synthesised, which significantly improved bifunctional catalytic performance. The synthesised MoS2@NiSe catalysts exhibited good electrochemical performance: overpotentials required to satisfy the HER and OER processes at a current density of 10 mA cm-2 in 1 M KOH were 80 mV and 254 mV, respectively. When applied as a cathode and anode to assemble a bifunctional electrode system, the MoS2@NiSe||MoS2@NiSe electrolytic cell system required only 1.54 V to achieve 10 mA cm-2 in an alkaline electrolyte, which exceeded the value of most of the bifunctional catalysts reported in the literature to date. In addition, the catalyst maintained good surface structure and catalytic performance after a 24 h stability test. This study provides a new idea for the improvement and design of MoS2-based bifunctional catalysts and provides an important reference for research in the field of clean energy.

Crystallinity and interfacial Mo–N–C bond engineered MoS2 embedded graphitic nitrogen doped carbon hollow sphere for enhanced HER activity

To restrain fossil fuel depletion, the need of the hour is the development of efficient, durable, and non-precious electrocatalysts for the hydrogen evolution reaction (HER). The hierarchical nanostructure consisting of transition metal dichalcogenides and graphitic heteroatom-doped carbon with an abundant interfacial M–N–C catalytic site is highly demanding for electrolytic applications. Herein, we report crystallinity-engineered ultrathin MoS2 nanosheets hierarchy over nitrogen-doped graphitic carbon (NC) hollow spheres as a promising material for HER. The well optimized NC@MoS2 demonstrates superior HER activity with a low onset overpotential of 9 mV and an overpotential of 145 mV at a current density of −10 mA cm−2. It exhibits low Tafel slope of 39 mV dec−1 and excellent chronoamperometric stability. Superior HER activity originates from interfacial Mo–N–C bonds. Density functional theory (DFT) calculations unveil that Mo–N–C bonds between MoS2 and NC matrix ease electronic transportation and further diminish Gibbs free energy for HER.

‘MoS2-coated nitrogen/oxygen co-doped carbon nanocages composite as active material for supercapacitor electrodes

Nitrogen/oxygen co-doped carbon nanocages (NOCN) have been deemed as promising materials in renewable energy-storage applications. Herein, we report a facile one-pot hydrothermal approach for formation of three-dimensional (3D) flower-like MoS2 nanoflakes/NOCN composite (MoS2@NOCN) with excellent storage properties as anode for supercapacitor. As a result, ultrathin MoS2 nanosheets were vertically grown onto the surface of NOCN, which can prevent sheet aggregation and provide a rapid pathway for electron transfer. The as-prepared MoS2@NOCN composites were characterized by electrochemical measurements to demonstrate the supercapacitor performance. The results indicate that MoS2@NOCN-3 exhibited a high specific capacitance (240.8 F g−1 at 0.5 A g−1) and excellent rate performance (approximately 46.4 % from 1 A g−1 to 10 A g−1). The as-obtained composites demonstrated their potential applications in supercapacitor electrode materials.

Photodeposition of highly dispersed MoS2 nanosheets on CdS nanorods with enhanced photocatalytic activity for reduction of p-nitroaniline to p-phenylenediamine

So far, the significant effect of different assembly methods on the microstructures and photocatalytic properties of MoS2/CdS nanocomposite photocatalysts has rarely been reported. In the study, single-crystalline CdS nanorods (NRs) were prepared by a solvothermal method. MoS2 cocatalyst was decorated on the CdS NRs to obtain MoS2/CdS-PD and MoS2/CdS-HT photocatalysts by an in situ photodeposition (PD) technique and a hydrothermal (HT) method, respectively. Under visible light irradiation, the photocatalytic activity of MoS2/CdS-PD and MoS2/CdS-HT for reduction of p-nitroaniline (p-NA) to p-phenylenediamine (p-PDA) was comparatively studied. Results indicate: i) When MoS2 was attached on CdS NRs by the in situ PD, ultrathin MoS2 nanosheets could be uniformly and tightly tethered to CdS NRs to form core-shell MoS2/CdS-PD composite, whereas MoS2 nanosheets were aggregated to form stacked multilayered structure and loosely coupled to CdS NRs to produce non-core-shell MoS2/CdS-HT by the HT method. ii) MoS2/CdS-PD exhibits higher photocatalytic efficiency for p-NA reduction than MoS2/CdS-HT, which can be ascribed to the fact that the interfacial contact between MoS2 and CdS is more intimate and the electron transfer from CdS to MoS2 is more efficient in MoS2/CdS-PD than that in MoS2/CdS-HT.

Fabrication of high-performance symmetric pseudocapacitor by synthesizing ionic liquid-modified graphene/MoS2 NS binary electrode

The combination of graphene with metal sulfides has always been getting attention from researchers due to the compatibility in their two-dimensional structure with active sites on their edges and their exceptional optical, magnetic, and physiochemical properties. Herein, we synthesize highly efficient pseudocapacitive electrode material using ionic liquid-modified graphene (IL-rGO) and ultrathin MoS2 nanosheets (MoS2 NS). The electrochemical properties of graphene were tuned by modifying its surface with green solvents such as ionic liquids. Modification of the graphene surface with IL increased the number of active sites at the edges, and provided a more compact arrangement to the graphene layers which enabled them to accommodate MoS2 NSs between them. Among the synthesized binary electrodes, 1.5 g IL-modified rGO loaded with 15 wt% of MoS2 NS electrode, the PIRM15 binary electrode, exhibits a high specific capacitance of 955 F/g. TEM micrographs of the PIRM15 electrode delineated the intercalation of MoS2 NSs between the graphene layers. The PIRM15 electrode displayed 93.7 % of pseudocapacitance and 6.7 % electrical double-layer capacitance. The symmetric pseudocapacitor integrated with the PIRM15 binary electrode possesses 97 % capacitance retention and 87 % coulombic efficiency at 0.008 A. The pseudocapacitor's calculated energy and power densities are 25 Wh/kg and 3333 W/kg at a current of 0.003 A and 0.05 A, respectively.

Non-covalent interaction of atomically dispersed dual-site catalysts featuring Co and Ni nascent pair sites for efficient electrocatalytic overall water splitting

The scarcity of highly effective and economical catalysts is a major impediment to the widespread adoption of electrochemical water splitting for the generation of hydrogen. MoS2, a low-cost candidate, suffers from inefficient catalytic activity. Nonetheless, a captivating strategy has emerged, which involves the engineering of heteroatom doping to enhance electrochemical proficiency. This investigation demonstrates a successful implementation of the strategy by combining ultrathin MoS2 nanosheets with Co and Ni dual single multi-atoms (DSMAs) grown directly on 2D N-doped carbon nanosheets (CoNi-MoS2/NCNs) for the purpose of improving hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). With the aid of a dual-atom doped bifunctional electrocatalyst, effective water splitting has been achieved across a broad pH range in electrolytes. The double doping of Co and Ni strengthens their interactions, thereby altering the electromagnetic composition of the host MoS2 and ultimately leading to improved electrocatalytic activity. Additionally, the synergistic effect between NCNs and MoS2 nanosheets provided efficient electron transport channels for ions and an ample surface area with open voids for ion diffusion. Consequently, the CoNi-MoS2/NCNs catalysts demonstrated exceptional stability and activity, producing low degree overpotentials of 180.5, 124.9, and 196.4 mV for HER and 200, 203, and 207 mV for OER in neutral, alkaline, and acidic mediums, respectively, while also exhibiting outstanding overall water-splitting performance, durability, and stability when used as an electrolyzer at universal pH.

Engineering Double Sulfur-Vacancy in CoS1.097@MoS2 Core-Shell Heterojunctions for Hydrogen Evolution in a Wide pH Range.

Heterostructured nanomaterials have arisen as electrocatalysts with great potential for hydrogen evolution reaction (HER), considering their superiority in integrating different active components but are plagued by their insufficient active site density in a wide pH range. In this report, double sulfur-vacancy-decorated CoS1.097@MoS2 core-shell heterojunctions are designed, which contain a primary structure of hollow CoS1.097 nanocubes and a secondary structure of ultrathin MoS2 nanosheets. Taking advantage of the core-shell type heterointerfaces and double sulfur-vacancy, the CoS1.097@MoS2 catalyst exhibits pH-universal HER performance, achieving the overpotentials at 10 mA cm-2 of 190, 139, and 220 mV in 0.5 M H2SO4, 1.0 M KOH, and 1.0 M PBS, respectively. Systematic theoretical results show that the double sulfur-vacancy can endow the CoS1.097@MoS2 core-shell heterojunctions with promoted electron/mass transfer and enhanced reactive kinetics, thus boosting HER performance. This work clearly demonstrates an indispensable role of double sulfur-vacancy in enhancing the electrocatalytic HER performance of core-shell type heterojunctions under a wide pH operating condition.