Interface electronic engineering of molybdenum sulfide/MXene hybrids for highly efficient biomimetic sensors

Interface regulation plays a key role in the electrochemical performance for biosensors.By controlling the interfacial interaction,the electronic structure of active species can be adjusted effectively at micro and nano-level,which results in the optimal reaction energy barrier.Herein,we propose an interface electronic engineering scheme to design a strongly coupled 1T phase molybdenum sulfide(1T-MoS2)/MXene hybrids for constructing an efficient electrocatalytic biomimetic sensor.The local electronic and atomic structures of the 1T-MoS2/Ti3C2TX are comprehensively studied by synchrotron radiation-based X-ray photoelectron spectroscopy(XPS),as well as X-ray absorption spectroscopy(XAS)at atomic level.Experiments and theoretical calculations show that there are interfacial stresses,atomic defects and adjustable bond-length between MoS2/MXene nanosheets,which can significantly promote biomolecular adsorption and rapid electron transfer to achieve excellent electrochemical activity and reaction kinetics.The 1T-MoS2/Ti3C2TX modified electrode shows ultra high sensitivity of 1.198μA/μM for dopamine detection with low limit of 0.05μM.We anticipate that the interface electronic engineering investigation could provide a basic idea for guiding the exploration of advanced biosensors with high sensitivity and low detection limit.

Amorphous molybdenum sulfide and its Mo-S motifs:Structural characteristics,synthetic strategies,and comprehensive applications

Amorphous materials are one kind of nonequilibrium materials and have become one of the most active research fields.Compared with crystalline solids,the theory of amorphous materials is still in infancy because their characteristic of atomic arrangement is more like liquid and has no long-range periodicity.Recently,as the representative of amorphous materials,amorphous molybdenum sulfide(a-MoS_(x))with unique physical and chemical properties has been studied extensively.However,considerable debate surrounds the structure–property relationships of a-MoS_(x)owing to its diverse Mo-S motifs.Herein,we summarize recent discoveries and research results regarding a-MoS_(x),whose structural characteristics,synthetic strategies,formation criteria,and comprehensive applications are discussed in detail.Finally,this review is ended with our personal insights and critical outlooks over the development of a-MoS_(x).

Nitrogen incorporated nickel molybdenum sulfide as efficient electrocatalyst for overall water splitting

Developing bifunctional electrocatalysts with improved efficiency and stability in overall water splitting is of extreme importance for renewable energy utilization.In this work,an in situ N doping strategy was demonstrate to boost the efficiency and stability of nickel molybdenum sulfide both in electrocatalytic hydrogen evolution reaction and oxygen evolution reaction.Experimental and theoretical results indicate that such modification offers enriched active sites for electrochemical reaction,and further increases the kinetic driven force of water electrolysis.As a result,the N–NiMoS electrode exhibits a remarkably improved performance with rather low potential of 1.54 V to offer a current density of 10 mA cm;for overall water splitting,which is 130 mV decrease than that of pristine one.In addition,impressive electrochemical stability also reveals a 76.6%preservation of initial current density after 100 h test,which is superior than that of pristine one after 25 h test.Therefore,the potential to enhance the performance of electrocatalysts by as-proposed route promises a valuable way to develop efficient catalysts with enhanced property for electrochemical applications.

Efficient solar fuel production enabled by an iodide oxidation reaction on atomic layer deposited MoS_(2)

Oxygen evolution reaction(OER)as a half-anodic reaction of water splitting hinders the overall reaction efficiency owing to its thermodynamic and kinetic limitations.Iodide oxidation reaction(IOR)with low thermodynamic barrier and rapid reaction kinetics is a promising alternative to the OER.Herein,we present a molybdenum disulfide(MoS_(2))electrocatalyst for a high-efficiency and remarkably durable anode enabling IOR.MoS_(2)nanosheets deposited on a porous carbon paper via atomic layer deposition show an IOR current density of 10 mA cm^(–2)at an anodic potential of 0.63 V with respect to the reversible hydrogen electrode owing to the porous substrate as well as the intrinsic iodide oxidation capability of MoS_(2)as confirmed by theoretical calculations.The lower positive potential applied to the MoS_(2)-based heterostructure during IOR electrocatalysis prevents deterioration of the active sites on MoS_(2),resulting in exceptional durability of 200 h.Subsequently,we fabricate a two-electrode system comprising a MoS_(2)anode for IOR combined with a commercial Pt@C catalyst cathode for hydrogen evolution reaction.Moreover,the photovoltaic–electrochemical hydrogen production device comprising this electrolyzer and a single perovskite photovoltaic cell shows a record-high current density of 21 mA cm^(–2)at 1 sun under unbiased conditions.

Synergistically coupling of Ni–Fe LDH arrays with hollow Co–Mo sulfide nanotriangles for highly efficient overall water splitting

Developing bifunctional catalysts that can catalyze both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)is pivotal to commercializing large-scale water splitting.Herein,a novel hollow nanotriangle composed of NiFe LDH-CoMoS_(x) heterojunction(H-CMSx@NiFe LDH)is proposed as a highly efficient bifunctional electrocatalyst for both OER and HER.To fabricate a heterojunction system,ultra-thin nickel–iron layered double hydroxide(NiFe LDH)nanosheets are uniformly electrodeposited onto a metal–organic framework-derived hollow CoMoS_(x) nanotriangle.The strong coupling of CoMoS_(x) and NiFe LDH catalysts forms the intimate heterojunction interfaces to facilitate interfacial charge transfer,which is favorable to enhance the bifunctional catalytic activity.Moreover,the large void of CoMoS_(x) nanotriangles and interconnected ultra-thin NiFe LDH nanosheets result in good electrolyte penetration and gas release.Therefore,the as-prepared H-CMSx@NiFe LDH on nickel foam(NF)exhibits an impressive catalytic activity and durability for OER and HER activities,delivering a current density of 100 mA·cm^(−2) at the small overpotentials of 214 and 299 mV in OER and HER,respectively.Meanwhile,H-CMSx@NiFe LDH/NF proves to be an effective electrode for an alkaline electrolyzer,as a voltage of only 1.99 V is enough to achieve a current density voltage of only 1.99 V is enough to achieve a current density of 400 mA·cm^(−2) with no degradation in performance over 50 h.

Interfacial engineering of heterostructured carbon-supported molybdenum cobalt sulfides for efficient overall water splitting

Constructing hetero-structured catalyst is promising but still challenging to achieve overall water splitting for hydrogen production with high efficiency.Herein,we developed a sulfide-based MoS_(2)/Co_(l-x)S@C hetero-structure for highly efficient electrochemical hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).The carbon derived from the filter paper acts as a conducting carrier to ensure adequate exposure of the active sites guaranteed with improved catalytic stability.The unique hierarchical nano-sheets facilitate the charge and ion transfer by shortening the diffusion path during electro-catalysis.Meanwhile,the robust hetero-interfaces in MoS_(2)/Co_(1-x)S@C can expose rich electrochemical active sites and facilitate the charge transfer,which further cooperates synergistically toward electro-catalytic reactions.Consequently,the optimal MoS_(2)/Co_(1-x)S@C hetero-structures present small over-potentials toward HER(135 mV@10 mA·cm^(-2))and OER(230 mV@10 mA·cm^(-2)).The MoS_(2)/Co_(1-x)S@C electrolyzer requires an ultralow voltage of 1.6 V at the current density of 10 mA·cm^(-2)with excellent durability,outperforming the state-of-the-art electro-catalysts.This work sheds light on the design of the hetero-structured catalysts with interfacial engineering toward large-scale water splitting.

MoS_3 loaded TiO_2 nanoplates for photocatalytic water and carbon dioxide reduction

Photocatalytic water splitting and carbon dioxide reduction provide us clean and sustainable energy resources. The carbon dioxide reduction is also the redemption of the greenhouse effect. MoS_3/TiO_2 photocatalysts based on TiO_2 nanoplates have been synthesized via a hydrothermal acidification route for water and carbon dioxide reduction reactions. This facile approach generates well dispersed Mo S3 with low crystallinity on the surface of TiO_2 nanoplates. The as-synthesized MoS_3/TiO_2 photocatalyst showed considerable activity for both water reduction and carbon dioxide reduction. The thermal treatment effects of TiO_2 , the loading percentage of MoS_3 and the crystalline phase of TiO_2 have been investigated towards the photocatalytic performance. TiO_2 nanoplate synthesized through hydrothermal reaction with the presence of HF acid is an ideal semiconductor material for the loading of MoS_3 for photocatalytic water and carbon dioxide reduction simultaneously in EDTA sacrificial solution.

Confined synthesis of MoS_(2) with rich co-doped edges for enhanced hydrogen evolution performance

Activating MoS_(2) with atomic metal doping is promising to harvest desirable Pt-matched hydrogen evolution reaction(HER)catalytic performance.Herein,we developed an efficient method to access edgerich lattice-distorted MoS_(2) for highly efficient HER via in-situ sulphuration of atomic Co/Mo species that were well-dispersed in a formamide-derived N-doped carbonaceous(f-NC)substrate.Apart from others,pre-embedding Co/Mo species in f-NC controls the release of metal sources upon annealing in S vapor,grafting the as-made MoS_(2) with merits of short-range crystallinity,distorted lattices,rich defects,and more edges exposed.The content of atomic Co species embedded in MoS_(2) reaches up to 2.85 at.%,and its atomic dispersion has been systematically confirmed by using XRD,HRTEM,XPS,and XAS characterizations.The Co-doped MoS_(2) sample exhibits excellent HER activity,achieving overpotentials of 67 and155 m V at j=10 m A cm^(-2) in 1.0 M KOH and 0.5 M H_(2)SO_(4),respectively.Density functional theory simulations suggest that,compared with free-doping MoS_(2),the edged Co doping is responsible for the significantly improved HER activity.Our method,in addition to providing reliable Pt-matched HER catalysts,may also inspire the general synthesis of edge-rich metal-doped metal chalcogenide for a wide range of energy conversion applications.

Probing Diverse Disulfur Ligands in the Mo_2S_n^(–/0)(n = 4 ～ 8) Clusters: Structural Evolution and Chemical Bonding

Density functional theory(DFT) and coupled cluster theory(CCSD(T)) calculations were employed to investigate the geometric and electronic structures of a range of dinuclear molybdenum sulfide clusters, Mo_2S_n~– and Mo_2S_n(n = 4～8). The results showed that the sulfur atoms tended to occupy the terminal sites of the clusters continuously in the process of sequential sulfidation. After the oxidation state of Mo atoms reached the maximum of +6, diverse disulfur ligands emerged in the sulfur-rich Mo_2S_n^(–/0)(n = 7, 8) clusters. The driving forces of removing a sulfur atom from different S ligands in Mo_2S_n^(–/0)(n = 4～8) clusters, especially from those disulfur units, were evaluated. The corresponding order may provide insight into the pretreatment of fresh MoS_2 catalysts. Vertical detachment energies(VDEs) were predicted according to the Generalized Koopmans' theorem, and then the photoelectron spectra(PES) were simulated. Molecular orbital and spin density values were analyzed to elucidate the chemical bonding and the evolutionary behavior in the dinuclear molybdenum sulfide clusters.

"Small amount for multiple times" of H_(2)O_(2) feeding way in MoS_(2)-Fex heterogeneous fenton for enhancing sulfadiazine degradation

In recent years, MoS_(2) catalyzed/cocatalyzed Fenton/Fenton-like systems have attracted wide attention in the field of pollution control, but there are few studies on the effect of H_(2)O_(2) feeding way on the whole Fenton process. Here, we report a new type of composite catalyst (MoS_(2)-Fe_(x)) prepared in a simple way with highly dispersed iron to provide more active sites. MoS_(2)-Fe_(x) was proved to possess selectivity for singlet oxygen (^(1)O_(2)) in effectively degrading sulfadiazine with a wide pH adaptability (4.0~10.0). Importantly, the mechanism of the interaction between H_(2)O_(2) and MoS_(2) on the Fenton reaction activity was revealed through the combination of experiment and density functional theory (DFT) calculations. Compared to the traditional “a large amount for one time” feeding way of H_(2)O_(2), the “small amount for multiple times” of H_(2)O_(2) feeding way can increase the degradation rate of sulfadiazine from 36.9% to 91.1% in the MoS_(2)-Fe_(x) heterogeneous Fenton system. It is demonstrated that the “small amount for multiple times” of H_(2)O_(2) feeding way can reduce the side reaction of decomposition of H_(2)O_(2) by MoS_(2) and effectively improve the utilization rate of H_(2)O_(2) and the stability of MoS_(2)-Fe_(x). Compared with Fe_(2)O_(3)^(-)based Fenton system, MoS_(2)-Fe_(x) can significantly save the amount of H_(2)O_(2). Compared with nano-iron powder, the formation of iron sludge in MoS_(2)-Fe_(x) system was significantly reduced. Furthermore, long-term degradation test showed that the MoS_(2)-Fe75/H_(2)O_(2) system could maintain the effectiveness of degrading organic pollutants for 10 days (or even longer). This study has a guiding significance for the large-scale treatment of industrial wastewater by improved Fenton technology in the future.

Deactivation study of unsupported nano MoS_(2) catalyst

The stability of catalyst is of great importance for a long-term operation.In this paper,the hydrodesulfurization stability and deactivation mechanism of unsupported nano MoS_(2) catalyst was examined with light cycle oil as feedstock under an extreme hydrotreating condition for 160 h.A typical supported catalyst was also studied for comparison purpose.The results show that the activity of nano MoS_(2) can be well maintained after initial deactivation in the first 60 h time-on-stream.Less coke was found on spent nano MoS_(2) than on the spent supported catalyst,though coke deposition is identified as the main cause of deactivation for the nano catalyst.Without acidic supports,only soft coke is formed on the surface of catalyst.Unlike the supported catalyst,decomposition of active phase played a minor role in the deactivation of nano MoS_(2).

Composite separator based on PI film for advanced lithium metal batteries

Lithium(Li) metal batteries have received extensive research focusing on the dendrite growth issue on account of the high chemical activity of Li anode. While, thermal safety, as one of the important security concerns facing the further application, gets little attention. Here, the high-performance polyimide film is successfully developed to enhance the safety margin based on the excellent mechanical strength and heat resistance corresponding to the traditional separator. And, the polyimide film with the Mo S2 coating made by spraying method as the composite separator can not only improve the wettability to the electrolyte, but also in-situ form an artificial layer with the low nucleation barrier for the Li ions. When used in both the coin cell and the pouch cell, all achieve the outstanding cycling stability and the coulombic efficiency. Specially, the in-situ Li ions nucleation behaviors are investigated by optical microscopy in the capillary cell. The electric field intensity at the Li anode surface is also simulated by COMSOL Multiphysics to further elucidate the effect of the coating.

Engineering interfacial band hole extraction on chemical-vapor-deposited MoS 2/CdS core-shell heterojunction photoanode:The junction thickness effects on photoelectrochemical performance

Heterojunction fabrication is a promising strategy that can greatly boost the charge carrier separation and improve the solar-to-hydrogen conversion efficiency of photoelectrochemical(PEC)cells.However,such technology still suffers from limited contact interfaces.In this study,the chemical vapor deposition(CVD)technique was for the first time used to construct the CdS/MoS_(2)heterojunction photoanode with a unique core-shell nanoarchitecture,in which a continuous crystalline MoS_(2)nanosheet layer was grown directly on one-dimensional(1D)oriented CdS nanorods(NRs)in a plane-to-plane stacking fashion.The optimization of junction thickness with adjustable MoS_(2)loading from mono to a few layers was achieved by experimental parameters variation.Systematic characterizations show that the MoS_(2)shell plays a dual role as an optical absorption booster for more photo-exciton generation and a surface passivator of trap states.Meanwhile,the formed heterojunction helps regulate the unidirectional charge migration for a significantly suppressed electron-hole recombination process,which synergistically contributes to higher quantum yield and efficiency.As a result,the optimized CdS/MoS_(2)heterojunction photoanode with 3-layered MoS_(2)wrapping exhibits the highest photocurrent density and photoconversion efficiency,over a two-fold increase,compared to those of pristine CdS and the previously reported CdS/MoS_(2)hetero-junctions.Moreover,due to the rapid hole extraction from CdS and transferred surface oxidation sites,the present CdS/MoS_(2)heterostructure demonstrates better corrosion resistance and higher photostability.The present work is expected to provide a versatile platform for exploiting the CVD technique to develop other MoS_(2)-based heterojunction photoelectrodes with extensive PEC applications.