Large Accessible Surface Area Research Articles

Fluorine-doped carbon dots decorated on iron-cobalt selenide nanosheets as superior electrocatalysts for oxygen evolution in seawater

Developing oxygen evolution reaction (OER) catalysts that can efficiently and stably operate at high current densities in seawater electrolysis is urgently demanded but challenging. In this study, selenium-vacancies-rich iron-cobalt selenide nanosheets (FeCoSe-VSe) decorated with fluorine-doped carbon dots (FCDs) are rationally designed and prepared on nickel foams (NF) through the successive processes of hydrothermal treatment and selenization. Benefiting from the large accessible surface area and abundant active sites provided by FCDs and selenium vacancy defects, as well as the coupled interface between FCDs and FeCoSe-VSe that optimizes the oxygen adsorption energy and accelerates the kinetic process, the FCDs/FeCoSe-VSe/NF composite exhibits excellent OER catalytic activities with a low overpotential of 258 mV at a current density of 200 mA cm−2 in 1 M KOH and a small Tafel slope of 34.7 mV dec–1. In the electrolytes of simulated and natural seawater, the overpotentials of the FCDs/FeCoSe-VSe/NF electrode are slightly higher, measured to be 264 and 297 mV, respectively. More profoundly, the introduction of FCDs enhances the corrosion resistance of the catalyst in alkaline electrolytes, ensuring the long-term stability. This work offers a guidance to improve the electrochemical performances of catalysts for high-efficiency seawater oxidation.

Regulation of extracellular electron transfer by sustained existence of Fe²⁺/Fe³⁺ redox couples on iron oxide-functionalized woody biochar anode surfaces in bioelectrochemical systems

Sluggish extracellular electron transfer between the exoelectrogens and anode interface limits the application of bioelectrochemical systems (BECs) for energy generation. In this study, an innovative anode coated with oxidized biochar and co-functionalized with iron nanoparticles (FBC/Fe2O3) was developed to enhance microbial reactions through tuned physicochemical and electrical properties. The designed anode features a highly porous, heterogeneous structure with a large accessible surface area of 10.141 m²/g, promoting better habitation and metabolism of exoelectrogens. The synergistic effect of iron nanoparticles and oxidized functional groups increased the hydrophilicity of the anode surface, augmenting its affinity for bacterial outer membrane c-cysts and facilitating microbial adhesion at a density of 3.106 × 10⁹ CFU/cm². The iron moieties on the FBC/Fe2O3 electrode surface act as electron mediators, utilizing Fe²⁺/Fe³⁺ redox couples, as evidenced by X-ray photoelectron spectroscopy (XPS) data. This enhancement improved extracellular electron transfer (EET) between bacterial cells and the anode surface, resulting in a faster and bifurcated EET process through both direct transfer via outer membrane c-cysts and mediated transfer via the redox couples of Fe moieties. The assembled double-chamber microbial fuel cell (DC-MFC) with the FBC/Fe2O3 anode achieved a maximum power density of 528.75 mW/m² and a chemical oxygen demand (COD) removal efficiency of 47.5 % within 24 h of operation.

Electroactive Ionic Polymer of Intrinsic Microporosity for High-Performance Capacitive Energy Storage.

Here, an ionic polymer of intrinsic microporosity (PIM) as a high-functioning supercapacitor electrode without the need for conductive additives or binders is reported. The performance of this material is directly related to its large accessible surface area. By comparing electrochemical performance between a porous viologen PIM and a nonporous viologen polymer, it is revealed that the high energy and power density are both due to the ability of ions to rapidly access the ionic PIM. In 0.1m H2SO4 electrolyte, a pseudocapacitve energy of 315 F g-1 is observed, whereas in 0.1m Na2SO4, a capacitive energy density of 250 F g-1 is obtained. In both cases, this capacity is retained over 10000 charge-discharge cycles, without the need for stabilizing binders or conductive additives even at moderate loadings (5mg cm-2). This desirable performance is maintained in a prototype symmetric two-electrode capacitor device, which has >99% Coloumbic efficiency and a <10 mF capacity drop over 2000 cycles. These results demonstrate that ionic PIMs function well as standalone supercapacitor electrodes and suggest ionic PIMs may perform well in other electrochemical devices such as sensors, ion-separation membranes, or displays.

Computational design of novel highly connected COFs for CH4/H2 adsorption and separation

Ten new highly connected cubic boronitrate (-B4N4O12-) base covalent organic frameworks (BN-COFs) were designed in the lta and aco topologies. These structures were optimized and characterized computationally using density functional theory (DFT) and molecular mechanics methods. The structural characterization reflects that these BN-COFs possess the appropriate structural parameters for CH4/H2 adsorption and separation, such as low density (0.52–1.28 g·cm−3), high pore porosity (22 %-72 %), appropriate pore limiting diameter (PLD, 2.45–6.71 Å) and the largest cavity diameter (LCD, 3.21–19.96 Å), large pore volume (0.15–1.37 cm3·g−1) and accessible surface area (332–3974 cm2·g−1). Grand canonical Monte Carlo (GCMC) simulations were conducted to investigated the adsorption and separation properties of CH4 and H2 in ten BN-COFs. The results indicate that the uptake capacity of methane and hydrogen in BN-COF-5, −9 and −10 has exceeded the targets set by the U.S. Department of Energy (DOE). Furthermore, the CH4/H2 selectivity of ten BN-COFs is comparable to that of typical porous materials. The outstanding CH4/H2 adsorption and separation properties of these BN-COFs can provide some references and inspirations for researchers to develop high-performance porous adsorbents in experimental studies.

Advancements in Noble Metal-Decorated Porous Carbon Nanoarchitectures: Key Catalysts for Direct Liquid Fuel Cells.

Noble-metal nanocrystals have emerged as essential electrode materials for catalytic oxidation of organic small molecule fuels in direct liquid fuel cells (DLFCs). However, for large-scale commercialization of DLFCs, adopting cost-effective techniques and optimizing their structures using advanced matrices are crucial. Notably, noble metal-decorated porous carbon nanoarchitectures exhibit exceptional electrocatalytic performances owing to their three-dimensional cross-linked porous networks, large accessible surface areas, homogeneous dispersion (of noble metals), reliable structural stability, and outstanding electrical conductivity. Consequently, they can be utilized to develop next-generation anode catalysts for DLFCs. Considering the recent expeditious advancements in this field, this comprehensive review provides an overview of the current progress in noble metal-decorated porous carbon nanoarchitectures. This paper meticulously outlines the associated synthetic strategies, precise microstructure regulation techniques, and their application in electrooxidation of small organic molecules. Furthermore, the review highlights the research challenges and future opportunities in this prospective research field, offering valuable insights for both researchers and industry experts.

A Three-Dimensional AgNPs/TiO2/Ti3C2Tx Composite for Label-Free Thrombin Aptamer Sensor

A one-step hydrothermal method was employed to synthesize a three-dimensional (3D) AgNPs/TiO2/Ti3C2Tx composite. Hydrothermal conditions were used to promote the growth of TiO2 nanorods on the Ti3C2Tx sheet, resulting in the formation of a three-dimensional composite nanomaterial. Glutamic acid served as both a reducing agent and a stabilizer to load Ag nanoparticles (AgNPs) onto the 3D composite nanomaterial. The structure of the composite material provided a large accessible surface area, facilitating the anchoring of Ag NPs. Thrombin aptamers were then linked to Ag NPs through Ag-S bonds, establishing a sensitive and label-free aptasensor for thrombin detection. The proposed aptasensor demonstrated excellent electrochemical performance, with a broad linearity range of 5.0 fM to 500 nM and a relatively low detection limit of 2.0 fM (S/N = 3). These findings indicate the potential of Ag NPs/TiO2/Ti3C2Tx in the development of promising electrochemical biosensors.

Ultrasmall Pd nanocrystals confined into Co-based metal organic framework-decorated MXene nanoarchitectures for efficient methanol electrooxidation

The natural scarcity and insufficient utilization of noble metal-based catalysts bring a heavy block in the way of the widespread applications of direct methanol fuel cells. Herein, we propose a feasible bottom-up approach to the construction of ultrasmall Pd nanocrystals confined into Co-based metal organic framework-decorated Ti3C2Tx MXene (Pd/MOF-MX) nanoarchitectures via a controllable solvothermal process. The ultrathin MXene nanolamellas and porous Co-based MOFs constitute an ideal hybrid carrier with high electron conductivity and large accessible surface areas, which not only facilitates the size restriction and uniform dispersion of Pd nanocrystals, but also ameliorates their intrinsic catalytic activity through the direct electronic interactions. By virtue of the pronounced synergistic coupling effects, the newly-developed Pd/MOF-MX nanoarchitectures exhibit markedly enhanced electrocatalytic properties towards the methanol oxidation reaction, including a large electrochemically active surface area of 116.7 m2 g−1, a high mass activity of 1700.4 mA mg−1 as well as a satisfactory long-term durability, which are superior to those of traditional Pd electrocatalysts anchored on carbon blacks, carbon nanotubes, graphene, and undecorated MXene matrixes.

Heterointerface engineering of rhombic Rh nanosheets confined on MXene for efficient methanol oxidation

Although metallic rhodium (Rh) is regarded as a promising platinum-alternative anode catalyst of direct methanol fuel cell (DMFC), the conventional “particle-to-face” contact model between Rh and matrix largely limits the overall electrocatalytic performance due to their insufficient cooperative effects. Herein, we report a controllable and robust heterointerface engineering strategy for the bottom-up fabrication of rhombic Rh nanosheets in situ confined on Ti3C2Tx MXene nanolamellas (Rh NS/MXene) via a convenient stereoassembly process. This unique design concept gives the resulting 2D/2D Rh NS/MXene heterostructure intriguing textural features, including large accessible surface areas, strong “face-to-face” interfacial interactions, homogeneous Rh nanosheet distribution, ameliorative electronic structure, and high electronic conductivity. As a consequence, the as-prepared Rh NS/MXene nanoarchitectures exhibit exceptional electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area of 126.2 m2 g−1Rh, a high mass activity of 1056.9 mA mg−1Rh, and a long service life, which significantly outperform those of conventional particle-shaped Rh catalysts supported by carbon black, carbon nanotubes, reduced graphene oxide, and MXene matrixes as well as the commercial Pt nanoparticle/carbon black and Pd nanoparticle/carbon black catalysts with the same noble metal loading amount. Density functional theory calculations further demonstrate that the direct electronic interaction at the well-contacted 2D/2D heterointerfaces effectively enhances the adsorption energy of Rh nanosheets and induces a left shift of the d-band center, thereby making the Rh NS/MXene configuration suffer less from CO poisoning. This work highlights the importance of rational heterointerface design in the construction of advanced noble metal/MXene electrocatalysts, which may provide new avenues for developing the next-generation DMFC devices.

Hierarchical porous carbon guided by constructing organic-inorganic interpenetrating polymer networks to facilitate performance of zinc hybrid supercapacitors

Customized design of well-defined cathode structures with abundant adsorption sites and rapid diffusion dynamics, holds great promise in filling capacity gap of carbonaceous cathodes towards high-performance Zn-ion hybrid supercapacitors (ZHC). Herein, we fabricate a series of dynamics-oriented hierarchical porous carbons derived from the unique organic-inorganic interpenetrating polymer networks. The interpenetrating polymer networks are obtained through physically knitting polyferric chloride (PFC) network into the highly crosslinked resorcinol-formaldehyde (RF) network. Instead of covalent bonding, physical interpenetrating force in such RF-PFC networks efficiently relieves the RF skeleton shrinkage upon pyrolysis. Meanwhile, the in-situ PFC network sacrifices as a structure-directing agent to suppress the macrophase separation, and correspondingly 3D hierarchical porous structure with plentiful ion-diffusion channels (pore volume of 1.35 cm3/g) is generated in the representative HPC4via nanospace occupation and swelling effect. Further removal of Fe fillers leaves behind a large accessible specific surface area of 1550 m2/g for enhanced Zn-ion adsorption. When used as the cathode for ZHC, HPC4 demonstrates a remarkable electrochemical performance with a specific capacity of 215.1 mAh/g at 0.5 A/g and a high Zn2+ ion diffusion coefficient of 11.1 × 10−18 cm2/s. The ZHC device yields 117.0 Wh/kg energy output at a power density of 272.1 W/kg, coupled with good cycle lifespan (100,000 cycles@10 A/g). This work inspires innovative insights to accelerate Zn diffusion dynamics by structure elaboration towards high-capacity cathode materials.

Unravelling the enhanced capacitive desalination behavior of nanoneedle-like NiFe2O4

In this work, the nanoneedle-like NiFe2O4 (NFO) has been prepared by a template method and post annealing process for capacitive deionization (CDI) with enhanced performance. Owing to the unique structure, the nanoneedle-like NFO provides large accessible surface area, which benefits to offer abundant electroactive sites for electrosorption. Meanwhile, the salty ions diffusion and electron exchange are promoted by needle-like structure. Further, it is found that the NFO annealed at 450 °C (NFO-450) demonstrate the high crystallinity, rich mesopores and exceptional electrochemical properties. As electrode for CDI, the NFO-450 has manifested the high desalting capacity of 1.62 mmol/g when the effective loading mass of both electrodes is 23.6 mg. Interestingly, the desalting capacity realizes the linear correlation with the mass of NFO electrode ranging from 23.6 to 45.8 mg. The mechanism analysis stands out that the Na+ are captured by NFO, accompanied by the reduction of Ni3+ to Ni2+ in the 1st cycle. Afterwards, the Na+ can be electrostatically removed by the NFO//AC system.

Pore engineering in robust carbon nanofibers for highly efficient capacitive deionization

Capacitive deionization (CDI) is considered as a revolutionary desalination method to alleviate the global water crisis. However, the current carbon-based CDI cells are constrained by the inferior desalination efficiency, resulting from the undesirable pore structure and sluggish electron/ion transport. Herein, a new porogen of silicalite-1 is proposed for the tailorable fabrication of flexible porous carbon nanofibers (PCNFs) by electrospinning, carbonization and alkali etching, where the surface area, total pore volume, mechanical robustness, specific capacitance, and electrosorption performance of the developed PCNFs are associated with the silicalite-1 dosage. The symmetric CDI unit assembled by the freestanding PCNF membrane electrodes shows a state-of-the-art desalination capacity (38.64 mg g−1), a remarkable salt removal rate (12.1 mg g−1 min−1), a desirable charge efficiency (82.36 %), an acceptable energy consumption (0.668 Wh g−1), and a satisfactory cyclic durability, and such excellent deionization performance can be explained by that the abundant hierarchical pores, the large accessible surface area, and the interconnected conductive carbon network effectively expedite the electron/ion transport. Additionally, the home-made CDI device has a favorable desalination capability toward the high-ion concentration seawater from the Yellow Sea (Xiaomai Island). This work not only validates the feasibility of silicalite-1 as the pore-forming agent for the targeted preparation of flexible PCNFs, but also it highlights the potential of pore engineering in freestanding PCNFs for advanced CDI.

Anchoring Ultrasmall Pt Nanocrystals onto Carbon Nanohorn-Decorated 3D Graphene Networks to Boost Methanol Oxidation Reaction

The successful commercialization of the direct methanol fuel cell (DMFC) is inseparable from the development of advanced Pt-based anode catalysts with high electrocatalytic activity and acceptable manufacturing cost. Here, we present a robust bottom-up strategy to anchor ultrasmall Pt nanocrystals with an average diameter of only 2.3 nm onto carbon nanohorn-decorated three-dimensional (3D) graphene networks (Pt/CNH-G) through a controllable self-assembly process. The as-derived 3D Pt/CNH-G catalysts manifest a series of distinctive architectural advantages, such as interconnected porous frameworks, large accessible surface areas, plentiful active cones, highly dispersed Pt nanoparticles, and good electron conductivity. Consequently, the optimized Pt/CNH-G catalyst is endowed with exceptional methanol oxidation properties with a large electrochemical active surface area of 128.6 m2 g-1, a high mass activity of 1626.0 mA mg-1, and excellent long-term stability, which are significantly superior to those of conventional Pt catalysts supported by carbon black, carbon nanotube, carbon nanohorn, and graphene matrices.

Facile wet mechanochemistry coupled K2FeO4 activation to prepare functional coal-derived hierarchical porous carbon for supercapacitors

The high power characteristics of supercapacitors (SC) are attractive for grid scale energy storage. The core to achieve the large scale application of SC lies in the preparation of high performance electrode materials. Herein, a facile wet mechanochemistry (WMC) coupled K2FeO4 activation is used to fabricate O/N/S doped coal-derived hierarchical porous carbon (CHPC). K2FeO4 generates high-energy sputtering O2 under mechanical force to impact precursor, leading to an increase in lattice defects, and full exposure of active sites, which facilitates activation of precursor and coupling of heteroatoms. Furthermore, K2FeO4 has the pore forming ability of K-based component and the catalytic graphitization effect of Fe-based component, which could synergistically regulate pore structure and graphitization of CHPC. Experimental exploration combined with density functional theory calculation showed that the unique micro-mesopores structure of CHPC provides a fast ion transport channel and a large ion accessible specific surface area (SSSA). Meanwhile, the high heteroatom doping and graphitization synergistic promote ion storage (high adsorption energy, Eads) and electron transport. The specific capacitance (C) of optimized CHPC900 can obtain 335 F g−1 under 0.5 A g−1. The C retention is 96.2% after 10,000 cycles at 1 A g−1. CHPC900//CHPC900 delivers remarkable energy/power characteristics (9.9 Wh kg−1 of 125 W kg−1).

Ferric ion-assisted assembly of MXene/TiO2-graphene aerogel for ionic liquid-based supercapacitors

To achieve pseudocapacitance by driving reversible redox reactions is scientifically appealing to realize high energy density of supercapacitors (SCs). In this work, a unique ferric ions-assisted self-assembly MXene/TiO2-graphene aerogel composite (MXene/TiO2-Fe-G) is developed. The MXene/TiO2-Fe-G composite has a 3D hierarchical porous framework, large accessible specific surface area, and amorphous TiO2 modified on the surface of MXene nanosheets. Importantly, amorphous TiO2, generated from the partial oxidation of MXene, can contribute enormous pseudocapacitance via the reversible redox reaction with Lithium ions. In addition, ferric cations with variable valence states can also provide pseudocapacitance. A trinary ionic liquid-based electrolyte (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide-acetonitrile-lithium bis(trifluoromethanesulfonyl)imide, EmimTFSI-ACN-LiTFSI) with a wide electrochemical stability potential window is also formulated to match the new material. Consequently, the MXene/TiO2-Fe-G composite as the negative electrode shows a superb specific capacitance of 196.4 F g−1 at 1 A g−1. An asymmetric supercapacitor assembled with the MXene/TiO2-Fe-G anode and self-synthesized nitrogen-doped reduced graphene oxide aerogel (N-RGA) cathode can deliver a high energy density of 54 Wh kg−1 at a high-power density of 1737 W kg−1. This work provides a possibility of implementing pseudocapacitance by changing the morphology and structure of MXene composites to match the ionic liquid-based electrolyte, which can considerably enhance the performance of MXene-based SCs.

Production of high-carbon-number bio-aviation fuels from furans using sulfated zirconia and silica-alumina aerogel catalysts

Lignocellulose can help produce fuels in biorefineries through its fractionated components such as cellulose, hemicelluloses, and lignin. For instance, hemicellulose-derived xylose has been studied for obtaining petroleum-substituting fuels. Therefore, in this study, catalytic hydroalkylation/alkylation (HAA) of xylose-derived 2-methylfuran (2-MF) with butanal was targeted to selectively produce high-carbon-number diesel fuels. To that end, silica–alumina (SiAl) aerogels with different Si/Al ratios and a series of sulfated zirconia (SZ) compounds calcined at various temperatures were prepared as catalysts to overcome the limitations of conventional hazardous homogeneous acid catalysts. The activity of the SiAl catalysts in forming the desired HAA product, 5,5-bissylvylbutane (denoted as BB), was found to be directly related to the number of acid sites and acid density. Moreover, increasing the Si/Al molar ratio, which reduced the acid density and number of acid sites, led to lower 2-MF conversions and BB yields. The optimal 2-MF conversion and BB yield with the SiAl catalysts (67 % and 45 %, respectively) were achieved using a Si/Al ratio of 8:2 mol/mol. Furthermore, SZ calcined at 700 °C (denoted as SZ-700) exhibited the highest activity among the SZ catalysts (72 % 2-MF conversion, 63 % BB yield), despite having the fewest acid sites and lowest acid density. This was presumably because of the physical structure of SZ-700, which featured mixed monoclinic and tetragonal phases, many oxygen vacancies, and a large accessible external surface area, which facilitated the HAA reactions. Hydrogenation and hydrodeoxygenation (HDO) of BB were performed thereafter using Pd/C and Ru/SiO2–Al2O3 catalysts, respectively. The resulting deoxygenated hydrocarbons comprised 15.1 % light hydrocarbons (C4–C8) and 83.1 % heavier hydrocarbons (C9–C20). Simulated distillation analysis of the post-HDO product distribution indicated that the liquid-phase product contained 70 % high-carbon-number bio-aviation fuels.

Microfluidic-Assembled Covalent Organic Frameworks@Ti3 C2 Tx MXene Vertical Fibers for High-Performance Electrochemical Supercapacitors.

The delicate design of innovative and sophisticated fibers with vertical porous skeleton and eminent electrochemical activity to generate directional ionic pathways and good faradic charge accessibility is pivotal but challenging for realizing high-performance fiber-shaped supercapacitors (FSCs). Here, we develop hierarchically ordered hybrid fiber combined vertical-aligned and conductive Ti3 C2 Tx MXene (VA-Ti3 C2 Tx ) with interstratified electroactive covalent organic frameworks LZU1 (COF-LZU1) by one-step microfluidic synthesis. Due to the incorporation of vertical channels, abundant redox active sites and large accessible surface area throughout the electrode, the VA-Ti3 C2 Tx @COF-LZU1 fibers express exceptional gravimetric capacitance of 787 F g-1 in three-electrode system. Additionally, the solid-state asymmetric FSCs deliver prominent energy density of 27Wh kg-1 , capacitance of 398 F g-1 and cycling life of 20000 cycles. The key to high energy storage ability originates from the decreased ions adsorption energy and ameliorative charge density distribution in vertically aligned and active hybrid fiber, accelerating ions transportation/accommodation and interfacial electrons transfer. Benefiting from excellent electrochemical performance, the FSCs offer sufficient energy supply to power watch, flag and digital display tube as well as be integrated with sensor to detect pulse signals, which opens a promising route for architecting advanced fiber towards carbon neutrality market beyond energy-storage technology. This article is protected by copyright. All rights reserved.

Dynamic in situ growth of bonded-phase silica nanospheres on silica capillary inner walls for open-tubular liquid chromatography

Silica nanospheres (SNS) were grown on the inner walls of silica capillaries through a dynamic in situ nucleation process to prepare a highly porous and large accessible surface area substrate. The SNS were then functionalized with octadecyl (C18), 3-aminopropyltriethoxysilane (APTES), beta-cyclodextrin (β-CD), and amino groups to develop robust and efficient chromatographic stationary phases. The modified silica capillaries were exploited for open-tubular liquid chromatography (OT-LC) and open-tubular capillary electrochromatography (OT-CEC) applications. The prepared stationary phases were compared to conventional capillaries in terms of separation performance. The synthesis process was optimized, and the bonded-phase stationary phases were characterized by the electron microscopy technique. The effects of different solvents, additives, and functional groups on the geometry and chromatographic resolving power of the SNS were envisaged. The capillaries modified with octadecyl groups were evaluated for the separation of non-steroidal anti-inflammatory drugs, phenones, alkenylbenzenes, and enantiomers of chlorophenoxy herbicides. As an application instance, an SNS-C18-coated capillary was utilized for the separation of alkenylbenzenes from clove extract and protein digest medium, through OT-LC and OT-CEC techniques, respectively. The β-CD functionalized capillary was applied for the OT-CEC separation of a dichlorprop racemic mixture.Graphical abstract

Ni–Fe layered double hydroxide nanosheets immobilized on three-dimensional crosslinked MoS2-graphene architectures for efficient electrocatalytic hydrogen evolution

Two-dimensional layered double hydroxide (LDH) nanosheets are regarded as promising cathode catalysts toward the hydrogen evolution reaction (HER), while their overall electrocatalytic capability remains to be optimized before practical application. Herein, we demonstrate a robust bottom-up approach to fabricate ultrathin Ni–Fe LDHs immobilized on three-dimensional crosslinked architectures built from MoS2 nanosheets and graphene (LDH/MoS2-G) through a convenient and cost-effective co-assembly process. This unique structural design is able to acquire a series of textural merits, such as three-dimensional interconnected frameworks with ultrathin walls, abundant porous channels, large accessible surface areas, optimized electronic structures, and high electric conductivity, which can effectively accelerate the electrochemical kinetics during the HER process. Consequently, the resulting LDH/MoS2-G architectures exhibit an exceptional HER performance with a low onset potential, a small Tafel slope, and a long lifespan in the alkaline medium, more competitive than that of bare LDH, MoS2, graphene as well as binary LDH/graphene and MoS2/graphene electrocatalysts.

Application of Inorganic Quantum Dots in Advanced Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have emerged as one of the most attractive alternatives for post-lithium-ion battery energy storage systems, owing to their ultrahigh theoretical energy density. However, the large-scale application of Li-S batteries remains enormously problematic because of the poor cycling life and safety problems, induced by the low conductivity , severe shuttling effect, poor reaction kinetics, and lithium dendrite formation. In recent studies, catalytic techniques are reported to promote the commercial application of Li-S batteries. Compared with the conventional catalytic sites on host materials, quantum dots (QDs) with ultrafine particle size (<10nm) can provide large accessible surface area and strong polarity to restrict the shuttling effect, excellent catalytic effect to enhance the kinetics of redox reactions, as well as abundant lithiophilic nucleation sites to regulate Li deposition. In this review, the intrinsic hurdles of S conversion and Li stripping/plating reactions are first summarized. More importantly, a comprehensive overview is provided of inorganic QDs, in improving the efficiency and stability of Li-S batteries, with the strategies including composition optimization, defect and morphological engineering, design of heterostructures, and so forth. Finally, the prospects and challenges of QDs in Li-S batteries are discussed.

Directly Grow Ultrasmall Co2P QDs on MoS2 Nanosheets to Form Heterojunctions Greatly Boosting Electron Transfer toward Hydrogen Evolution

A green process to produce an efficient and inexpensive electrocatalyst toward hydrogen evolution reaction (HER) is of importance for hydrogen energy. Here, an efficient HER electrocatalyst is made by electrochemically depositing Co2P quantum dots (QDs) on MoS2-carbon cloth (Co2P QDs/MoS2-CC). Due to the MoS2 porous structure, ∼3 nm Co2P QDs uniformly deposit on MoS2. The produced unique 3D-structured Co2P QDs/MoS2-CC not only prevents an agglomeration of the active material and improves the diffusion rate of H2 but also renders large accessible surface area and hierarchical pores for high-density reaction sites and enhanced mass transport rate. Experimental results and theoretical analysis of this unique heterostructure indicate that the evolution process of hydrogen is dominated by proton adsorption, and the introduction of sufficient edge active sites can significantly promote the HER. As a consequence, the hierarchical Co2P QDs/MoS2-CC electrocatalyst affords an ultra-low overpotential (41 mV at a current density of 10 mA cm–2) that ranks the best among all reported MoS2 HER catalysts and exhibits excellent durability in 1 M KOH solutions, thus holding great promise for the practical application while shedding on fundamentals to nanoengineering an efficient electrocatalyst.