Synthesizing Pd-based high entropy alloy nanoclusters for enhanced oxygen reduction.

We report the synthesis of uniform Pd-based high-entropy alloy clusters via rapid Joule heating. The quinary PdMnFeCuNi clusters exhibit 4.95 times higher mass activity than the Commercial Pt/C for the oxygen reduction reaction, and outstanding stability with only 2 mV decay in the half-wave potential after 20 000 cycles of testing.

Selective edge etching of Pd metallene for enhanced formic acid electrooxidation.

We develop a facile, selective edge etching strategy to create edge sites in Pd metallene using acetic acid. The created edge sites remarkably increase the electrochemically active surface area but reduce the charge transfer resistance, resulting in significant enhancement of catalytic activity and stability toward formic acid oxidation.

Three-dimensional Ni foam supported NiCoO2@Co3O4 nanowire-on-nanosheet arrays with rich oxygen vacancies as superior bifunctional catalytic electrodes for overall water splitting.

Earth abundant transition metal oxide (EATMO)-based bifunctional catalysts for overall water splitting are highly desirable, but their performance is far from satisfactory due to low intrinsic activities of EATMOs toward electrocatalysis of both oxygen and hydrogen evolution reactions and poor electron transfer and transport capabilities. A three-dimensional (3-D) Ni-foam-supported NiCoO2@Co3O4 nanowire-on-nanosheet heterostructured array with rich oxygen vacancies has been synthesized, showing OER activity superior to most reported catalysts and even much higher than Ru and Ir-based ones and HER activity among the highest reported for non-noble-metal-based catalysts. The excellent activities are ascribed to the highly dense, ultrathin nanowire arrays epitaxially grown on an interconnected layered nanosheet array greatly facilitating electron transfer and providing numerous electrochemically accessible active sites and the high content of oxygen vacancies on nanowires greatly promoting OER and HER. When adopted as bifunctional electrodes for overall water splitting, this heterostructure shows an overvoltage (at 10 mA cm-2) lower than most reported electrolyzers and high stability. This work not only creates a 3-D EATMO-based integrated heterostructure as a low-cost, highly efficient bifunctional catalytic electrode for water splitting, but also provides a novel strategy to use unique heteronanostructures with rich surface defects for synergistically enhancing electrocatalytic activities.

Tensile-Strained Holey Pd Metallene toward Efficient and Stable Electrocatalysis.

Noble metal-based metallenes are attracting intensive attention in energy catalysis, but it is still very challenging to precisely control the surface structures of metallenes for higher catalytic properties on account of their intrinsic thermodynamic instability. Herein, the synthesis of tensile-strained holey Pd metallene by oxidative etching is reported using hydrogen peroxide, which exhibits highly enhanced catalytic activity and stability in comparison with normal Pd metallene toward both oxygen reduction reaction and formic acid oxidation. The pre-prepared Pd metallene functions as a catalyst to decompose hydrogen peroxide, and the Pd atoms in amorphous regions of Pd metallene are preferentially removed by the introduced hydrogen peroxide during the etching process. The greatly enhanced ORR activity is mainly determined by the strong electrostatic repulsion between intermediate O* and the dopant O, which balances the adsorption strength of O* on Pd sites, ultimately endowing a weakened adsorption energy of O* on TH-Pd metallene. This work creates a facile and economical strategy to precisely shape metallene-based nanoarchitectures with broad applications for energy systems and sensing devices.

In situ self-assembled macroporous interconnected nanosheet arrays of Ni-1,3,5-benzenetricarboxylate metal - organic framework on Ti mesh as high-performance oxygen evolution electrodes.

Highly efficient metal-organic framework (MOF)-based oxygen evolution reaction (OER) catalysts are desirable for water splitting, but their development remains challenging due to poor accessibility of coordinatively unsaturated metal (cum) sites and low intrinsic activity. A large-area three-dimensional (3-D) macroporous interconnected nanosheet array of Ni-1,3,5-benzenetricarboxylate has been in situ self-assembled on Ti mesh (TM) by using ethanol as the solvent and high-affinity oxide layer on TM to promote in situ nucleation. The obtained nanoarchitecture exhibits much superior catalytic activity compared to most reported catalysts including MOF-based catalysts, other precious-metal-free ones, and Ir/Ru-based ones. Additionally, this electrode undergoes no current decay after 300 cyclic voltammetry (CV) cycles and can maintain at 250 mA cm-2 for over 266 h. The excellent catalytic performance is mainly due to the 3-D macroporous and interconnected nanosheet array structure improving cum site exposure and charge transport and in situ activated cum cations enhancing OH- adsorption. This work not only develops a facile and economical approach to synthesize 3-D macroporous interconnected MOF nanosheet arrays to simultaneously increase the number, exposure, and intrinsic activity of active sites and facilitate charge transport for high-performance eletrocatalysis, but provides scientific insights into the mechanisms for self-assembly of this unique nanoarchitecture and for the high OER performance.

Current commercial dPCR platforms: technology and market review.

Digital polymerase chain reaction (dPCR) technology has provided a new technique for molecular diagnostics, with superior advantages, such as higher sensitivity, precision, and specificity over quantitative real-time PCRs (qPCR). Eight companies have offered commercial dPCR instruments: Fluidigm Corporation, Bio-Rad, RainDance Technologies, Life Technologies, Qiagen, JN MedSys Clarity, Optolane, and Stilla Technologies Naica. This paper discusses the working principle of each offered dPCR device and compares the associated: technical aspects, usability, costs, and current applications of each dPCR device. Lastly, up-and-coming dPCR technologies are also presented, as anticipation of how the dPCR device landscape may likely morph in the next few years.

Converting inert AlOOH into efficient electrocatalyst for oxygen evolution reaction via structural/electronic modulation.

Efficient and stable water-splitting electrocatalysts play a key role to obtain green and clean hydrogen energy. However, only a few kinds of materials display an intrinsically good performance towards water splitting. It is significant but challengeable to effectively improve the catalytic activity of inert or less active catalysts for water splitting. Herein, we present a structural/electronic modulation strategy to convert inert AlOOH nanorods into catalytic nanosheets for oxygen evolution reaction (OER) via ball milling, plasma etching and Co doping. Compared to inert AlOOH, the modulated AlOOH delivers much better OER performance with a low overpotential of 400 mV at 10 mA cm-2 and a very low Tafel slope of 52 mV dec-1, even lower than commercial OER catalyst RuO2. Significant performance enhancement is attributed to the electronic and structural modulation. The electronic structure is effectively improved by Co doping, ball milling-induced shear strain, plasma etching-caused rich vacancies; abrupt morphology/microstructure change from nanorod to nanoparticle to nanosheet, as well as rich defects caused by ball milling and plasma etching, can significantly increase active sites; the free energy change of the potential determining step of modulated AlOOH decreases from 2.93 eV to 1.70 eV, suggesting a smaller overpotential is needed to drive the OER processes. This strategy can be extended to improve the electrocatalytic performance for other materials with inert or less catalytic activity.

Integrating high ionic conductive PDOL solid/gel composite electrolyte for enhancement of interface combination and lithium dentrite inhibition of solid-state lithium battery.

High interface impedance, slow ion transmission, and easy growth of lithium dendrites in solid-state lithium battery are main obstacles to its development and application. Good interface combination and compatibility between electrolyte and electrodes is an important way to solve these problems. In this work, we successfully combined a high ionic conductive polymerized 1,3-dioxolane (PDOL) solid-state electrolyte and a PDOL gel-state electrolyte to form a rigid-flexible composite structural electrolyte and realized the gelation modification of solid electrolyte/electrode interface. This "PDOL SE + PDOL Gel" composite structure not only improves the electrode/electrolyte interfacial contact, reduces the interfacial impedance, but also inhibits the growth of lithium dendrites in the interface between lithium anode and electrolyte by forming an uniform Li-Zr-O and LiF composite protection layer. This composite electrolyte has high ionic conductivity of 5.96 × 10-4 S/cm and wide electrochemical stability window of 5.0 V. The Li/PDOL SE + PDOL Gel/Li cells can be cycled stably for nearly 400 h at a current density of 1.0 mA/cm2. The assembled LiCoO2/PDOL SE + PDOL Gel/Li cells can be cycled for 250 cycles at 0.5 C with a capacity retention of 80%. This PDOL solid/gel composite electrolyte shows high promising commercial application prospect due to its high security performance, excellent interfacial properties and dendrite inhibition ability.

Controllable Synthesis of Web-Footed PdCu Nanosheets and Their Electrocatalytic Applications.

Morphological control of noble-metal-based nanocrystals has attracted enormous attention because their catalytic behaviors can be optimized well by adjusting the size and shape. Herein, the controllable synthesis of web-footed PdCu nanosheets via a facile surfactant-free method is reported. It is discovered that the Cu(II) precursor in this synthetic system displays a critical role in growing branches along the lateral of nanosheets. This work demonstrates a Pd-based alloy nanoarchitecture for efficient and stable electrocatalysis of both ethanal and formic acid oxidation reactions.

Dynamically self-assembled adenine-mediated synthesis of pristine graphene-supported clean Pd nanoparticles with superior electrocatalytic performance toward formic acid oxidation.

Pd-based catalysts with maximized exposure of active sites, ultrafast electron transport, and cocatalyst-promoted intrinsic activity are highly desirable for the formic acid oxidation reaction (FAOR), but their fabrication presents a formidable challenge. For the first time, dynamic self-assembly of adenine has been utilized for growth of ultrasmall, highly dispersed, and clean Pd NPs on pristine graphene. The obtained nanohybrid shows remarkably enhanced FAOR catalytic activity and durability compared to Pd NPs directly grown on pristine graphene and commercial Pd/C. The activity is also among the highest for Pd-based catalysts. The excellent catalytic performance is due to well-dispersed, ultrasmall, and clean Pd NPs intimately grown on pristine graphene offering numerous electrochemically accessible active sites and preserving high intrinsic catalytic activity of Pd, great cocatalytic effect of pristine graphene enhancing CO tolerance and intrinsic activity of Pd, and robust attachment of Pd with high CO tolerance on graphene providing high durability. This study develops a facile, mild, and economical strategy to create pristine graphene supported clean Pd NPs with outstanding FAOR catalytic performance, and also sheds light on the mechanism of dynamically self-assembled adenine-mediated synthesis, which is extendable to fabricate other nanohybrids.

Directionally In Situ Self-Assembled, High-Density, Macropore-Oriented, CoP-Impregnated, 3D Hierarchical Porous Carbon Sheet Nanostructure for Superior Electrocatalysis in the Hydrogen Evolution Reaction.

3D ZIF-67-particles-impregnated cellulose-nanofiber nanosheets with oriented macropores are synthesized via directional-freezing-assisted in situ self-assembly, and converted to 3D CoP-nanoparticle (NP)-embedded hierarchical, but macropores-oriented, N-doped carbon nanosheets via calcination and phosphidation. The obtained nanoarchitecture delivers overpotentials at 10 and 50 mA cm-2 and Tafel slope of 82.1 and 113.4 mV and 40.8 mV dec-1 in 0.5 M H2 SO4 , and of 97.1 and 136.6 mV and 51.2 mV dec-1 in 1 M KOH, all of which are superior to those of the most reported non-noble-metal-based hydrogen evolution reaction (HER) catalysts. This catalyst even surpasses commercial Pt/C for a much lower overpotential at high current densities, which is essential for large-scale hydrogen production. Its catalytic activity can be further optimized to become one of the best in both 0.5 M H2 SO4 and 1 M KOH. The outstanding catalytic activity is ascribed to the uniformly-dispersed small CoP NPs in the 3D carbon sheets and the hierarchical nanostructure with rich oriented pores. This work develops a facile, economical, and universal self-assembly strategy to fabricate uniquely nanostructured hybrids to simultaneously promote charge transfer and mass transport, and also offers an inexpensive and high-performance HER catalyst toward industry-scale water splitting.

In situ self-assembled N-rich carbon on pristine graphene as a highly effective support and cocatalyst of short Pt nanoparticle chains for superior electrocatalytic activity toward methanol oxidation.

Highly conductive cocatalysts with great promotion effects are critical for the development of pristine graphene supported Pt-based catalysts for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). However, identification of these cocatalysts and controlled fabrication of Pt/cocatalyst/graphene hybrids with superior catalytic performance present great challenges. For the first time, pristine graphene supported N-rich carbon (NC) has been controllably fabricated via ionic-liquid-based in situ self-assembly for in situ growth of small and uniformly dispersed Pt NP chains to improve the MOR catalytic activity. It is discovered that the NC serves simultaneously as a linker to facilitate in situ nucleation of Pt, a stabilizer to restrict its growth and aggregation, and a structure-directing agent to induce the formation of Pt NP chains. The obtained nanohybrid shows a much higher forward peak current density than commercial Pt/C and most reported noncovalently functionalized carbon (NFC) supported Pt catalysts, a lower onset potential than almost all commercial Pt/C and NFC supported Pt, and greatly enhanced durability compared to graphene supported Pt NPs and commercial Pt/C. The superior catalytic performance is ascribed to the uniformly dispersed, small-diameter, and short Pt NP chains supported on highly conductive G@NC providing high ECSA and improved CO tolerance and the NC with high content of graphitic N greatly enhancing the intrinsic activity and CO tolerance of Pt and offering numerous binding sites for robustly attaching Pt. This work not only identifies and controllably fabricates a novel cocatalyst to significantly promote the catalytic activity of pristine graphene supported Pt but provides a facile and economical strategy for the controlled synthesis of high-performance integrated catalysts for the MOR in DMFCs.

Ionic liquid in situ functionalized carbon nanotubes as metal-free catalyst for efficient electrocatalytic hydrogen evolution reaction.

The development of cost-effective and high-performance catalysts for the production of hydrogen via electrocatalytic water splitting is crucial for meeting the increasing energy demand and expanding the hydrogen economy. In this study, a series of metal-free carbon nanotube (CNT) catalysts were designed and in situ functionalized by imidazolium ionic liquids (ILs) for enhanced electrocatalytic hydrogen evolution reaction (HER). The theoretical calculations and experimental results reveal that the functionalization of CNTs with imidazolium ILs facilitated the electron transfer process and exhibited superior hydrogen adsorption, thereby enhancing the performance of the HER. In particular, CNT-IM-Cl displays excellent electrocatalytic activity and shows a low onset overpotential and Tafel slope of 80 mV and 38 mV dec-1, respectively. This study highlights the significant potential of IL in situ functionalized metal-free CNTs for the electrocatalytic HER and provides insight into the structure design of highly efficient electrocatalysts.

Enhanced ionic conductivity and lithium dendrite suppression of polymer solid electrolytes by alumina nanorods and interfacial graphite modification.

Poor room-temperature ionic conductivity and lithium dendrite formation are the main issues of solid electrolytes. In this work, rod-shaped alumina incorporation and graphite coating were simultaneously applied to poly (propylene carbonate) (PPC)-based polymer solid electrolytes (Wang et al., 2018). The obtained alumina modified solid electrolyte membrane (Al-SE) achieves a high ionic conductivity of 3.48 × 10-4 S/cm at room temperature with a wide electrochemical window of 4.6 V. The assembled NCM622/Al-SE/Li solid-state battery exhibits initial discharge capacities of 198.2 mAh/g and 177.5 mAh/g at the current density of 0.1 C and 0.5 C, with the remaining capacities of 165.8 mAh/g and 161.3 mAh/g after 100 cycles respectively. The rod-shaped structure of Al2O3 provides fast transport channels for lithium ions and its Lewis acidity promotes the dissociation of lithium salts and release of free lithium ions. The lithiophilic Al2O3 and Graphite form intimate contact with metallic Li and create fast Li+ conductive layers of Li-Al-O layer and LiC6 layer, thus facilitating the uniform deposition of Li and inhibiting Li dendrite formation during long-term cycling. This kind of composite Al-SE is expected to provide a promising alternative for practical application in solid electrolytes.

Weak polyelectrolyte-based multilayers via layer-by-layer assembly: Approaches, properties, and applications.

Layer-by-layer (LbL) assembly is a nanoscale technique with great versatility, simplicity and molecular-level processing of various nanoscopic materials. Weak polyelectrolytes have been used as major building blocks for LbL assembly providing a fundamental and versatile tool to study the underlying mechanisms and practical applications of LbL assembly due to its pH-responsive charge density and molecular conformation. Because of high-density uncompensated charges and high-chain mobility, weak polyelectrolyte exponential multilayer growth is considered one of the fastest developing areas for organized molecular films. In this article, we systematically review the current status and developments of weak polyelectrolyte-based multilayers including all-weak-polyelectrolyte multilayers, weak polyelectrolytes/other components (e.g. strong polyelectrolytes, neutral polymers, and nanoparticles) multilayers, and exponentially grown weak polyelectrolyte multilayers. Several key aspects of weak polyelectrolytes are highlighted including the pH-controllable properties, the responsiveness to environmental pH, and synergetic functions obtained from weak polyelectrolyte/other component multilayers. Throughout this review, useful applications of weak polyelectrolyte-based multilayers in drug delivery, tunable biointerfaces, nanoreactors for synthesis of nanostructures, solid state electrolytes, membrane separation, and sensors are highlighted, and promising future directions in the area of weak polyelectrolyte-based multilayer assembly such as fabrication of multi-responsive materials, adoption of unique building blocks, investigation of internal molecular-level structure and mechanism of exponentially grown multilayers, and exploration of novel biomedical and energy applications are proposed.

Improved Interface Stability and Room-Temperature Performance of Solid-State Lithium Batteries by Integrating Cathode/Electrolyte and Graphite Coating.

Poor interface stability is a crucial problem hindering the electrochemical performance of solid-state lithium batteries. In this work, a novel approach for interface stability was proposed to integrate the cathode/solid electrolyte by forming an electrolyte buffer layer on the rough surface of the cathode and coating a layer of graphite on the side of the electrolyte facing the lithium anode. This hybrid structure significantly improves the integration and the interface stability of the electrode/electrolyte. The interfacial resistance was dramatically reduced, the stability of the plating/stripping of Li metal was enhanced, and the growth of lithium dendrites was also inhibited due to the formation of the LiC6 transition layer. The obtained solid-state lithium battery shows enhanced rate performance at room temperature from 0.5 to 4 C and stable cycling performance at 1 C with a retention capacity of 100 mAh g-1 after 200 cycles. This integrated electrode/electrolyte design approach is expected to be widely used to improve interfacial stability and room-temperature electrochemical performance of solid-state batteries.

Non-zero-crossing current-voltage hysteresis behavior induced by capacitive effects in bio-memristor.

Capacitive devices have drawn a beautiful application scene in electronic device systems ranging from touch sensors, energy storages and multifunction transistors, but serving as memristive term is still blank. Sweet potato peel (SPP) as function layer was employed to develop the memristive device with Ag/SPP/F-doped SnO2 (FTO) structure. A current-voltage (I-V) hysteresis, which is characterized by a typical capacitive behavior, is impressively observed in the developed device. Nonvolatile data storage is feasible using the non-zero-crossing I-V hysteresis because the resistance states can be well maintained. Charge transfer at the Ag/SPP and SPP/FTO interfaces, and the interplay between Ag+ ions and charges are responsible for this non-zero-crossing I-V hysteresis behaviors. This work possibly gives an insight into the data storage in terms of a new conception electronic device based on environment-friendly material.

A novel all-fiber-based LiFePO4/Li4Ti5O12 battery with self-standing nanofiber membrane electrodes.

Electrodes with high conductivity and flexibility are crucial to the development of flexible lithium-ion batteries. In this study, three-dimensional (3D) LiFePO4 and Li4Ti5O12 fiber membrane materials were prepared through electrospinning and directly used as self-standing electrodes for lithium-ion batteries. The structure and morphology of the fibers, and the electrochemical performance of the electrodes and the full battery were characterized. The results show that the LiFePO4 and Li4Ti5O12 fiber membrane electrodes exhibit good rate and cycle performance. In particular, the all-fiber-based gel-state battery composed of LiFePO4 and Li4Ti5O12 fiber membrane electrodes can be charged/discharged for 800 cycles at 1C with a retention capacity of more than 100 mAh·g-1 and a coulombic efficiency close to 100%. The good electrochemical performance is attributed to the high electronic and ionic conductivity provided by the 3D network structure of the self-standing electrodes. This design and preparation method for all-fiber-based lithium-ion batteries provides a novel strategy for the development of high-performance flexible batteries.

Perforated Pd Nanosheets with Crystalline/Amorphous Heterostructures as a Highly Active Robust Catalyst toward Formic Acid Oxidation.

Perforated ultrathin Pd nanosheets with crystalline/amorphous heterostructures are rationally synthesized to offer a large electrochemically active surface area of 172.6 m2 g-1 and deliver a 5.6 times higher apparent reaction rate in comparison to commercial Pd/C, thus offering a facile confined growth method to generate superior catalysts.

Pristine-Graphene-Supported Nitrogen-Doped Carbon Self-Assembled from Glucaminium-Based Ionic Liquids as Metal-Free Catalyst for Oxygen Evolution.

For the first time, graphene-supported N-doped carbon (G@NC) with a high degree of N doping was synthesized by in situ self-assembly of a glucaminium-based ionic liquid on pristine graphene under hydrothermal conditions. This 2D, metal-free nanohybrid exhibited much higher catalytic activity than most reported metal-free catalysts for the oxygen evolution reaction (OER) and even state-of-the-art Ir- and Ru-based catalysts because the high content of graphitic N greatly increased the number of OER-active sites, the pristine graphene significantly promoted the OER activity of the C sites adjacent to the graphitic N atoms, and N-doped graphitic carbon remarkably enhanced the charge-transfer rate. This work not only creates a facile and economical approach to controllably fabricate pristine-graphene-supported carbon with a high N-doping level for the development of highly efficient metal-free OER catalysts but also provides insight into the mechanisms for both the in situ self-assembly and the high OER catalytic activity of G@NC.