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The development of inexpensive and efficient Pt-free electrocatalysts for the hydrogen evolution reaction (HER) is greatly crucial for water electrolysis. Tungsten carbide (WC) exhibiting a Pt-like electronic structure represents an attractive alternative, although its overall performance is limited by the strong W-H bond that impedes hydrogen desorption. Here, we employed an in-situ interface engineering strategy to construct high-performance and cost effective electrocatalysts comprising WC/tungsten phosphide (WP) heterostructures that were anchored on N,P-codoped carbon (WC/WP@NPC) via a one-step pyrolysis of a melamine polyphosphate/WO3 hybrid in an inert atmosphere. Owing to the crystal structure compatibility and electron-rich property of WP, it optimizes the electronic structure and hydrogen adsorption configuration of WC, thus significantly weakening the W-H bond with a thermoneutral Gibbs free energy of hydrogen adsorption (ΔGH*) of −0.05 eV. Additionally, NPC ensures fast electron transport and structural stability of the WC/WP@NPC ternary architecture. These synergistically lead to outstanding HER performances of the catalyst in acidic and alkaline media. Our finding offers a new strategy for designing Pt-alternative electrocatalysts with outstanding electrochemical performances for high-efficiency water splitting and other applications.

Developing bifunctional nanoplatforms integrating advanced biological imaging with high-performance therapeutic functions is interesting for nanoscience and biomedicine. Herein, thin-layered FePS3 nanosheets modified with amine polyethylene glycol (FePS3-PEG) are synthesized by ultrasonicated exfoliation of bulk FePS3 single crystals under Ar atmosphere and in situ chemical functionalization with amine PEG. The prepared FePS3-PEG nanosheets give a photothermal conversion efficiency of 22.1% under 808-nm laser and evident T1 relaxation (r1 = 2.69 (mmol L−1)−1 S−1) in external magnetic fields. Biologically experimental results in vitro and in vivo demonstrate that FePS3-PEG nanosheets have good biocompatibility and exhibit excellent photothermal therapy (PTT) effect under clear T1 weighted magnetic resonance imaging (MRI). The characteristics of FePS3-PEG nanosheets enable them to be a promising nanomedicine for T1-weighted MRI-guided near-infrared PTT of cancers.

Potassium-ion batteries (PIBs) are attracting increasing attention due to the abundance of K resources, but the sluggish kinetics and inferior cycling stability of anodes still hinder their application. Herein, we present a hybrid 1T/2H phase MoSe2 anode, which shows noticeable pseudocapacitive response and fast kinetics for K storage. Correspondingly, superior electrochemical performances including a high reversible capacity of 440 mA h g-1 after 100 cycles at 0.1 A g-1 and superb rate capacity of 211 mA h g-1 at 20.0 A g-1 are achieved. We believe this work may shed light on the phase engineering of transition metal compounds for rapid charging PIBs.

Electrocatalysts are considered the most promising candidates in ameliorating the slow kinetics of Li-S batteries (LSBs), however, the issue of insufficient catalytic capability remains to be addressed. Herein, we report an integrated catalytic network comprising graphitic carbon-encapsulated/bridged ultrafine NiCoP embedded in N, P-codoped carbon (GC-uNiCoP@NPC) as a highly competent catalyst for sulfur-based species conversions. By profiling the evolution map of Li-S chemistry via operando kinetic analyses, GC-uNiCoP@NPC is demonstrated to possess versatile yet efficient catalytic activity for sulfur reduction/evolution reactions, especially the rate-determining heterogeneous phase transitions. As a result, GC-uNiCoP@NPC enables high capacity and stable cycling of sulfur cathode under high areal loading and lean electrolyte. Moreover, pouch cells assembled under practical conditions present promising performance with a specific energy of 302 Wh kg

Since H5N1 virus is a highly infectious pathogen that causes outbreaks of avian influenza, developing a sensitive and rapid diagnostic platform to sense it becomes significant. Here, a novel label-free fluorescence sensing platform based on DNA-templated silver nanoclusters (DNA-Ag NCs) is developed to detect the H5N1 gene sequence representing H5N1 virus. The three-segment-branched DNA structure with closed cytosine-rich loop is designed as an effective template to produce fluorescent Ag NCs, which is different with the previous design of cytosine-rich loop formed by hairpin-like single-stranded DNA or double-stranded DNA. The proposed fluorescence detection approach gives a wide linear range (500 pM-2 μM) and a low detection limit (500 pM) to sense H5N1 gene sequence. Furthermore, selective analysis of target DNA shows that our constructed analytical strategy has a high selectivity to H5N1 gene sequence. It is regarded as a promising method for highly sensitive and selective sensing of H5N1 virus.

A versatile low-temperature molten salt approach has been developed for fabricating a MoS2@CoS2 heterostructure electrocatalyst, where low-cost molten KSCN serves as both the reaction medium and sulfur source. The as-obtained electrocatalyst with a defect-rich structure is highly efficient for the hydrogen evolution reaction (HER), delivering a low overpotential of 96 mV at an HER current density of 10 mA cm-2, a small Tafel slope of 60 mV dec-1, and outstanding durability. Density functional theory (DFT) calculations suggest that the heterostructures present an optimized Gibbs free energy of hydrogen adsorption (ΔGH*) close to zero, which is responsible for the excellent HER performance.

Cobalt ion modified titanate nanoarray (CTO NA) with a three-dimensional hierarchical structure is synthesized via a facile ion exchange strategy and further developed as an electrocatalyst toward ...

A coral-like metallic Sn nanostructure was synthesized towards an advanced Li-ion battery anode via a facile one-pot displacement reaction. In the presence of 5 wt% sodium carboxymethyl cellulose and 5 wt% graphene oxide as a binary binder, the electrode demonstrates extraordinary Li storage behaviors in terms of high initial coulombic efficiency (68.7%), long-cycling life (800 cycles with a retention capacity of 422 mA h g-1 at 500 mA g-1), and superb rate capability. The fascinating electrochemical performance could be attributed to the 3D interconnected nanostructure together with the binary binder to ease the volume expansion of Sn.

Developing high-efficiency electrocatalysts for the hydrogen evolution and oxidation reactions (HER/HOR) in alkaline electrolytes is of critical importance for realizing renewable hydrogen technologies. Ruthenium phosphides (RuP

Potassium-ion batteries (PIBs) are attracting increasing attention due to the abundance of K resources, but the sluggish kinetics and inferior cycling stability of anodes still hinder their application. Herein, we present a hybrid 1T/2H phase MoSe

A low-temperature doping approach has been developed for fabricating nitrogen and sulfur co-doped few-layer graphene (NS-FLG) by annealing graphene oxide in KSCN molten salt at 175 °C. The as-prepared NS-FLG with a high doping level and unique few-layer structure delivers remarkable performance for sodium-ion batteries (SIBs) in terms of a high reversible capacity of 325.4 mA h g-1 at 0.5 A g-1, a superb rate capacity of 203.6 mA h g-1 at 10 A g-1, and ultra-long cyclability over 5100 cycles. This work provides a new avenue for exploring advanced graphene-based materials towards SIBs and even other electrochemical fields.

Li-chalcogen batteries, especially the Li-S batteries (LSBs), have received paramount interests as next generation energy storage techniques because of their high theoretical energy densities. However, the associated challenges need to be overcome prior to their commercialization. Elemental selenium, another chalcogen member, would be an attractive alternative to sulfur owing to its higher electronic conductivity, comparable capacity density, and moreover, excellent compatibility with carbonate electrolytes. Unlike LSBs, the research and development of Li-Se batteries (LSeBs) have garnered burgeoning attention but are still in their infant stage, where a comprehensive yet in-depth overview is highly imperative to guide future research. Herein, a critical review of LSeBs, in terms of the underlying mechanisms, cathode design, blocking layer engineering, and emerging solid-state electrolytes is provided. First, the electrolyte-dependent electrochemistry of LSeBs is discussed. Second, the advances in Se-based cathodes are comprehensively summarized, especially highlighting the state-of-the-art Sex Sy cathodes, and mainly focusing on their structures, compositions, and synthetic strategies. Third, the versatile separators/interlayers optimization and interface regulation are outlined, with a particular focus on the emerging solid-state electrolytes for advanced LSeBs. Last, the remaining challenges and research orientations in this booming field are proposed, which are expected to motivate more insightful works.

A versatile low-temperature molten salt approach has been developed for fabricating a MoS2@CoS2 heterostructure electrocatalyst, where low-cost molten KSCN serves as both the reaction medium and sulfur source. The as-obtained electrocatalyst with a defect-rich structure is highly efficient for the hydrogen evolution reaction (HER), delivering a low overpotential of 96 mV at an HER current density of 10 mA cm-2, a small Tafel slope of 60 mV dec-1, and outstanding durability. Density functional theory (DFT) calculations suggest that the heterostructures present an optimized Gibbs free energy of hydrogen adsorption (ΔGH*) close to zero, which is responsible for the excellent HER performance.

Borate ion-intercalated Ni Fe layered double hydroxide (Ni Fe LDH) is synthesized as a highly active electrocatalyst toward oxygen evolution reaction (OER) for the first time. With the intercalation of borate ions, the interlayer spacing and specific surface area of the Ni Fe LDH are increased, meanwhile the pore size distribution shifts to a larger pore size range. The borate ion-intercalated catalyst prepared at 20% of Fe content in presence of 0.05 M sodium borate additive exhibits the highest OER electrocatalytic activity, which shows a low onset overpotential of 270 mV and a Tafel slope of 42 mV dec−1. The high catalytic activity of intercalated OER catalyst can be attributed to the enhanced mass transport and charge transfer as well as the increased specific surface area due to the borate ion intercalation. In addition, the intercalated borate ions act as a proton-accepting agent help to promote O O bond formation during OER. This work would open up a novel strategy for the synthesis of ion-intercalated layered materials for high-performance water splitting applications.

A hybrid structure consisting of boron-doped porous carbon spheres and graphene (BPCS-G) has been designed and synthesized toward solving the polysulfide-shuttle problem, which is the most critical issue of current Li-S batteries. The proposed hybrid structure showing high surface area (870 m2·g−1) and high B-dopant content (6.51 wt.%) simultaneously offers both physical confinement and chemical absorption of polysulfides. On one hand, the abundant-pore structure ensures high sulfur loading, facilitates fast charge transfer, and restrains polysulfide migration during cycling. On the other hand, our density functional theory calculations demonstrate that the B dopant is capable of chemically binding polysulfides. As a consequence of such dual polysulfide confinement, the BPCS-G/S cathode prepared with 70 wt.% sulfur loading presents a high reversible capacity of 1,174 mAh·g−1 at 0.02 C, a high rate capacity of 396 mAh·g−1 at 5 C, and good cyclability over 500 cycles with only 0.05% capacity decay per cycle. The present work provides an efficient and cost-effective platform for the scalable synthesis of high-performance carbon-based materials for advanced Li-S batteries.

Layered γ-type iron oxyhydroxide (γ-FeOOH) is a promising material for various applications; however, its sheet-shaped structure often suffers from instability that results in aggregation and leads to inferior performance. Herein, a kinetically controlled hydrolysis strategy is proposed for the scalable synthesis of γ-FeOOH nanosheets arrays (NAs) with enhanced structural stability on diverse substrates at ambient conditions. The underlying mechanisms for the growth of γ-FeOOH NAs associated with their structural evolution are systematically elucidated by alkalinity-controlled synthesis and time-dependent experiments. As a proof-of-concept application, γ-FeOOH NAs are developed as electrocatalysts for the oxygen evolution reaction (OER), where the sample grown on nickel foam (NF) exhibits superior performance of high catalytic current density, small Tafel slope, and exceptional durability, which is among the top level of FeOOH-based electrocatalysts. Density functional theory calculations suggest that γ-NiOOH in situ generated from the electrooxidation of NF would induce charge accumulation on the Fe sites of γ-FeOOH NAs, leading to enhanced OER intermediates adsorption for water splitting. This work affords a new technique to rationally design and synthesize γ-FeOOH NAs for various applications.

Carbon materials are the commonly used catalyst supports for energy conversion and storage systems thanks to their high electronic conductivity and large specific surface area. Herein, hierarchical interconnected graphene oxide is synthesized using a facile thermally-induced expansion reduction approach, exhibiting a mainly direct pathway of four-electron transfer process toward oxygen reduction reaction. Compared to normal graphene oxide sheets, the hierarchical graphene oxide shows 38 mV more positive half-wave potential. It also shows remarkable methanol tolerance ability and better electrochemical stability than the commercial Pt/C. Its catalytic enhancement mechanism could be attributed to the architecture of interconnected hierarchical structure, which could offer appropriate distances for the bridge mode of oxygen adsorption. This work offers scientific insights on tailored graphene oxide nanostructures as an advanced electrocatalyst for fuel cells and beyond.

Electrochemical sensors involves electrocatalysis, which greatly relies on the surface electronic state of an electrode but often tedious or complicated surface modification toward a specific reaction. Here a facile electrochemical method is presented for the first time to directly tune Li1+xFePO4 for rich Li+ insertion to an elevated oxidation state for a highly sensitive nitric oxide (NO) sensor, in which the Li+-richest lithium iron phosphate (Li1.66FePO4, 7.3 wt%) over the pristine LiFePO4 (Li+ content of 4.5 wt%) is achieved, delivering a much higher sensitivity (90.38 vs 58.70 μA cm−2 μM−1) and a lower limit of detection (0.12 vs 3.10 nM) than the latter. The enhancement mechanism is investigated, indicating that high Li+ insertion in LiFePO4 rises the surface electronic structure for high oxidation state to strongly adsorb electronegative NO molecules and kinetically prompt the fast electron transfer toward NO oxidation. Additionally, a Li1.66FePO4 modified screen printed electrode was designed and fabricated to directly grow cells as unique sensing platform, by which the cell-released NO could be immediately captured for in situ real-time detection. This direct electrochemical tuning strategy significantly enhances sensing performance to accomplish the highest sensitivity (649.2 μA cm−2 μM−1) among all nonprecious material-based NO sensors while possessing universal significance to design various highly sensitive and selective electrochemical sensors.

Transition-metal disulfide with its layered structure is regarded as a kind of promising host material for sodium insertion, and intensely investigated for sodium-ion batteries. In this work, a simple solvothermal method to synthesize a series of MoS2 nanosheets@nitrogen-doped graphene composites is developed. This newly designed recipe of raw materials and solvents leads the success of tuning size, number of layers, and interplanar spacing of the as-prepared MoS2 nanosheets. Under cut-off voltage and based on an intercalation mechanism, the ultrasmall MoS2 nanosheets@nitrogen-doped graphene composite exhibits more preferable cycling and rate performance compared to few-/dozens-layered MoS2 nanosheets@nitrogen-doped graphene, as well as many other reported insertion-type anode materials. Last, detailed kinetics analysis and density functional theory calculation are also employed to explain the Na+ - storage behavior, thus proving the significance in surface-controlled pseudocapacitance contribution at the high rate. Furthermore, this work offers some meaningful preparation and investigation experiences for designing electrode materials for commercial sodium-ion batteries with favorable performance.

Herein for the first time we report a novel approach to prepare well-controlled iron phosphide nanorods (FeP NRs) via low-temperature phosphidation of Fe salt with a porous anodic aluminum oxide (AAO) template. The as prepared FeP NRs exhibit high catalytic activity toward hydrogen evolution reaction (HER) in acidic solutions, showing an onset potential of ∼45 mV, a Tafel slope of 55 mV/dec and nearly 100% Faradaic yield (FY) with good stability. Additionally, the catalyst can deliver current density of 2 and 10 mA/cm 2 for HER with low overpotentials of 67 and 120 mV, respectively. Up to date the FeP NRs should be the inexpensive electrocatalyst while offering high activity toward HER, thus holding a great promise for practical applications for water electrolysis in large scale production.

A novel tungsten diphosphide nanorods (WP2 NRs) material with good crystallinity is synthesized as an efficient hydrogen evolution reaction (HER) electrocatalyst for the first time through phosphidation of (NH4)0.25WO3 NRs precursor. Towards HER the WP2 NRs exhibit an onset overpotential of 56 mV, a Tafel slope of 52 mV per decade and an exchange current density of 0.013 mA cm−2 in acidic media. Further, the catalyst only needs overpotentials of 101 and 148 mV to deliver current densities of 2 and 10 mA cm−2, respectively. In particular, the catalyst can maintain its catalytic activity for 90 h at least, showing good long term operation stability. It also has excellent activity and stability under both neutral and basic conditions. The catalysis mechanism of WP2 NRs is explored for the fundamental insights.

For the first time, self-supported FeP nanorod arrays were developed on a HCl-treated Ti foil (FeP NAs/Ti) via low-temperature phosphidation of α-FeO(OH)/Ti precursor and were further used as a novel hydrogen evolution cathode (HER), demonstrating exceptional catalytic activity in acidic media, superior to all reported non-Pt HER electrocatalysts, while offering an innovative method to synthesize metal phosphides with well-controlled nanostructure and morphology.

For the first time, we demonstrate a template-assisting synthesis to make CoP nanotubes (CoP NTs) through low-temperature phosphidation of Co salt inside a porous anodic aluminium oxide template followed by dilute HF etching. Such CoP NTs exhibit excellent hydrogen-evolution catalytic activity and durability in an acidic medium, which is superior to their nanoparticle counterparts, with a Faradaic yield of nearly 100%. The fundamental insight for the catalytic enhancement mechanism is also explored.

Catalyst nanoparticles with enriched atomic steps structure can offer higher catalytic performance. Nevertheless, the reported sizes of PtCu nanoparticles with enriched atomic steps surface are usually larger than 30 nm or even hundreds of nanometres, which need great reduction for further improved catalytic performance. In this work, Pd nanocubes are used as seeds for mediating growth of 13.7 nm Pd@PtCu concave octahedrons with enriched atomic steps surface. Towards oxygen reduction reaction, the specific activity at 0.9 V for the Pd@PtCu concave octahedral catalyst is 3.36 mA cm-2 Pt, which is 2.6 and 11.4 times higher than that of Pd@PtCu octahedron (1.31 mA cm-2 Pt) and commercial Pt/C (0.29 mA cm-2 Pt) catalyst, respectively. The dramatic performance enhancement can be ascribed to the reduced particle sizes for increased electrochemically active surface area (ECSA), a high density of atomic steps and a large number of concave sites as highly active catalytic reaction centers to break O–O bonds. This work demonstrates a new approach to synthesize a superior electroactive catalyst, holding a great promise for practical applications in high-performance and low-temperature fuel cells.

Herein, a surfactant- and additive-free strategy is developed for morphology-controllable synthesis of cobalt pyrophosphate (CoPPi) nanostructures by tuning the concentration and ratio of the precursor solutions of Na4 P2 O7 and Co(CH3 COO)2 . A series of CoPPi nanostructures including nanowires, nanobelts, nanoleaves, and nanorhombuses are prepared and exhibit very promising electrocatalytic properties toward the oxygen evolution reaction (OER). Acting as both reactant and pseudo-surfactant, the existence of excess Na4 P2 O7 is essential to synthesize CoPPi nanostructures for unique morphologies. Among all CoPPi nanostructures, the CoPPi nanowires catalyst renders the best catalytic performance for OER in alkaline media, achieving a low Tafel slope of 54.1 mV dec-1 , a small overpotential of 359 mV at 10 mA cm-2 , and superior stability. The electrocatalytic activities of CoPPi nanowires outperform the most reported non-noble metal based catalysts, even better than the benchmark Ir/C (20%) catalyst. The reported synthesis of CoPPi gives guidance for morphology control of transition metal pyrophosphate based nanostructures for a high-performance inexpensive material to replace the noble metal-based OER catalysts. MOE (Min. of Education, S’pore)

For the first time we demonstrate the topotactic synthesis of a three-dimensional (3D) interconnected network of nanoporous CoP nanowires directly on a Ti substrate (np-CoP NWs/Ti) via low-temperature phosphidation of a Co2(OH)2(CO3)2/Ti precursor and its further use as a highly efficient hydrogen evolution cathode.