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Construction of gamma-phase transition metal oxyhydroxides for electrode materials is an effective strategy for improving electrochemical properties. However, the preparation of gamma-phase transition metal oxyhydroxides with various defects remains an arduous challenge. Herein, gamma-phase Ni–Co oxyhydroxides with cationic vacancy defects and crystalline–amorphous interfaces are synthesized successfully via electrochemical reconstruction to achieve an ultrahigh mass/areal/volumetric energy density, flexible all-solid-state asymmetric supercapacitor (ASC). The Ni–Co oxyhydroxides consist of γ-NiOOH, γ-CoOOH and NiOOH phases; the γ-NiOOH and γ-CoOOH phases can effectively improve electronic conductivity and theoretical capacitance due to the abundant Ni4+/Co4+. The cationic vacancy defects and crystalline–amorphous interfaces not only endow the gamma-phase Ni–Co oxyhydroxides with abundant electrochemical active sites, but also enable fast electron transfer between the electrode and electrolyte. Therefore, the as-obtained gamma-phase Ni–Co oxyhydroxides display a high capacitance of 20.9 F cm−2 at 4 mA cm−2 and 3483 F g−1 at 0.67 A g−1, as well as excellent rate characteristics (90.5% capacitance retention at a high current density of 240 mA cm−2 and 40 A g−1). Density functional theory calculations reveal that Ni–Co oxyhydroxides with cationic vacancies can increase the adsorption energy of H2O, which is beneficial for the capture of H2O to occur for subsequent charge storage reactions. Furthermore, the assembled Ni–Co oxyhydroxides//active carbon all-solid-state ASC shows ultrahigh mass/areal/volumetric energy density of 92.6 W h kg−1/3.3 mW h cm−2/19.5 mW h cm−3 (at 1156 W kg−1/34.6 mW cm−2/204.1 mW cm−3) and possesses excellent electrochemical stability with 91% retention after 7000 cycles. [ABSTRACT FROM AUTHOR]

As a green and renewable material, biomass-based carbon is one of the prospective electrode materials for supercapacitors. Limited by their microstructure and composition, the activation of biomass-based materials is challenging for enhancing the performance of supercapacitors. Herein, a series of porous carbon-based supercapacitor electrode materials have been synthesized via pyrolysis combined with KOH activation using the biomass waste of soybean pods as the carbon source. Theoretical calculation results proved that doping with N can improve the conductivity and K+-adsorption capacity or carbon materials, which can further improve their capacitive performance. O and N co-doped porous carbon with an optimal KOH content and operation temperature showed a large specific surface area (SSA) of 1807.56 m2 g−1, with a large capacitance of 366.1 F g−1 at 1 A g−1 and a great rate capability of 65.6% capacitance retention at 100 A g−1 (240 F g−1). In addition, the all-solid-state symmetric supercapacitor assembled using O and N co-doped porous carbon exhibits an energy density of 8.34 W h kg−1 at 247.95 W kg−1 with an excellent cycling stability of 96.03% capacity retention over 50 000 cycles. This work provides a new approach for the synthesis of biomass-based carbon materials, which can be used for energy-storage and -conversion applications. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride (PCN) is an emerging metal-free photocatalyst with high stability but is plagued by low photocatalytic efficiency due to the rapid charge carrier recombination behavior. Herein, Bi-doped graphitic carbon nitride nanotubes (BCN nanotubes) with a porous structure have been facilely prepared by one-step thermal polymerization of mixtures of melamine, urea and bismuth nitrate pentahydrate under an Ar atmosphere. With unique structural advantages for charge carrier transfer, light harvesting, and large surface area, the as-prepared BCN nanotubes exhibit excellent photocatalytic activity for the degradation of Rhodamine (Rh) B with a 26.8-fold higher reaction rate than that of PCN under visible light irradiation. This work provides informative principles about the synthesis of PCN with controlled morphology and element doping simultaneously for the photocatalytic degradation of chemical pollutants. [ABSTRACT FROM AUTHOR]

Photocatalytic nitrogen fixation is a desirable approach to future sustainable nitrogen conversion and might be considered as a potential alternative to the traditional Haber–Bosch process. However, the activation of nitrogen molecules and the complicated nitrogen fixation reaction process have remained grand challenges. Herein, we report an efficient photocatalyst, which was constructed by anchoring plasmonic gold nanocrystals on Mo doped W18O49 nanowires (denoted as Au-MWO). In addition to Mo doping improving N2 adsorption and activation, the anchored Au nanocrystals not only extend light absorption to generate energetic electrons, but also decrease the desorption energy of the NH3, which facilitates the release of active sites and further improves the catalytic reaction of nitrogen fixation. Due to the synergistic effect of Mo doping and Au nanocrystal loading, the plasmonic Au-MWO shows an apparent quantum efficiency of 0.611% at 540 nm and a high ammonia synthesis rate of 399.24 μmol g−1 h−1. This work offers a promising alternative route for designing efficient catalysts and brings fresh insights into the role of plasmonic noble metals in photocatalysts toward nitrogen fixation. [ABSTRACT FROM AUTHOR]

The inferior separation efficiency of photo-induced carriers is still a major obstacle to the practical application of photocatalysts, whereas the spatial separation of reductive and oxidative components is expected to break through this bottleneck to promote charge separation and surface reaction kinetics. Herein, Mo2C nanosheets were employed to prepare a Mo2C/MoS2/In2S3 dual-heterojunction (a p–n junction of MoS2/In2S3 and a Schottky junction of Mo2C/In2S3) by one-pot solvothermal synthesis. Theoretical and experimental results proved that Mo2C acted as an electron transport "highway" and acceptor in Mo2C/MoS2/In2S3 dual-heterojunctions to expedite the spatial migration of electrons. Compared with In2S3 and MoS2/In2S3, the optimized Mo2C/MoS2/In2S3 composite exhibited significantly improved photocatalytic property, with the Cr(VI) reduction efficiency reaching 99.1% in 90 min under visible light irradiation. This study demonstrates that Mo2C may play a major role in an electron sink that can be used as a potential co-catalyst in multijunctional photocatalysts. [ABSTRACT FROM AUTHOR]

Tailoring the d-band center is an effective method to promote the hydrogen evolution reaction (HER) activity of electrocatalysts. Herein, we demonstrate that the d-band center can be tuned through a hole-creating method to enhance pH-universal HER activity using CoP as a basic platform. The density functional theory (DFT) calculation reveals that the d-band center and the valence electron number of Co sites around the holes are upshifted, which boosts H adsorption. In addition, introducing holes into the nanosheets of CoP can optimize the ΔGH* of the Co atoms around the holes. Inspired by the DFT results, a soft template method was developed to synthesize hole-rich CoP nanosheets. With the advantages of hole-rich and unique nanosheet features, the hole-rich CoP nanosheets show low HER overpotentials with only 84 and 94 mV to achieve a current density of 10 mA cm−2 in both acidic and alkaline media, better than that of the other dimensional counterparts. In addition, the hole-rich CoP nanosheets also show satisfactory stability after long-term HER tests. This strategy of regulating the d-band center is expected to be extended to other transition metal phosphide electrocatalysts for enhancing the HER performance. [ABSTRACT FROM AUTHOR]

Electrically addressable covalent immobilization of probes on a multiplexed electrode for the simultaneous detection of multiple targets within the same sample is often regarded as a difficult milestone to be achieved. Herein, we demonstrated a reagentless disposable multiplexed electrochemical DNA and aptamer-based sensing platform for the simultaneous determination of various targets. The electrochemically triggered "click" chemistry was developed, and three biomarkers, including p53, thrombin, and VEGF165 were used as model analytes. The proposed sensor consisted of three independent screen-printed carbon electrodes (SPCE), with an alkyne–azide cycloaddition reaction that was activated selectively by means of electrical triggering, so that different DNA probes can be modified on the desired electrode units in sequence. In terms of simultaneous detection, the sensor was able to quantify the DNA target of p53 with a detection limit of 0.35 nM, whereas the limits of detection for protein quantification of thrombin and VEGF165 were 0.22 nM and 0.014 nM, respectively. The proposed sensor not only showed encouraging reproducibility and stability, but also performed well even in 50% serum samples. Therefore, the work described here offers a general strategy for developing a multiplexed sensor with promising potential to achieve rapid, simple and cost-effective analysis of biological samples. [ABSTRACT FROM AUTHOR]

Here, we report simple one-step solution phase synthesis for face-centered tetragonal FePtCu nanoparticles (NPs). Cu atoms are doped into the FePt lattice during synthesis, occupying Fe sites to form FePtCu alloy NPs. The phase and magnetic properties of the NPs can then be altered by varying the reaction conditions. We report room-temperature coercivities as high as 5.09 kOe for FePtCu NPs synthesized at 310 °C, significantly higher than the coercivity of pure FePt NPs without Cu doping. We suggest that Cu incorporation into the FePt lattice is responsible for the observed ordering enhancement of the as-prepared NPs, specifically increasing atomic diffusivity during the fcc-to-fct phase transformation. Our findings provide critical insights the effects Cu doping, namely its role in inducing atomic rearrangement and phase transformation of FePt NPs at low synthesis temperatures. [ABSTRACT FROM AUTHOR]

Core–shell architecture coupled with rational surface engineering constitutes an efficient strategy for promoting electrocatalysis on multimetallic nanocrystals via the optimization of composition, facets and coordination environment. Here, by leveraging controlled surface segregation, we realize core–shell formation with systematic tuning of surface composition on well-defined PdCuRu nanocrystals. When applied for the hydrogen evolution reaction (HER), we established a direct correlation between surface composition and activity. In particular, PdCuRu catalysts with a Pd-rich surface achieved an overpotential of 31 mV at a current density of 10 mA cm−2 and a low Tafel slope of 52 mV dec−1 in an alkaline electrolyte, considerably enhanced relative to control PdCuRu/C catalysts with other surface compositions and even exceeding those of state-of-the-art Pt/C. Similar trends were also observed in both neutral and acid electrolytes. We deduce that, in this catalytic system, the enhanced electrocatalysis originates from the strain effect rather than the bifunctional mechanism. The present study builds a bridge between surface engineering and HER performance, and opens up new material designs for surface Pd-rich core–shell nanostructures for the purpose of improving HER catalytic activity and stability at all pH values. [ABSTRACT FROM AUTHOR]

A new fluorescent supramolecular self-assembly gelator (1) based on naphthalimide derivative with a tetrazole group was designed and synthesized, which could form a stable gel in acetone/H2O (1/1, v/v). The self-assembly process of gelator 1 was studied through SEM, UV-Vis absorption, fluorescence emission, XRD, and water contact angle. The microbelt structure was observed for the self-assembly system with its hydrophobic surface with the contacting angle of 143°. J-type aggregation mode was employed in the gel state, whose fluorescence emission showed a large red-shift of 153 nm compared with that for the solution state. This self-assembly system could selectively detect Cu2+ and K+, and their corresponding limit of detection was 5.65 × 10−7 M and 1.73 × 10−7 M, respectively. it's the fluorescence emission and color changed during the detection process of K+. This self-assembly was immune to acid although it has a tetrazole group. Interestingly, this self-assembly system could continuously respond to the organic amine and gaseous acid in three different states such as solution, gel, and xerogel. The limit of detection in the solution state for TEA and TFA was 7.66 × 10−5 M and 2.01 × 10−7 M, respectively. The limit of detection of the xerogel film towards TEA was 0.19 ppm. This research will provide a new way for the construction of multifunctional self-assembly systems for the detection of metal ions or organic amines and gaseous acids. [ABSTRACT FROM AUTHOR]

An organic polymer photocatalyst (p-P) was designed and synthesized through Knoevenagel condensation between terephthalaldehyde and p-phenylenediacetonitrile with a high yield. The orange p-P polymer could emit pink light at 629 nm under excitation at 371 nm with a luminescence quantum yield of 2.57%. A cellular structure stacked by irregular polymer blocks was found in the p-P polymer with a small BET surface area of about 48.4 m2 g−1. p-P polymer was thermally stable up to 400 °C and possessed high charge separation efficiency and low resistance in charge transportation. DFT calculation and electrochemical experimental results indicated that the reduction reaction of water over the polymer is thermodynamically feasible. p-P polymer could efficiently split water under visible light irradiation with a prominent H2 production rate of up to 96.7 μmol g−1 h−1 and a TON of about 22.0. Our work provides a new strategy to build multifunctional conjugated polymers for efficient photocatalysis. [ABSTRACT FROM AUTHOR]

The photoelectrochemical (PEC) water splitting efficiency of a photoanode is restricted by charge recombination and sluggish reaction kinetics. Here, we demonstrated the spatial engineering of an ultrathin Co(OH)x encapsulated p-Cu2S/n-BiVO4 photoanode for simultaneously enhancing charge separation and surface reaction kinetics in solar water splitting. Specifically, the separation efficiency of photoexcited charge carriers in the bulk was effectively improved due to the formation of a p-Cu2S/n-BiVO4 heterojunction, and the light-driven water oxidation reaction on the surface was further promoted because of the introduction of Co(OH)x as an oxygen evolution catalyst (OEC) layer. As a result, the p-Cu2S/n-BiVO4 heterostructure yielded a largely enhanced charge separation efficiency of up to 79%, and a significant surface charge separation of 70% was achieved, attributed to the deposition of the Co(OH)x cocatalyst. Furthermore, this synergistic effect in the photoanode gave rise to a remarkably enhanced photocurrent density of 3.51 mA cm−2 at 1.23 V vs. the reversible hydrogen electrode. This spatial engineering provides an efficient strategy for the simultaneous improvement of internal and surface charge separation via dual modification, i.e., p–n heterojunction formation and OEC coating. [ABSTRACT FROM AUTHOR]

Herein, we report the production of a superior Mott–Schottky heterojunction that is based on PdAg nanowires (NWs) that grow in situ on graphitic carbon nitride (g-C3N4). Due to the strong Mott–Schottky effect between PdAg NWs and g-C3N4, the heterojunction enhances the photocatalytic dehydrogenation of formic acid (FA) (TOF = 420 h−1) without additives and under visible light (λ ＞ 400 nm) at 25 °C, which is the best value among all heterogeneous catalysts reported for the photocatalytic dehydrogenation of FA. The H2 production rate is almost constant under the current reaction conditions. Detailed studies reveal that a favorable charge transfer from g-C3N4 and Ag to Pd makes Pd electron-rich, which enhances the catalytic activity and stability of the heterojunction for the photocatalytic dehydrogenation of FA under visible light. Our studies open up a new route to the design of a metal–semiconductor heterojunction for visible light-driven photocatalytic dehydrogenation of FA. [ABSTRACT FROM AUTHOR]

The demand for nylon-66 has sharply increased in industry because of its high mechanical strength, high rigidity, and excellent stability. The deep hydrogenation of adiponitrile (ADN) to 1,6-hexanediamine (HDA) is considered as a crucial step to produce nylon-66 in industry. Herein, we report a diffusion strategy to prepare surface Pd-rich PdAg nanowires (NWs) via a seed-mediated growth in polyol solution for efficient dehydrogenation catalysis of formic acid (FA) and subsequent hydrogenation of ADN by using FA as an in situ hydrogen source. The composition of surface Pd-rich PdAg NWs could be easily tuned by controlling the amounts of the precursors. And the surface Pd-rich Pd5Ag5 NWs exhibit the highest activity for dehydrogenation catalysis of FA with an initial TOF of 1600 h−1 and a highly efficient hydrogenation of ADN to HDA with 99% selectivity and 99% conversion at 50 °C. Their enhanced catalytic performance could be attributed to the Pd-rich surface of the NWs and more efficient electron transfer from Ag to Pd. This work demonstrates a new way to prepare surface Pd-rich Pd5Ag5 NWs for deeply hydrogenating ADN to HDA with FA as an in situ hydrogen source. [ABSTRACT FROM AUTHOR]

Nitrate (NO3−) and nitrite (NO2−) pollution in water has increasingly become a serious environmental concern. The catalytic reduction of NO3− and NO2− to harmless N2 by a reducing agent is considered to be one of the most promising methods to remove NO3− and NO2− from water. Herein, we report the one-pot synthesis of networked Ag/AgPd core/shell nanowires (CS-NWs) via seed-mediated growth in polyol solution. The shell thickness of the networked Ag/AgPd CS-NWs can be readily controlled by tuning the amount of precursors. The networked Ag/AgPd CS-NWs with a 0.9 nm shell thickness exhibited the highest activity towards the dehydrogenation catalysis of FA with an initial TOF of 1400 h−1 at 50 °C, and the highest selectivity for the catalysis of NO3− and NO2− to N2 in water and at room temperature. Their enhanced bifunctional catalytic performance could be attributed to more efficient electron transfer from PVPI and Ag to Pd. This work demonstrates a new way to prepare bifunctional nanocatalysts for the removal of NO3− and NO2− from water using FA as the in situ hydrogen source. [ABSTRACT FROM AUTHOR]

The electronic structure tuning of heterogeneous nanocatalysts is considered as one of the most effective ways of enhancing the catalytic activity of different chemical reactions. Herein, we demonstrate an effective way of tuning the electronic structure of networked PdAg nanowires (NWs) using polyvinylpyrrolidine imine (PVPI) as a new ligand to achieve more efficient hydrogen generation from formic acid (FA) decomposition. The PVPI-capped Pd5Ag5 NWs show the highest activity for the dehydrogenation catalysis of FA with an initial turnover frequency (TOF) of 242 h−1 among all the reported catalysts, and an increased TOF of 312 h−1 under 365 nm light irradiation at room temperature. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies reveal that there is an interfacial electron transfer from PVPI to the PdAg NW surface, which is the key factor in boosting the dehydrogenation catalysis of FA herein. Density functional theory calculations suggest that the high catalytic activity primarily stems from both electronegative Pd active centers and the imino group (C=N) in PVPI for efficiently deprotonating FA to Pd-formate intermediates and subsequently for promoting the cleavage of C–H. The PVPI-capped Pd5Ag5 NWs are very stable and reusable for FA dehydrogenation catalysis. [ABSTRACT FROM AUTHOR]

We report a novel approach for the fabrication of exchange-coupling L10-FePt–bcc-Fe nanocomposites with a gradient interface between hard and soft phases from FePt nanoparticles (NPs) and FePt–Fe3O4 dumbbell shaped NPs, which are prepared by a facile one-pot synthesis method. High temperature annealing in argon is first used to convert FePt in FePt–Fe3O4 dumbbell shaped NPs to the L10-FePt phase. Then Fe3O4 in FePt–Fe3O4 dumbbell shaped NPs is reduced to bcc-Fe by low temperature annealing in reducing gas, forming L10-FePt–Fe nanocomposites. The L10-FePt–Fe nanocomposites exhibit both large coercivity and high magnetic moment. The work demonstrates that creating a nanoscale gradient interface between magnetically hard and soft phases is a promising approach for the fabrication of high performance permanent magnets. [ABSTRACT FROM AUTHOR]