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Electrochemical conversion of nitrate to ammonia offers an efficient approach to reducing nitrate pollutants and a potential technology for low-temperature and low-pressure ammonia synthesis. However, the process is limited by multiple competing reactions and NO3− adsorption on cathode surfaces. Here, we report a Fe/Cu diatomic catalyst on holey nitrogen-doped graphene which exhibits high catalytic activities and selectivity for ammonia production. The catalyst enables a maximum ammonia Faradaic efficiency of 92.51% (−0.3 V(RHE)) and a high NH3 yield rate of 1.08 mmol h−1 mg−1 (at − 0.5 V(RHE)). Computational and theoretical analysis reveals that a relatively strong interaction between NO3− and Fe/Cu promotes the adsorption and discharge of NO3− anions. Nitrogen-oxygen bonds are also shown to be weakened due to the existence of hetero-atomic dual sites which lowers the overall reaction barriers. The dual-site and hetero-atom strategy in this work provides a flexible design for further catalyst development and expands the electrocatalytic techniques for nitrate reduction and ammonia synthesis. Nitrate electroreduction to ammonia can decrease pollutants and produce high-value ammonia. Here, the authors design a Fe/Cu diatomic catalyst on nitrogen-doped graphene, which exhibits high catalytic activities of and selectivity for ammonia. [ABSTRACT FROM AUTHOR]

Video has become one of the main ways of information transmission with the development of the Internet. Video copyright protection becomes an urgent task. Video watermark technology embeds copyright into the redundant information of the carrier, and video copyright protection is achieved. However, most video watermark algorithms do not use the correlation and redundancy among adjacent frames of a video and are weak to resist frame attacks. In order to make up this shortage and improve robustness, a video watermark algorithm based on a tensor feature map is proposed. A grayscale video segment with the same scene is selected and represented as a 3-order tensor, a high-order singular value decomposition is performed on the video tensor to obtain a stable core tensor and three factor matrices. A feature tensor is obtained by the mode-3 product of the video tensor with the transpose of the factor matrix that contains a time axis. It is called a tensor feature map. Since the tensor feature map contains the main information of each frame of a video, the watermark is distributed in each frame of a video by embedding the watermark into the tensor feature map. The first-order discrete wavelet transform and discrete cosine transform are used to embed the watermark into the tensor feature map. The experimental results show that the proposed watermark algorithm based on the tensor feature map has better transparency and is robust to common video attacks. [ABSTRACT FROM AUTHOR]

Highlights: The state-of-the-art development in electrochemical H2O2 production via the two-electron oxygen reduction reaction is reviewed with emphasis on material science, reaction mechanisms, and fundamental factors that govern the reaction route. General principles and strategies for catalyst design are summarized to understand the inherent relationships between the catalyst properties and electrocatalytic performances. Perspectives and challenges are presented to get insights into the large-scale manufacturing of H2O2 via the electrochemical routes. An environmentally benign, sustainable, and cost-effective supply of H2O2 as a rapidly expanding consumption raw material is highly desired for chemical industries, medical treatment, and household disinfection. The electrocatalytic production route via electrochemical oxygen reduction reaction (ORR) offers a sustainable avenue for the on-site production of H2O2 from O2 and H2O. The most crucial and innovative part of such technology lies in the availability of suitable electrocatalysts that promote two-electron (2e–) ORR. In recent years, tremendous progress has been achieved in designing efficient, robust, and cost-effective catalyst materials, including noble metals and their alloys, metal-free carbon-based materials, single-atom catalysts, and molecular catalysts. Meanwhile, innovative cell designs have significantly advanced electrochemical applications at the industrial level. This review summarizes fundamental basics and recent advances in H2O2 production via 2e–-ORR, including catalyst design, mechanistic explorations, theoretical computations, experimental evaluations, and electrochemical cell designs. Perspectives on addressing remaining challenges are also presented with an emphasis on the large-scale synthesis of H2O2 via the electrochemical route. [ABSTRACT FROM AUTHOR]

Highlights: Cyclohexanedodecol (CHD) could facilitate the Zn dendrite-free plating/stripping at a nanoscale. The CHD molecules could effectively modify the hydrated Zn(H2O)62+ structure in aqueous Zn ion batteries. The addition of CHD could establish robust protection layers on the Zn electrode surface. The CHD-modified electrolytes exhibit long-term cycling stability. Aqueous zinc-ion batteries (AZIBs) can be one of the most promising electrochemical energy storage devices for being non-flammable, low-cost, and sustainable. However, the challenges of AZIBs, including dendrite growth, hydrogen evolution, corrosion, and passivation of zinc anode during charging and discharging processes, must be overcome to achieve high cycling performance and stability in practical applications. In this work, we utilize a dual-functional organic additive cyclohexanedodecol (CHD) to firstly establish [Zn(H2O)5(CHD)]2+ complex ion in an aqueous Zn electrolyte and secondly build a robust protection layer on the Zn surface to overcome these dilemmas. Systematic experiments and theoretical calculations are carried out to interpret the working mechanism of CHD. At a very low concentration of 0.1 mg mL−1 CHD, long-term reversible Zn plating/stripping could be achieved up to 2200 h at 2 mA cm−2, 1000 h at 5 mA cm−2, and 650 h at 10 mA cm−2 at the fixed capacity of 1 mAh cm−2. When matched with V2O5 cathode, the resultant AZIBs full cell with the CHD-modified electrolyte presents a high capacity of 175 mAh g−1 with the capacity retention of 92% after 2000 cycles under 2 A g−1. Such a performance could enable the commercialization of AZIBs for applications in grid energy storage and industrial energy storage. [ABSTRACT FROM AUTHOR]

A traditional image steganography embeds secret information into a cover image to generate a secret-embedded image. The modification traces imposed on the cover image can be easily detected by steganalysis tools. Coverless steganography has been introduced to solve this problem. In this study, coverless steganography is combined with image style transfer, an arbitrary image style transfer network CSST-Net is put forward, and a secret information is encoded into the parameters (an adaptive steganography matrix) of CSST-Net, which is used to restrict the style transfer. Arbitrary image style transfer is performed instructed by the adaptive steganography matrix, and the image style transfer result driven by secret information is directly synthesized. Our experiments show that CSST-Net can not only synthesize any image style transfer result with good visual effect, but also achieve good performance in capacity, anti-steganalysis and security. [ABSTRACT FROM AUTHOR]

Highlights: Interface engineering of heterogeneous CoS/CoO nanocrystals and N-doped graphene composite facilitates high-performance oxygen reduction reaction and oxygen evolution reaction. Density functional theory calculations and experimental results confirm the enhanced electrocatalytic performances via the proposed interface engineering. The bifunctional oxygen electrocatalyst exhibits excellent performances in rechargeable Zn–air batteries. Low cost and green fabrication of high-performance electrocatalysts with earth-abundant resources for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for the large-scale application of rechargeable Zn–air batteries (ZABs). In this work, our density functional theory calculations on the electrocatalyst suggest that the rational construction of interfacial structure can induce local charge redistribution, improve the electronic conductivity and enhance the catalyst stability. In order to realize such a structure, we spatially immobilize heterogeneous CoS/CoO nanocrystals onto N-doped graphene to synthesize a bifunctional electrocatalyst (CoS/CoO@NGNs). The optimization of the composition, interfacial structure and conductivity of the electrocatalyst is conducted to achieve bifunctional catalytic activity and deliver outstanding efficiency and stability for both ORR and OER. The aqueous ZAB with the as-prepared CoS/CoO@NGNs cathode displays a high maximum power density of 137.8 mW cm−2, a specific capacity of 723.9 mAh g−1 and excellent cycling stability (continuous operating for 100 h) with a high round-trip efficiency. In addition, the assembled quasi-solid-state ZAB also exhibits outstanding mechanical flexibility besides high battery performances, showing great potential for applications in flexible and wearable electronic devices. [ABSTRACT FROM AUTHOR]

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Highlights: Comprehensive summary of crystalline structures and morphologies of carbon nitride-based materials (CNBMs). Density functional theory computation for the design of functional CNBMs for rechargeable battery applications. The experimental synthesis strategies of CNBMs for rechargeable battery application. Carbon nitrides (including CN, C2N, C3N, C3N4, C4N, and C5N) are a unique family of nitrogen-rich carbon materials with multiple beneficial properties in crystalline structures, morphologies, and electronic configurations. In this review, we provide a comprehensive review on these materials properties, theoretical advantages, the synthesis and modification strategies of different carbon nitride-based materials (CNBMs) and their application in existing and emerging rechargeable battery systems, such as lithium-ion batteries, sodium and potassium-ion batteries, lithium sulfur batteries, lithium oxygen batteries, lithium metal batteries, zinc-ion batteries, and solid-state batteries. The central theme of this review is to apply the theoretical and computational design to guide the experimental synthesis of CNBMs for energy storage, i.e., facilitate the application of first-principle studies and density functional theory for electrode material design, synthesis, and characterization of different CNBMs for the aforementioned rechargeable batteries. At last, we conclude with the challenges, and prospects of CNBMs, and propose future perspectives and strategies for further advancement of CNBMs for rechargeable batteries. [ABSTRACT FROM AUTHOR]

Electrolyte engineering is considered as an effective strategy to establish stable solid electrolyte interface (SEI), and thus to suppress the growth of lithium dendrites. In a recent study reported in Advanced Functional Materials by Ma group, discovered that strong coordination force could be founded between 15-Crown-5 ether (15-C-5) and Li+, which facilitates the crown ether (15-C-1) to participate in the solvation structure of Li+ in the electrolyte for the same purpose. Such a novel strategy might impact the design of high-performance and safe lithium metal batteries (LMBs). [ABSTRACT FROM AUTHOR]

A high-safety and low-cost route is important in the development of sodium-ion batteries, especially for large-scale stationary battery systems. An aqueous sodium-ion battery is demonstrated using a single NASICON-structured NaVTi(PO) material with the redox couples of V/V and Ti/Ti working on the cathode and anode, respectively. The symmetric full cell fabricated based on the bi-functional electrode material exhibits a well-defined voltage plateau at ∼1.2 V and an impressive cycling stability with capacity retention of 70% exceeding 1,000 cycles at 10C (1C = 62 mA·g). This study provides a feasible strategy for obtaining high-safety and low-cost rechargeable batteries using a single active material in aqueous media. [ABSTRACT FROM AUTHOR]

Due to its natural abundance, low cost and environmental sustainability, carbon derived from biomass has been widely utilized for energy storage and conversion. Herein, we report a facile strategy to synthesize a hierarchically porous carbon via the pyrolysis of seaweed biomass under inert atmosphere and apply it as a cathode material in lithium-sulfur (Li-S) batteries for the first time. Systematic materials characterization suggests that the seaweed carbon (SWC) is doped with N and displays micro-, meso- and macroporous structures and possesses a high total pore volume of 1.48 cm g and a high surface area of 1510.71 m g, which is beneficial for encapsulating a large amount of sulfur. The as-obtained SWC-S composite, containing 65.7 wt% sulfur content, delivered a high initial discharge capacity of 1221.2 mAh g and retained a capacity of 826.4 mAh g after 70 cycles at 0.2 C. Additionally, the SWC-S composite produced a reversible capacity of 540.6 mAh g after 300 cycles at high rate of 1 C. Compared to the pure sulfur cathode, the SWC-S cathode displays excellent rate capabilities, low polarization and good reaction kinetics, highlighting that this biomass-derived porous carbon is suitable for assembling high-performance Li-S batteries. [ABSTRACT FROM AUTHOR]

Concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were measured in water, sediments, Ceratophyllum (hornwort), and Bellamya sp. (edible snail) from residential, mixed (industrial and commercial), and agricultural areas with rural rivers in the Taihu Lake region, China. Zn concentrations were the highest, whereas Cd concentrations were the lowest among the six metals in water, sediments, and aquatic organisms. Cd was mainly present in the acid-soluble fraction, Cr in the residual fraction, and Pb in the reducible fraction of sediments. Heavy metal concentrations in water, sediments, and aquatic organisms in the three areas followed the order of the mixed area > residential area > agricultural area. Heavy metal concentrations in aquatic organisms were not only related to total metal concentrations in water and sediments but also to metal speciation concentrations in sediments. In addition, the bio-concentration factor (BCF) values of Cr, Cu, Pb, and Zn for Bellamya sp. were higher than those for Ceratophyllum, whereas the BCF values of Cd and Ni for Bellamya sp. were lower than those for Ceratophyllum. An ecological risk assessment of heavy metals in sediments showed that Cd posed the highest ecological risk to the environment. A health risk assessment showed that consuming Bellamya sp. from the mixed area could cause a potential health risk. [ABSTRACT FROM AUTHOR]

Being simple, inexpensive, scalable and environmentally friendly, microporous biomass biochars have been attracting enthusiastic attention for application in lithium-sulfur (Li-S) batteries. Herein, porous bamboo biochar is activated via a KOH/annealing process that creates a microporous structure, boosts surface area and enhances electronic conductivity. The treated sample is used to encapsulate sulfur to prepare a microporous bamboo carbon-sulfur (BC-S) nanocomposite for use as the cathode for Li-S batteries for the first time. The BC-S nanocomposite with 50 wt.% sulfur content delivers a high initial capacity of 1,295 mA·h/g at a low discharge rate of 160 mA/g and high capacity retention of 550 mA·h/g after 150 cycles at a high discharge rate of 800 mA/g with excellent coulombic efficiency (⩾95%). This suggests that the BC-S nanocomposite could be a promising cathode material for Li-S batteries. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Nanostructured semiconductors have been researched intensively for energy conversion and storage applications in recent decades. Despite of tremendous findings and achievements, the performance of the devices resulted from the nanomaterials in terms of energy conversion efficiency and storage capacity needs further improvement to become economically viable for subsequent commercialization. Hydrogenation is a simple, efficient, and cost-effective way for tailoring the electronic and morphological properties of the nanostructured materials. This work reviews a series of hydrogenated nanostructured materials was produced by the hydrogenation of a wide range of nanomaterials. These materials with improved inherent conductivity and changed characteristic lattice structure possess much enhanced performance for energy conversion application, e.g., photoelectrocatalytic production of hydrogen, and energy storage applications, e.g., lithium-ion batteries and supercapacitors. The hydrogenation mechanisms as well as resultant properties responsible for the efficiency improvement are explored in details. This work provides guidance for researchers to use the hydrogenation technology to design functional materials. [ABSTRACT FROM AUTHOR]

In this work, we report the use of a non-toxic nanocrystal CuO-loaded TiO nanotube array (CuO/TNTs) film as high-performance visible-light bactericidal photocatalyst. The samples were characterized by field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible diffusion reflection spectroscopy. This CuO/TNTs film photocatalyst is capable of complete inactivation of Escherichia coli in 5 × 10 colony-forming units/mL within a record short disinfection time of 20 min under visible-light irradiation. The average bactericidal percentage of the CuO/TNTs for E. coli under visible-light irradiation are 20 times and 6.6 times higher than those of TNTs under the same conditions and CuO/TNTs without light, respectively. This superior bactericidal performance is mainly attributed to the high ability to produce OH radicals by both photogenerated electron and hole of the prepared photocatalyst under visible light. The CuO/TNTs film photocatalyst makes it applicable to broad fields including drinking water disinfection. [ABSTRACT FROM AUTHOR]

Uniquely structured rutile TiO microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 °C for 2 h, the rutile TiO microspheres with a high surface area of 132 m/g have been utilized as a light harvesting enhancement material for dye-sensitized solar cells (DSSCs). The resultant DSSCs exhibit an overall light conversion efficiency of 8.41% for TiO photoanodes made of rutile TiO microspheres and anatase TiO nanoparticles (mass ratio of 1:1), significantly higher than that of pure anatase TiO nanoparticle photoanodes of similar thickness (6.74%). Such a significant improvement in performance can be attributed to the enhanced light harvesting capability and synergetic electron transfer effect. This is because the photoanodes made of rutile TiO microsphere possess high refractive index which improves the light utilisation efficiency, suitable microsphere core sizes (450-800 nm) to effectively scatter visible light, high surface area for dye loading, and synergetic electron transfer effects between nanoparticulate anatase and nano-acicular rutile single crystals phases giving high electron collection efficiency. [InlineMediaObject not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Four types of TiO thin-film electrodes were fabricated from TiO and Fe(III) doped TiO sols using a layer-by-layer dip-coating technique. Electrodes fabricated were TF (pure TiO surface, Fe(III)-TiO bottom layer), FT (Fe(III)-TiO surface, pure TiO bottom layer), TT (both layers pure TiO) and FF (both layers Fe(III)-TiO). The photoelectrochemical behavior of these electrodes was characterized using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and steady-state photocurrent measurements in aqueous 0.1 mol L NaNO containing varying concentrations of glucose or potassium hydrogen phthalate (KHP). EIS and LSV results revealed that exciton separation efficiency followed the sequence of TF > TT > FT > FF. Under a constant potential of +0.3 V, steady-state photocurrent profiles were recorded with varying organic compound concentrations. The TF electrode possessed the greatest photocatalytic capacity for oxidizing glucose and KHP, and possessed a KHP anti-poisoning effect. Enhanced photoelectrochemical performance of the TF electrode was attributed to effective exciton separation because of the layered TF structure. [ABSTRACT FROM AUTHOR]

Long-term stability and high-rate capability have been the major challenges of sodium-ion batteries. Layered electroactive materials with mechanically robust, chemically stable, electrically and ironically conductive networks can effectively address these issues. Herein we have successfully directed carbon nanofibers to vertically penetrate through graphene sheets, constructing robust carbon nanofiber interpenetrated graphene architecture. Molybdenum disulfide nanoflakes are then grown in situ alongside the entire framework, yielding molybdenum disulfide@carbon nanofiber interpenetrated graphene structure. In such a design, carbon nanofibers prevent the restacking of graphene sheets and provide ample space between graphene sheets, enabling a strong structure that maintains exceptional mechanical integrity and excellent electrical conductivity. The as-prepared sodium ion battery delivers outstanding electrochemical performance and ultrahigh stability, achieving a remarkable specific capacity of 598 mAh g−1, long-term cycling stability up to 1000 cycles, and an excellent rate performance even at a high current density up to 10 A g−1. Here the authors construct carbon nanofiber interpenetrated graphene architecture with in-situ grown MoS2 nanoflakes alongside the framework. The design combines exceptional mechanical integrity and excellent electronic conductivity, enabling outstanding electrochemical performance in sodium-ion battery. [ABSTRACT FROM AUTHOR]

Large-scale applications of rechargeable batteries consume nonrenewable resources and produce massive amounts of end-of-life wastes, which raise sustainability concerns in terms of manufacturing, environmental, and ecological costs. Therefore, the recyclability and sustainability of a battery should be considered at the design stage by using naturally abundant resources and recyclable battery technology. Herein, we design a fully recyclable rechargeable sodium ion battery with bipolar electrode structure using Na3V2(PO4)3 as an electrode material and aluminum foil as the shared current collector. Such a design allows exceptional sodium ion battery performance in terms of high-power correspondence and long-term stability and enables the recycling of ∼100% Na3V2(PO4)3 and ∼99.1% elemental aluminum without the release of toxic wastes, resulting in a solid-component recycling efficiency of >98.0%. The successful incorporation of sustainability into battery design suggests that closed-loop recycling and the reutilization of battery materials can be achieved in next-generation energy storage technologies. Effective recycling technologies represent a solution to the sustainability and environmental consequences of spent rechargeable batteries. Here, the authors show a bipolar electrode design that allows not only good electrochemical performance but a closed loop of material use for sodium ion batteries. [ABSTRACT FROM AUTHOR]

In the meta-universe scenario, with the development of personalized social networks, interactive behaviors such as uploading and sharing personal and family photographs are becoming increasingly widespread. Consequently, the risk of being searched or leaking personal financial information increases. A possible solution is to use anonymized face images instead of real images in the public situations. Most of the existing face anonymization methods attempt to replace a large portion of the face image to modify identity information. However, the resulted faces are often not similar enough to the original faces as seen with the naked eyes. To maintain visual coherence as much as possible while avoiding recognition by face recognition systems, we propose to detect part of the face that is most relevant to the identity based on saliency analysis. Furthermore, we preserve the identification of irrelevant face features by re-injecting them into the regenerated face. The proposed model consists of three stages. Firstly, we employ a dynamic identity perception network to detect the identity-relevant facial region and generate a masked face with removed identity. Secondly, we apply feature selection and preservation network that extracts basic semantic attributes from the original face and also extracts multilevel identity-irrelevant face features from the masked face, and then fuses them into conditional feature vectors for face regeneration. Finally, a pre-trained StyleGAN2 generator is applied to obtain a high-quality identity-obscured face image. The experimental results show that the proposed method can obtain more realistic anonymized face images that retain most of the original facial attributes, while it can deceive face recognition system to protect privacy in the modern digital economy and entertainment scenarios. [ABSTRACT FROM AUTHOR]