Ru doped NiMoO4 nanoarray as a high-efficiency electrocatalyst for nitrite reduction to ammonia.

The electrocatalytic reduction of nitrite to recyclable ammonia (NH3) is essential to maintain nitrogen balance and meet growing energy requirements. Herein, we report that Ru doped honeycomb NiMoO4 nanosheet with copious oxygen vacancies grown on nickel foam substrate has been prepared by a facile hydrothermal synthesis and immersion process, which can act as an efficient electrocatalyst for NH3 synthesis by reduction of nitrite. By optimizing the concentration of RuCl3 solution, 0.01Ru-NiMoO4/NF possesses excellent NO2-RR performance with NH3 yield of 20249.17 ± 637.42 µg h-1 cm-2 at -0.7 V and FE of 95.56 ± 0.72 % at -0.6 V. When assembled into a Zn-NO2- battery, it provides a remarkable level of power density of 13.89 mW cm-2, outperforming the performance of virtually all previous reports. The efficient adsorption and activation of NO2- over Ru-doped NiMoO4 with oxygen vacancy have been verified by density functional theory calculations, as well as the possible reaction pathway.

Internal Vanadium Doping and External Modification Design of P2-Type Layered Mn-Based Oxides as Competitive Cathodes toward Sodium-Ion Batteries.

P2-type layered manganese-based oxides have attracted considerable interest as economical, cathode materials with high energy density for sodium-ion batteries (SIBs). Despite their potential, these materials still face challenges related to sluggish kinetics and structural instability. In this study, a composite cathode material, Na0.67Ni0.23Mn0.67V0.1O2@Na3V2O2(PO4)2F was developed by surface-coating P2-type Na0.67Ni0.23Mn0.67V0.1O2 with a thin layer of Na3V2O2(PO4)2F to enhance both the electrochemical sodium storage and material air stability. The optimized Na0.67Ni0.23Mn0.67V0.1O2@5wt %Na3V2O2(PO4)2F exhibited a high discharge capacity of 176 mA h g-1 within the 1.5-4.1 V range at a low current density of 17 mA g-1. At an increased current density of 850 mA g-1 within the same voltage window, it still delivered a substantial initial discharge capacity of 112 mAh g-1. These findings validate the significant enhancement of ion diffusion capabilities and rate performance in the P2-type Na0.67Ni0.33Mn0.67O2 material conferred by the composite cathode.

NiMoO4 nanorods with oxygen vacancies self-supported on Ni foam towards high-efficiency electrocatalytic conversion of nitrite to ammonia.

As an eco-friendly and sustainable strategy, the electrochemical reduction of nitrite (NO2-) can simultaneous generation of NH3 and treatment of NO2- contamination in the environment. Herein, monoclinic NiMoO4 nanorods with abundant oxygen vacancies self-supported on Ni foam (NiMoO4/NF) are considered high-performance electrocatalysts for ambient NH3 synthesis by reduction of NO2-, which can deliver an outstanding yield of 18089.39 ± 227.98 µg h-1 cm-2 and a preferable FE of 94.49 ± 0.42% at -0.8 V. Additionally, its performance remains relatively stable during long-term operation as well as cycling tests. Furthermore, density functional theory calculations unveil the vital role of oxygen vacancies in promoting nitrite adsorption and activation, ensuring efficient NO2-RR towards NH3. A Zn-NO2- battery with NiMoO4/NF as the cathode shows high battery performance as well.

Copper-based catalysts for the electrochemical reduction of carbon dioxide: progress and future prospects.

There is an urgent need for the development of high performance electrocatalysts for the CO2 reduction reaction (CO2RR) to address environmental issues such as global warming and achieve carbon neutral energy systems. In recent years, Cu-based electrocatalysts have attracted significant attention in this regard. The present review introduces fundamental aspects of the electrocatalytic CO2RR process together with a systematic examination of recent developments in Cu-based electrocatalysts for the electroreduction of CO2 to various high-value multicarbon products. Current challenges and future trends in the development of advanced Cu-based CO2RR electrocatalysts providing high activity and selectivity are also discussed.

High Proportion of Active Nitrogen-Doped Hard Carbon Based on Mannich Reaction as Anode Material for High-Performance Sodium-Ion Batteries.

The potential for energy storage in carbonaceous materials is well known. Heteroatom doping - particularly nitrogen doping - can further enhance their electrochemical performance. The type of N configuration determines the reactivity of doped carbon. It remains a challenge, however, to achieve a high ratio of active N (N-5) in N-doped carbon. In this study, a high proportion of active nitrogen-doped hard carbon (PTA-Lys-800) is synthesized by the classical Mannich reaction, using tannic acid (TA) and amino acid as precursors. For sodium-ion batteries (SIBs), PTA-Lys-800 provides outstanding cycling stability and rate performance (338.8 mAh g-1 at 100 mA g-1 for 100 cycles, a capacity retention of 86 %; 131.1 mAh g-1 at 4 A g-1 after 5000 cycles). The excellent performance of PTA-Lys-800 is attributed to stable hierarchical pore structure, abundant defects, and a high proportion of N-5 formed during the carbonization process. Based on a detailed fundamental analysis, the pseudocapacitance mechanism is found to contribute to the higher sodium storage process in PTA-Lys-800. The Na-adsorption mechanism is further explored through ex situ Raman spectroscopy. A new method is presented for designing carbonaceous anode materials with high capacity and long cycle life.

Enhanced cycling stability and storage performance of Na0.67Ni0.33Mn0.67-xTixO1.9F0.1 cathode materials by Mn-rich shells and Ti doping.

We propose a synergistic strategy of titanium doping and surface coating with a Mn-rich shell to modify the Na-rich manganese-oxide-based cathode material Na0.67Ni0.33Mn0.67-xTixO1.9F0.1 in sodium-ion batteries and elucidate the underlying mechanism for enhanced material performance. First, it is found that the electrochemical performance of the proposed cathode material can be effectively improved when the Ti doping amount is x = 0.3. In addition to doping, the cathode material coated with a manganese-rich shell was prepared by a liquid coating method. The as-prepared Mn@Ti-doped-Na0.67Ni0.33Mn0.37Ti0.3O1.9F0.1 exhibited excellent electrochemical performance, delivering 169 mAh/g discharge capacity. The charge-discharge cycle test was carried out at a current density of 2C, and the sample not only provides a reversible capacity of 119 mAh/g but also has a capacity retention rate of 71 % after 500 charge-discharge cycles. The Ti doping and surface coating with a Mn-rich shell are shown to improve the specific discharge capacity, cycling stability and rate capability of the cathode material and mitigate voltage decay. These results validate our design principle and provide a novel approach to enhance the performance of cathode materials in sodium-ion batteries.

Poly tannic acid carbon rods as anode materials for high performance lithium and sodium ion batteries.

Due to abundant resources and low prices, biomass-derived carbons as anodes for lithium ion batteries (LIBs) and sodium ion batteries (SIBs) have been widely reported. However, it is still a challenge to design a biomass-derived carbon material that has immunity to environmental influences, stable chemical composition and controllable morphology. In this paper, tannic acid (TA) as a precursor is first reported to synthesize rod structures with abundant mesopores and defects (PTA-700). These features can provide more active sites and space for lithium and sodium ions storage, which is conducive to lithium and sodium ions transfer. Excellent electrochemical performance is observed in LIBs (535 mAh/g after 100 cycles at 0.1 A/g) and SIBs (114.0 mAh/g after 3000 cycles at 1 A/g). Kinetics analysis and density functional theory (DFT) calculations were carried out to further analyze the superior lithium and sodium ions storage performance of PTA-700. More importantly, PTA-700 solves many problems faced by traditional biomass-derived carbons in commercialization. Our work suggests an effective way to develop high-performance biomass-derived carbon anode materials for LIBs and SIBs.

Morphology-Controlled Synthesis of V1.11S2 for Electrocatalytic Hydrogen Evolution Reaction in Acid Media.

High-performance low-cost catalysts are in high demand for the hydrogen evolution reaction (HER). In the present study, we reported that V1.11S2 materials with flower-like, flake-like, and porous morphologies were successfully synthesized by hydrothermal synthesis and subsequent calcination. The effects of morphology on hydrogen evolution performance were studied. Results show that flower-like V1.11S2 exhibits the best electrocatalytic activity for HER, achieving both high activity and preferable stability in 0.5 M H2SO4 solution. The main reason can be ascribed to the abundance of catalytically active sites and low charge transfer resistance.

Nitrogen-Doped Hollow Carbon Spheres Based on Schiff Base Reaction as an Anode Material for High-Performance Lithium and Sodium Ion Batteries.

Nitrogen-doped carbon has great potential in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), considering N-doping can not only improve the surface wettability of carbon materials, but also accelerate charge transfer by generating additional defects. However, designing carbon materials with a high nitrogen content and uniform distribution using conventional doping methods remains a challenge. In this study, a hollow carbon sphere with an ultrahigh nitrogen content of 9.58 wt % was successfully fabricated by rationally designing Schiff base chemistry (PTA-NHCS-700). Stable hierarchical pore structures, moderate defects, and large specific surface areas were formed during the carbonization process. Excellent electrochemical performance was observed in LIBs (204.2 mAh g-1 after 7000 cycles at 5 A g-1 ) and SIBs (154.2 mAh g-1 after 10000 cycles at 5 A g-1 ). This study not only promotes the development of efficient carbon anode materials for LIBs and SIBs, but also provides a novel idea for the doping of heteroatoms with special chemical structures.

High-Efficiency Ammonia Electrosynthesis on Anatase TiO2-x Nanobelt Arrays with Oxygen Vacancies by Selective Reduction of Nitrite.

Electrocatalytic reduction of nitrite to NH3 provides a new route for the treatment of nitrite in wastewater, as well as an attractive alternative to NH3 synthesis. Here, we report that an oxygen vacancy-rich TiO2-x nanoarray with different crystal structures self-supported on the Ti plate can be prepared by hydrothermal synthesis and by subsequently annealing it in an Ar/H2 atmosphere. Anatase TiO2-x (A-TiO2-x) can be a superb catalyst for the efficient conversion of NO2- to NH3; a high NH3 yield of 12,230.1 ± 406.9 µg h-1 cm-2 along with a Faradaic efficiency of 91.1 ± 5.5% can be achieved in a 0.1 M NaOH solution containing 0.1 M NaNO2 at -0.8 V, which also exhibits preferable durability with almost no decay of catalytic performances after cycling tests and long-term electrolysis. Furthermore, a Zn-NO2- battery with such A-TiO2-x as a cathode delivers a power density of 2.38 mW cm-2 as well as a NH3 yield of 885 µg h-1 cm-2.

Construction of V1.11S2 flower spheres for efficient aqueous Zn-ion batteries.

Aqueous zinc-ion batteries (AZIBs) have become a focus due to their high safety, low cost, and environmental protection. Vanadium-based materials are commonly used as cathodes in AZIBs. As technology improves, more types of vanadium-based materials are successfully synthesized and applied. To find more suitable cathode materials, we first investigated the utility of V1.11S2 spheres for AZIB cathodes, which were synthesized by a facile solvothermal method. Benefiting from the excellent morphology and stable chemical system, the electrode exhibits continuous capacity growth during the cycling process and maintains stability over a long period of time. In addition, it has an outstanding rate capability. Specifically, the capacity reaches 224.8 mAh g-1 at 0.1 A g-1 and increases from 39.1 to 51.4 mAh g-1 at 2 A g-1 after 2000 cycles. Such characteristics can be attributed to the continuous and slow activation of the electrode and the growth of the specific surface area due to the scattered nanosheets, which allows the electrolyte to fully penetrate into the material and expose more active sites. Meanwhile, the increased V1.11S2 layer spacing due to the embedding of water molecules can provide a wide channel for ion transport. This work may provide new ideas for the synthesis and development of vanadium-based materials used in AZIBs.

Boosting electrochemical nitrite-ammonia conversion properties by a Cu foam@Cu2O catalyst.

Electrocatalytic reduction of nitrite (NO2-) to ammonia (NH3) can simultaneously achieve wastewater treatment and ammonia production, but it needs efficient catalysts. Herein, Cu2O particles self-supported on Cu foam with enriched oxygen vacancies are developed to enable selective NO2- reduction to NH3, exhibiting a maximum NH3 yield rate of 7510.73 µg h-1 cm-2 and high faradaic efficiency of 94.21% at -0.6 V in 0.1 M PBS containing 0.1 M NaNO2. Density functional theory calculations reveal the vital role of oxygen vacancies during the nitrite reduction process, as well as the reaction mechanisms and the potential limiting step involved. This work provides a new avenue to the rational design of Cu-based catalysts for NH3 electrosynthesis.

Ultra-wideband and wide-angle perfect solar energy absorber based on Ti nanorings surface plasmon resonance.

Solar energy absorption is a very important field in photonics. The successful development of an efficient, wide-band solar absorber is an extremely powerful driver in this field. We propose an ultra-wideband (UWB) solar energy absorber composed of a Ti ring and SiO2-Si3N4-Ti thin films. In the range of 300-4000 nm, the wide band has an absorption efficiency of more than 90% and can reach 3683 nm, and it has four absorption peaks with a high absorptivity. Moreover, the weighted average absorption efficiency of the solar absorber under AM 1.5 is maintained above 97.03%, which indicates it has great potential for use in the field of solar energy absorption. Moreover, we proved that the polarization is insensitive by analyzing the absorption characteristics at arbitrary polarization angles. For both the transverse electric (TE) and transverse magnetic (TM) modes, the UWB absorption is maintained at more than 90% in the wide incidence angle range of 60°. The UWB solar energy absorber has great potential for use in a variety of applications, such as converting solar light and heat into electricity for public use and reducing the side effects of coal-fired power generation. It can also be used in information detection and infrared thermal imaging owing to its UWB characteristics.

Phase-Segregated SrCo0.8Fe0.5-xO3-δ/FexOy Heterostructured Catalyst Promotes Alkaline Oxygen Evolution Reaction.

Perovskite oxide is a promising alternative to noble metal electrocatalysts for the oxygen evolution reaction (OER). However, as one of the most active oxide catalysts, cubic SrCoO3 presents poor OER performance relative to the theoretically predicted activity. Appropriate introduction of a guest component in the lattice and surface could largely promote the OER activity. Herein, we present a thermal-induced phase-segregation strategy to synthesize a heterostructured SrCo0.8Fe0.5-xO3-δ/FexOy (SC8F5) catalyst for OER. This novel perovskite/Fe3O4 heterostructure allows us to enhance the electrical conductivity ability, increase the Co oxidation state, and activate the surface oxygen to active oxygen species (O22-/O-) for efficient OER. In contrast to the poor stability of SrCo0.8Fe0.2O3-δ, we found that the SC8F5 heterostructure with segregated Fe3O4 on the surface can mitigate surface reconstruction and stabilize the catalyst structure, thereby increasing catalytic stability.

Broadband polarization-insensitive and wide-angle solar energy absorber based on tungsten ring-disc array.

Nowadays, solar energy is considered one of the most clean energy sources. In addition, the data from the literature tell us that its main radiation bandwidth is approximately 295-2500 nm. In this work, we proposed a novel kind of broadband solar energy absorber based on tungsten (W) to achieve broadband absorption of solar energy. A four-layer ring-disk structure (SiO2-SiO2-W) is employed in our design. A finite-difference time-domain (FDTD) simulation was used to ascertain the absorption performance of the absorber. The results demonstrate that a broadband solar energy absorption was realized, the bandwidth is of 1530 nm with an absorption efficiency of more than 90%, and an absorption efficiency of 97% was achieved in this region. The absorption spectra can be tuned through changing the structural and geometric parameters. Moreover, the absorber has excellent polarization independence and can be used under incident angles from 0° to 60°. The proposed solar energy absorber is simple to fabricate, and can be used for photothermal conversion, solar energy harvesting and utilization.

CdS@MoS2 Hetero-structured Nanocomposites Are Highly Effective Photo-Catalysts for Organic Dye Degradation.

CdS@MoS2 hetero-structured nanocomposites (HSNPs) were successfully synthesized via a hydrothermal approach. The morphology and crystal structure of these composites as well as their ability to act as photocatalysts for the degradation of methylene blue were investigated using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and UV-vis absorption spectroscopy. The developed CdS@MoS2 nanocomposites exhibited an 80% degradation rate with 30 min of visible light irradiation. To characterize the basis of the photocatalytic properties of these materials, the transient photocurrent densities were determined for the CdS@MoS2 HSNPs and pure dendritic CdS nanotrees. The results suggest that the photocatalytic activity may reflect electron transfer between the conduction band maximum of CdS and MoS2. Additionally, the improved visible light absorption, decreased electron-hole pair recombination, and enhanced surface area for more effective dye absorption likely contribute to improved photocatalytic performance.

Tunable Broadband Solar Energy Absorber Based on Monolayer Transition Metal Dichalcogenides Materials Using Au Nanocubes.

In order to significantly enhance the absorption capability of solar energy absorbers in the visible wavelength region, a novel monolayer molybdenum disulfide (MoS2)-based nanostructure was proposed. Local surface plasmon resonances (LSPRs) supported by Au nanocubes (NCs) can improve the absorption of monolayer MoS2. A theoretical simulation by a finite-difference time-domain method (FDTD) shows that the absorptions of proposed MoS2-based absorbers are above 94.0% and 99.7% at the resonant wavelengths of 422 and 545 nm, respectively. In addition, the optical properties of the proposed nanostructure can be tuned by the geometric parameters of the periodic Au nanocubes array, distributed Bragg mirror (DBR) and polarization angle of the incident light, which are of great pragmatic significance for improving the absorption efficiency and selectivity of monolayer MoS2. The absorber is also able to withstand a wide range of incident angles, showing polarization-independence. Similar design ideas can also be implemented to other transition-metal dichalcogenides (TMDCs) to strengthen the interaction between light and MoS2. This nanostructure is relatively simple to implement and has a potentially important application value in the development of high-efficiency solar energy absorbers and other optoelectronic devices.

Biomass-derived carbon from Ganoderma lucidum spore as a promising anode material for rapid potassium-ion storage.

The design and preparation of powerful anode materials are key to developing potassium-ion batteries. A biomass-based potassium anode material with a distinct hollow-cage structure was prepared by one-step carbonization. The target carbon exhibited a specific surface area of 104.4 m2 g-1 and mesopores/macropores distributed materials. When used as the negative electrode of a potassium-ion battery, the cage-like porous carbon (CPC) showed a reversible capacity of 407 mAh g-1 after 50 cycles at 50 mA g-1 current density. After 100 cycles, at a current density of 200 mA g-1, the reversible capacity was 163.8 mAh g-1. It still exhibits an extremely long cycle stability at high current densities (discharge capacity of 124.6 mAh g-1 after 700 cycles at a current density of 1 A g-1). The excellent performance is attributed to the stable cage-like carbon scaffold and uniform continuous distribution of mesopores/macropores to improve ion diffusion kinetics and electronic conductivity. These results indicate that a properly designed CPC can effectively increase the capacity and cycle stability of a potassium-ion battery.

Fabrication of ZnO@MoS2 Nanocomposite Heterojunction Arrays and Their Photoelectric Properties.

In this paper, ZnO@MoS2 core-shell heterojunction arrays were successfully prepared by the two-step hydrothermal method, and the growth mechanism was systematically studied. We found that the growth process of molybdenum disulfide (MoS2) was sensitively dependent on the reaction temperature and time. Through an X-ray diffractometry (XRD) component test, we determined that we prepared a 2H phase MoS2 with a direct bandgap semiconductor of 1.2 eV. Then, the photoelectric properties of the samples were studied on the electrochemical workstation. The results show that the ZnO@MoS2 heterojunction acts as a photoanode, and the photocurrent reaches 2.566 mA under the conditions of 1000 W/m2 sunshine and 0.6 V bias. The i-t curve also illustrates the perfect cycle stability. Under the condition of illumination and external bias, the electrons flow to the conduction band of MoS2 and flow out through the external electrode of MoS2. The holes migrate from the MoS2 to the zinc oxide (ZnO) valence band. It is transferred to the external circuit through the glass with fluorine-doped tin oxide (FTO) together with the holes on the ZnO valence band. The ZnO@MoS2 nanocomposite heterostructure provides a reference for the development of ultra-high-speed photoelectric switching devices, photodetector(PD) devices, and photoelectrocatalytic technologies.

A Tunable Triple-Band Near-Infrared Metamaterial Absorber Based on Au Nano-Cuboids Array.

In this article, we present a design for a triple-band tunable metamaterial absorber with an Au nano-cuboids array, and undertake numerical research about its optical properties and local electromagnetic field enhancement. The proposed structure is investigated by the finite-difference time domain (FDTD) method, and we find that it has triple-band tunable perfect absorption peaks in the near infrared band (1000-2500 nm). We investigate some of structure parameters that influence the fields of surface plasmons (SP) resonances of the nano array structure. By adjusting the relevant structural parameters, we can accomplish the regulation of the surface plasmons resonance (SPR) peaks. In addition, the triple-band resonant wavelength of the absorber has good operational angle-polarization-tolerance. We believe that the excellent properties of our designed absorber have promising applications in plasma-enhanced photovoltaic, optical absorption switching and infrared modulator optical communication.