Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15 N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1 H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2 O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2 O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.

Unveiling the Activity Origin of a Copper-based Electrocatalyst for Selective Nitrate Reduction to Ammonia.

Electrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 μg h−1 mgcat.−1 (0.46 mmol h−1 cm−2). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N2 due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites. Developing green and delocalized routes for ammonia synthesis is highly important but still very challenging. Here the authors report an efficient ammonia synthesis process via nitrate reduction to ammonia on Fe single atom catalyst.

/pdf/electrochemical-ammonia-synthesis-via-nitrate-reduction-on-3fjroehwqt.pdf

Electrochemical ammonia synthesis via nitrate reduction on Fe single atom catalyst.

Nitrate enrichment, which is mainly caused by the over-utilization of fertilisers and industrial sewage discharge, is a major global engineering challenge because of its negative influence on the environment and human health. To solve this serious problem, many technologies, such as the activated sludge method, reverse osmosis, ion exchange, adsorption, and electrodialysis, have been developed to reduce the nitrate levels in water bodies. However, the applications of these traditional techniques are limited by several drawbacks, such as a long sludge retention time, slow kinetics, and undesirable by-products. From an environmental perspective, the most promising nitrate reduction technology is enabled to convert nitrate into benign N2, and features low cost, high efficiency, and environmental friendliness. Recently, electrocatalytic nitrate reduction has been proven by satisfactory research achievements to be one of the most promising methods among these technologies. This review provides a comprehensive account of nitrate reduction using electrocatalysis methods. The fundamentals of electrocatalytic nitrate reduction, including the reaction mechanisms, reactor design principles, product detection methods, and performance evaluation methods, have been systematically summarised. A detailed introduction to electrocatalytic nitrate reduction on transition metals, especially noble metals and alloys, Cu-based electrocatalysts, and Fe-based electrocatalysts is provided, as they are essential for the accurate reporting of experimental results. The current challenges and potential opportunities in this field, including the innovation of material design systems, value-added product yields, and challenges for products beyond N2 and large-scale sewage treatment, are highlighted.

Electrocatalytic reduction of nitrate - a step towards a sustainable nitrogen cycle.

. Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property, heat-insulating ability and compression resistance are highly attractive in practical applications. Meeting the aforesaid requirements simultaneously is a formidable challenge. Herein, ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process, forming porous network architecture. With the heating platform temperature of 70 °C, the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend. The color of the sample surface in thermal infrared images is similar to that of the surroundings. With the maximum compressive stress of 2.435 kPa, the carbon aerogels can provide favorable endurance. The shaddock peel-based carbon aerogels possess the minimum reflection loss value (RLmin) of − 29.50 dB in X band. Meanwhile, the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm. With the detection theta of 0°, the maximum radar cross-sectional (RCS) reduction values of 16.28 dB m2 can be achieved. Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature. This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.

/pdf/environmentally-friendly-and-multifunctional-shaddock-peel-1tahho30hs.pdf

Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption.

The electrochemical nitrate reduction reaction (NITRR) provides a promising solution for restoring the imbalance in the global nitrogen cycle while enabling a sustainable and decentralized route to source ammonia. Here, we demonstrate a novel electrocatalyst for NITRR consisting of Rh clusters and single-atoms dispersed onto Cu nanowires (NWs), which delivers a partial current density of 162 mA cm-2 for NH3 production and a Faradaic efficiency (FE) of 93% at -0.2 V vs. RHE. The highest ammonia yield rate reached a record value of 1.27 mmol h-1 cm-2. Detailed investigations by electron spin resonance, in-situ infrared spectroscopy, differential electrochemical mass spectrometry and density functional theory modeling suggest that the high activity originates from the synergistic catalytic cooperation between Rh and Cu sites, whereby adsorbed hydrogen on Rh sites transfer to vicinal *NO intermediate species adsorbed on Cu promoting the hydrogenation and ammonia formation.

/pdf/efficient-electrochemical-nitrate-reduction-to-ammonia-with-3v3uzwy9.pdf

Efficient Electrochemical Nitrate Reduction to Ammonia with Copper Supported Rhodium Cluster and Single-Atom Catalysts.

Electrocatalytic denitrification is considered as the most promising technology to transform nitrates to nitrogen gas in sewage so far. Although noble metal-based catalysts as a cathode material ha...

Tailoring the Assembly of Iron Nanoparticles in Carbon Microspheres toward High-Performance Electrocatalytic Denitrification.

Achieving effective broadband microwave absorption with Fe3O4@C supraparticles

Structurally nanocrystalline electrically monocrystalline Sb2Te3 with high thermoelectric performance

The invention relates to Fe3O4/C and Fe/C based on carbon cloth as well as preparation and application. The Fe3O4/C based on the carbon cloth is obtained by taking Fe3O4 colloidal nanocrystalline as aconstruction unit and taking the carbon cloth as a carrier through self-assembly, carbonization and reduction, the method is simple and convenient to operate, and conditions are easy to control.

Fe3O4/C and Fe/C based on carbon cloth as well as preparation and application

The invention relates to a solid super-structure microsphere (Fe3O4@C) wave-absorbing material and a preparation method and application thereof. The method comprises the following steps: preparing a Fe3O4 nanoparticle precursor, preparing Fe3O4 nanoparticles, preparing a microemulsion system, and preparing the Fe3O4@C superstructure microsphere wave-absorbing material. The method is simple, convenient, easy to operate, low in carbonization temperature and low in energy consumption. The prepared Fe3O4@C superstructure microsphere wave-absorbing material has good wave-absorbing efficiency and awide effective absorption frequency band, and can realize effective absorption of full coverage of an X wave band.

Solid Fe3O4@C superstructure microsphere wave-absorbing material and preparation method and application thereof

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