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Ammonia is an indispensable commodity in the agricultural and pharmaceutical industries. Direct nitrate‐to‐ammonia electroreduction is a decentralized route yet challenged by competing side reactions. Most catalysts are metal‐based, and metal‐free catalysts with high nitrate‐to‐ammonia conversion activity are rarely reported. Herein, it is shown that amorphous graphene synthesized by laser induction and comprising strained and disordered pentagons, hexagons, and heptagons can electrocatalyze the eight‐electron reduction of NO3− to NH3 with a Faradaic efficiency of ≈100% and an ammonia production rate of 2859 µg cm−2 h−1 at −0.93 V versus reversible hydrogen electrode. X‐ray pair‐distribution function analysis and electron microscopy reveal the unique molecular features of amorphous graphene that facilitate NO3− reduction. In situ Fourier transform infrared spectroscopy and theoretical calculations establish the critical role of these features in stabilizing the reaction intermediates via structural relaxation. The enhanced catalytic activity enables the implementation of flow electrolysis for the on‐demand synthesis and release of ammonia with >70% selectivity, resulting in significantly increased yields and survival rates when applied to plant cultivation. The results of this study show significant promise for remediating nitrate‐polluted water and completing the NOx cycle.

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Magnetic Fe 3 O 4 @graphene-phenolic resin (FGR-PR) composites with negative permittivity were prepared by chemical coprecipitation and pressing method. Alternating current conductivity, permittivity, and permeability of the FGR-PR composites were investigated. An obvious percolation phenomenon was observed with the increase of FGR content from 84 to 91 vol%. Two types of negative permittivity attributed to the Lorentz and the Drude model, respectively, w e r e o b s e r v e d i n t h e c o m p o s i t e s . D u e t o t h e magnetocrystalline anisotropy and saturation magnetization, the real permeability enhanced from 1.17 to 4.1 with the increasing FGR content from 6 to 98 vol%. In addition, the frequency dispersion of permeability was attributed to the domain wall and the gyromagnetic spin resonance. The magnetic loss decreased firstly in the low frequency, attributing to the natural resonance, and then increased in the high frequency from the eddy current.

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The graphene/alumina (GR/Al2O3) composites with adjustable negative permittivity were prepared by spark plasma sintering method. The microstructures of the composites with different GR contents were investigated by field emission scanning electron microscopy. With increasing the GR content, the grain size of Al2O3 tended to decrease and the grain shape transformed from granulous to ellipsoidal. The radio frequency dielectric properties of the GR/Al2O3 composites including permittivity (ε′ and ε″), dielectric loss tangent (tan δ) and reactance (Z″) were investigated. The negative permittivity appeared when the GR content exceeded 15.38 wt %. The plasma oscillation of conduction electrons in the GR networks was considered to cause the negative permittivity. The maximum dielectric loss tangent for the GR/Al2O3 composites with the GR mass fraction of 15.38 and 18.46 wt % appeared near 40 and 70 MHz, respectively, corresponding to the transition of ε′ from negative to positive, which was produced by the LC resonance. The impedance of the GR/Al2O3 composites with the equivalent circuit models was also discussed.