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Dynamic rheological measurements indicate that supra-molecules, polymers and carbogenic nanoparticles are generated successively during pyrolysis of citric acid based nanodots.

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Electrocatalytic reduction of nitrates (NO 3 RR) selectively generating ammonia (NH 3 ) opens up a new idea for treating nitrates in wastewater, which not only reduces nitrates but also obtains the valuable product ammonia. By first-principles calculations, we explore the activity and selectivity for NO 3 RR to NH 3 of TM/g-C 3 N 4 single-atom catalysts. Six TM/g-C 3 N 4 catalysts (TM = Ti, Os, Ru, Cr, Mn, and Pt) are selected by a four-step screening method. Ru/g-C 3 N 4 is the most promising of these six TM/g-C 3 N 4 catalysts because of its lowest energy barrier and extraordinary selectivity. The origin of the NO 3 RR activity of Ru/g-C 3 N 4 is explained from the viewpoint of NO 3 − adsorption. In addition, the hydrogen evolution reaction has also been implied to be uncompetitive for the poor adsorption on H atoms. This work provides a screening mechanism for finding new catalysts for NO 3 RR to NH 3 , promotes the development of NO 3 RR, and provides a stimulating impetus for further experimental exploration.

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In this work, few layer graphene quantum dots (GQDs) with a size of 3-5 nm are purposely treated with highly concentrated aqueous NaBH4 solutions to obtain the reduced graphene quantum dots (rGQDs). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy demonstrate that the number of carbonyl groups decreases but -OH related defects increase during chemical reduction. Green and weak emissions of original GQDs originate from carrier recombination in the disorder-induced localized state (mainly including carbonyl and carboxyl and epoxy groups). As the reduction degree increases, the photoluminescence (PL) quantum efficiency of GQDs increases dramatically from 2.6% to 10.1%. In the meantime, the PL peak position blue shifts rapidly, and full width at half maximum (FWHM) becomes narrower. Thus we can infer that graphenol topological defects (hydroxyl functionalized graphene) are gradually formed during reduction. Besides, graphenol defect related PL features a longer fluorescence lifetime, excitation wavelength dependence but less pH sensitivity.

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