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A Co-metal–organic-framework (MOF) crystal has been hydrothermally synthesized. Then the corresponding Co/nitrogen-doped porous carbon (Co/NPC) composite is fabricated by direct pyrolyzation of MOF without any precursor additive. The results reveal that the MOF-derived Co/NPC exhibits a porous structure with a surface area of 412 m2 g−1 and a narrow pore size distribution (from 1.8 to 4.9 nm). The doped N mainly occurs in pyridine N and graphitic N types with total content as 4.11 at.%, which is originated from the N-based ligands in MOF. As an efficient oxygen reduction reaction (ORR) catalyst, Co/NPC shows a more positive onset potential (0.91 V vs. RHE) with a diffusion-limited current density of 5.46 mA cm−2 at 0.3 V (vs. RHE). The rotating disk electrode and rotating ring-disk electrode results suggest that the Co/NPC catalyst experiences a nearly 4e pathway with a stronger methanol tolerance and better durability than commercial Pt/C catalyst in 0.1 M KOH. The excellent ORR catalytic activity of Co/NPC can be attributed to the N-doped porous carbon structure with incorporated metallic Co active species. This work affords a new strategy for preparation of non-noble metal ORR catalysts employing MOF as a precursor.

This work describes the synthesis of a nanocomposite consisting of Ag2O, silver nanoparticles and N,S-doped carbon quantum dots (Ag2O/Ag@NS-CQD). The NS-CQD were prepared by hydrothermal treatment of p-aminobenzenesulfonic acid. They act as both the reducing and stabilizing agent for synthesis of Ag2O/Ag@NS-CQD. The composite was characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The glassy carbon electrode (GCE) was modified by coating it with Ag2O/Ag@NS-CQD. It exhibits excellent amperometric response to catechol, typically at a low working potential of around 0.25 V. Under the best experimental conditions, the sensor has a wide linear response (0.2 to 180 μM) and a low detection limit (13 nM; at S/N = 3). The method was applied to analysis of spiked water samples and gave satisfactory results.