Metal−organic frameworks (MOFs) can act as precursors or templates to a myriad of nanostructured materials that are difficult to prepare. In this study, Co-MOF nanorods (NRs) were prepared at room temperature followed by a calcination and hydrothermal sulfurization strategy to transform the MOF into CoS NRs on carbon cloth (CoS/CC). Intriguingly, the resultant 3D sulfide NRs can serve as scaffolds to electrodeposit layered double hydroxides (LDHs) on the surfaces. Through combining the advantages of structure and composition, the as-fabricated CoS@CoNi-LDH/CC exhibits remarkable electrocatalytic activity for the hydrogen evolution reaction (HER). An overpotential of 124 mV is needed to reach a current density of 10 mA cm −2 with a Tafel slope of only 89 mV dec −1 , which is superior to that of pure CoS/CC (141 mV along with 103 mV dec −1 ) and other reported cobaltbased catalysts. Notably, after the chronopotentiometry test for 50 h, the overpotential of CoS@CoNi-LDH/CC increased by 17 mV only.

Molybdenum disulfide has been one of the most studied hydrogen evolution catalyst materials in recent years, but its disadvantages, such as poor conductivity, hinder its further development. Here, we employ the common hydrothermal method, followed by an additional solvothermal method to construct an uncommon molybdenum disulfide with two crystal forms of 1T and 2H to improve catalytic properties. The low overpotential (180 mV) and small Tafel slope (88 mV/dec) all indicated that molybdenum disulfide had favorable catalytic performance for hydrogen evolution. Further conjunctions revealed that the improvement of performance was probably related to the structural changes brought about by the 1T phase and the resulting sulfur vacancies, which could be used as a reference for the further application of MoS2.

The development of cost-effective electrocatalysts for both hydrogen and oxygen evolution reactions (HER and OER) in alkaline media is crucial in renewable energy conversion technologies. Metal–organic frameworks (MOFs) can act as precursors to the design and construct of varied nanostructured materials which may be difficult to produce in other ways. Herein, we put forward a serial ion-exchange reaction and selenation strategy to prepare novel yolk–shelled Ni–Co–Se dodecahedral nanocages on carbon fiber paper (Y–S Ni–Co-Se/CFP). ZIF-67@LDH/CFP was first synthesized by a simple ion-exchange reaction, followed by a hydrothermal selenation process to form Y–S Ni–Co-Se/CFP. Moreover, the composition of the as-prepared yolk–shelled Ni–Co–Se nanocages was a mixture of Co0.85Se and Ni0.85Se (Co/Ni atomic ratio of about 2.42). Due to their structural and compositional merits, the as-prepared Y–S Ni–Co-Se/CFP exhibited remarkable electrocatalytic activity and long-term stability (over 80% current retention for at least 18 h) for both HER and OER. For HER, it required an overpotential of 250 mV to attain a current density of 10 mA cm–2, which was 162 mV less than that of the Y–S Co0.85Se/CFP counterpart. The catalyst also efficiently catalyzed OER with a current density of 10 mA cm–2 at an overpotential of 300 mV, which was lower than those of other reported Co-based catalysts.

The recent use of cryoprotectant replacement method for solving the easy drying problem of hydrogels has attracted increasing research interest. However, the conductivity decrease of organohydrogels due to the induced insulating solvent limited their electronic applications. Herein, we introduce the Hofmeister effect and electrostatic interaction to generate hydrogen and sodium bonds in the hydrogel. Combined with its double network, an effective charge channel that will not be affected by the solvent replacement, is therefore built. The developed organohydrogel-based single-electrode triboelectric nanogenerator (OHS-TENG) shows low conductivity decrease (one order) and high output (1.02−1.81 W/m 2 ), which is much better than reported OHS-TENGs (2− 3 orders, 41.2−710 mW/m 2 ). Moreover, replacing water with glycerol in the hydrogel enables the device to exhibit excellent long-term stability (four months) and temperature tolerance (−50−100 °C). The presented strategy and mechanism can be extended to common organohydrogel systems aiming at high performance in electronic applications.

Herein, we report an eco-friendly and simple fluorescent nitrogen-doped carbon quantum dot (N-CQD) biosensor which was synthesized via a hydrothermal method using erhanediamine (EDA) and citric acid (CA) as precursors. The surface functionalization of N-CQDs exhibited a bright blue emission under the excitation wavelength of 350 nm. The obtained N-CQDs were characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and transmission electron microscopy. It was found that the surface of the CQDs was successfully functionalized. After that, as-prepared N-CQDs were further applied in Fe(III) detection. Spectroscopic data indicated that fluorescent carbon-based nanomaterials displayed a sensitive response to Fe in the range of 0.5-1000 μM as a fluorescence sensor in real environmental samples. Furthermore, the results also showed that a novel N-CQD nanomaterial could be employed as an ideal fluorescent Fe(III) probe.