Pectin as a novel natural kinetic hydrate inhibitor, expected to be eco-friendly and sufficiently biodegradable, was studied in this paper. The novel crystal growth inhibition (CGI) and standard induction time methods were used to evaluate its effect as hydrate inhibitor. It could successfully inhibit methane hydrate formation at subcooling temperature up to 12.5 °C and dramatically slowed the hydrate crystal growth. The dosage of pectin decreased by 66% and effective time extended 10 times than typical kinetic inhibitor. Besides, its maximum growth rate was no more than 2.0%/h, which was far less than 5.5%/h of growth rate for PVCap at the same dosage. The most prominent feature was that it totally inhibited methane hydrate crystal rapid growth when hydrate crystalline occurred. Moreover, in terms of typical natural inhibitors, the inhibition activity of pectin increased 10.0-fold in induction time and 2.5-fold in subcooling temperature. The extraordinary inhibition activity is closely related to its hydrogen bonding interaction with water molecules and the hydrophilic structure. Finally, the biodegradability and economical efficiency of pectin were also taken into consideration. The results showed the biodegradability improved 75.0% and the cost reduced by more than 73.3% compared to typical commercial kinetic inhibitors.

The universal linear scan voltammogram measurement on the rotating disk electrode (RDE) has been identified as a simple method to investigate the oxygen reduction activity of electrocatalysts. The steady‐state limiting current density Ilim indicates the maximum diffusion current density in the oxygen reduction reaction (ORR) during RDE measurement, which should be a fixed value in theory for a 4e ORR in a particular concentration solution and at a certain rotate speed. However, in experiments, Ilim is always variable and smaller than theoretical value even though with the same the catalyst, electrode, and rotator. So the impact of various experimental operating parameters on Ilim is highly necessary to be investigated. In this paper, factors, such as catalyst loading, O2 inlet condition, O2 flow rate, gas tightness, solution concentration, and purity, have been investigated for their effects on the Ilim of ORR on three typical catalysts (20 % commercial Pt/C, Iron/Nitrogen/Carbon‐catalyst and N‐doped carbon nanotubes). The results indicate that the catalyst loading and O2 inlet condition are the key factors influencing the Ilim of ORR. While, the O2 flow rate, gas tightness, solution concentration, and purity have little influence on the Ilim of ORR. The correct Ilim could be obtained under the optimized catalyst loading and the O2 inlet with an extended sand core tube.

Developing low cost, high-performance, and durable bifunctional catalysts for oxygen reduction and oxygen evolution reactions is critical for a commercial application of fuel cells and metal−air batteries. Nitrogen-doped carbon nanotubes encapsulated nickel nanoparticles are prepared through a simple pyrolysis procedure with melamine and nickel chloride hexahydrate as precursors. The catalyst is featured by nickel nanoparticles encapsulated inside nitrogen-doped carbon nanotubes, with abundant surface nitrogen doping. The optimized catalyst exhibits proximate oxygen reduction activity to platinum/carbon catalyst, comparable oxygen evolution activity to ruthenium dioxide catalyst, and better stability to noble metal catalysts in alkaline medium. The oxygen electrode activity parameter (the gap between the potential of oxygen evolution at 10 mA cm −2 and the half-wave potential of oxygen reduction) of the as-prepared catalyst is 0.754 V, which is among the state-ofthe-art bifunctional electrocatalysts reported to date. To explore the active sites, a series of catalysts with different bulk nickel and surface nitrogen contents are synthesized and served as the oxygen reduction and oxygen evolution reactions catalysts. The results reveal that the oxygen reduction activity of this catalyst arises from the doped nitrogen, while the oxygen evolution activity originates from the encapsulated nickel nanoparticles.

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Co-Doped MoS2/graphene hybrids with more exposed active sites and a Tafel slope of 44.3 mV dec−1 for HER were prepared.

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An SnCoS4/graphene composite with uniformly distributed SnCoS4 hybrid nanocrystals was prepared by a one-pot hydrothermal route and exhibits excellent electrochemical performance for reversible lithium storage.