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Cobalt hydroxide is a promising electrode material for supercapacitors due to the high capacitance and long cyclability. However, the energy storage/conversion mechanism of cobalt hydroxide is still vague at the atomic level. Here we shed light on how cobalt hydroxide functions as a supercapacitor electrode at operando conditions. We find that the high specific capacitance and long cycling life of cobalt hydroxide involve a complete modification of the electrode morphology, which is usually believed to be unfavourable but in fact has little influence on the performance. The conversion during the charge/discharge process is free of any massive structural evolution, but with some tiny shuffling or adjustments of atom/ion species. The results not only unravel that the potential of supercapacitors could heavily rely on the underlying structural similarities of switching phases but also pave the way for future material design for supercapacitors, batteries and hybrid devices.

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The rate capability of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NMC) electrode is studied in this paper at the particle scale. Experimental results obtained on thin electrodes show that NMC is an extremely high-rate material capable of charge and discharge at rates exceeding 100C. The high capacity retention has not been previously reported in the literature. Even higher rate capability was seen on charge. The transport properties of the material were explored by combining experiments on thin electrodes with a continuum model of a single spherical particle. The use of thin electrodes minimized porous electrode effects and allowed the assumption of a uniform current distribution in the electrode. A qualitative estimate of the lithium diffusion coefficient in the NMC particle was obtained by comparing the experimental and simulated potentials during open-circuit relaxation at various states of charge. The fitting results show that the lithium diffusion coefficient increases with increasing state of charge. The value ranges from 10 −16 m 2 /s when completely discharged to 10 −14 m 2 /s when completely charged, suggesting that the use of a varying diffusion coefficient is necessary for studying the transport processes in this material and for further application to the macroscopic porous electrode models.

due to their different redox behaviors and/or diverse solubility product constants of these metal ions with hydroxide ions. Herein, we report a stepwise electrodeposition strategy to make an ultrathin NiFe film, whose catalytic activity for water oxidation is significantly improved as compared to the NiFe film formed by a typical cathodic electrolysis method. By using the stepwise strategy, that is first deposition of Ni-based film via cathodic electrolysis followed by the integration of Fe species via anodic CV (Figure 1), the amounts of Ni/Fe-based materials loaded on electrodes can be controlled. In addition, the interconnected reticular film structure resulted from stepwise deposition is favorable to electrocatalytic water oxidation by assisting both mass and charge transportation. This work should therefore be very valuable to film preparation that is interesting in electrocatalysis and other electrochemical studies.Typically, a layer of Ni-based film was first deposited on an electrode by cathodic electrolysis of an Ni(NO 3 ) 2 aqueous solution at an applied potential of −0.80 V versus normal hydrogen electrode (NHE) for 300 s. The electrode was then rinsed and immersed in a freshly prepared FeSO 4 acetate buffer (0.1 m, pH 7.0) under argon for CV incorporation of Fe into the previously formed Ni-based film. The CV deposition was conducted in one cycle of 0.20-1.35 V versus NHE. It is worth noting that prior to the dissolution of FeSO 4 , the acetate buffer is vigorously bubbled with argon for at least 30 min to remove the dissolved O 2 in the solution. Argon protection is essential to prevent the oxidation of Fe II to Fe III by O 2 , a step aimed at well-controlled Fe deposition. [21,22] This NiFe film from stepwise electrodeposition is denoted hereafter as NiFe-SW. The film evolution is illustrated in Figure 1 showing the optical images of the film on indium tin oxide (ITO) electrodes and scanning electron microscopy (SEM) images of the film on glassy carbon (GC) electrodes. The transparent nature of this ultrathin film permits its potential uses in photoactive devices. [21,31,32] The morphologies of electrodeposited films were analyzed by SEM and transmission electron microscopy (TEM). As shown in Figure 2A, Ni-based film from cathodic electrolysis was composed of isolated nanoplates with legible boundaries. Such isolated domains have been commonly observed for films that are electrodeposited using the electrolysis method. [18,23,26] After CV incorporation of Fe into the aforementioned Ni-based film, the resulting NiFe-SW film consisted of uniformly interconnected nanoribbons with porous structures (Figure 2B-D). TEM image of Ni-based film showed nanoplates with a layered morphology and edge steps, which was consistent with typical metal hydroxide structures ( Figure 2E). [45] On the contrary, NiFe-SW film evolved into curly and contorted nanosheets Increasing energy demands and environmental issues related to the use of fossil fuels have forced people to exploit sustainable and carbon-free energy resour...

We firstly propose the application of CNTs as novel catalysts and molecular oxygen as the oxidant for the oxidative desulfurization (ODS) of a model fuel containing benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at atmospheric pressure and low temperature.Results showed that when three CNTs including CNT-SZ, CNT-TS, and CNT-CD were separately used as catalysts with molecular oxygen as the oxidant, the conversion of DBT to its corresponding sulfone reached 100% at 150 °C separately within 40, 120 and 180 min. The CNT-SZ exhibited a superior catalytic activity even at a high fuel-to-catalyst ratio of 7.5 kg fuel per g catalyst. The oxidation reactivity of these benzothiophenic compounds followed the order: 4,6-DMDBT > DBT > BT. The deactivated CNT can be effectively regenerated by heat treatment under an argon atmosphere at 900 °C. Raman spectroscopy analysis revealed that the graphitization degree of the CNT played a decisive role in its catalytic activity for DBT oxidation. The CNT with the higher degree of graphitization had higher catalytic activity for DBT oxidation since its higher electric conductivity benefited the transfer of electrons involved in the oxidation-reduction reaction.

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