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Spherical Ni2SnO4 nanoparticles were uniformly loaded on reduced graphene oxide (RGO) sheets via a hydrothermal process. The obtained nickel stannate–reduced graphene oxide (Ni2SnO4–RGO) composite was used as a catalyst for activating persulfate (PS). The heterostructure composed of Ni2SnO4 and RGO prevents both the agglomeration of Ni2SnO4 nanoparticles and the restacking of RGO sheets. The synergy between the two components affords enhanced Ni2SnO4–RGO catalytic activity. Using Ni2SnO4–RGO to activate PS can degrade bisphenol A (BPA) at a faster rate with less PS, in comparison with the most recently reported catalysts. BPA solution (50 mL, 0.10 mM) can be 100% degraded by PS (0.02 g) within 30 min at pH 8 using Ni2SnO4–RGO (0.02 g) as the catalyst. Moreover, the preparation of Ni2SnO4–RGO is simple, inexpensive and environment-friendly. The radical scavenging study indicates that sulfate radicals () and hydroxyl radicals (˙OH) are involved in the oxidation, in which plays a leading role. In addition, Ni2SnO4–RGO retains high catalytic activity after four consecutive cycles, exhibiting greatly enhanced stability in comparison with Ni2SnO4. Besides, the effect of different inorganic anions on the degradation was also explored. [ABSTRACT FROM AUTHOR]

Constructing a 3D hierarchical structure of electrode materials is a fast-developing technology to meet the increasing demand of high-rate electrochemical capacitors. Here, hierarchical CoNi2S4 nanofibers with pompom-like morphology are successfully synthesized via a two-step anion exchange reaction. The obtained CoNi2S4 nanofibers interweave densely with each other from inner core to external surface, constructing a stable 3D nanostructure. The pompom-like CoNi2S4 nanofibers have a high specific surface area of 169.7 m2 g−1 and a uniform nanopore size distribution in the range of 1–10 nm. Benefiting from these structural features, the pompom-like CoNi2S4 nanofibers provide more effective charge transport during electrochemical reactions compared with other 3D hierarchical structured CoNi2S4, such as flower-like nanosheets and urchin-like nanoneedles prepared by conventional methods. When evaluated as electrode materials in electrochemical tests, CoNi2S4 nanofibers with pompom-like hierarchical structure deliver a high specific capacitance of 2078.9 F g−1 at 0.5 A g−1 and an excellent rate capability of 844.4 F g−1 at 50 A g−1. The assembled CoNi2S4 nanofibers//activated carbon asymmetric electrochemical capacitor exhibits a good energy density of 48.2 W h kg−1 at a power density of 850 W kg−1, and a good cycling stability with 92.6% of its capacitance retained after 1000 cycles, suggesting that the pompom-like CoNi2S4 nanofibers can be applied as promising electrode materials for high-rate electrochemical capacitors. [ABSTRACT FROM AUTHOR]