Synthesis of FeOOH/Zn(OH)2/CoS Ferromagnetic Nanocomposites and the Enhanced Mechanism of Magnetic Field for Their Electrochemical Performances.

The FeOOH/Zn(OH)2/CoS (FZC) nanocomposites are synthesized and show the outstanding electrochemical properties in both supercapacitor and catalytic hydrogen production. The specific area capacitance reaches 17.04 F cm-2, which is more than ten times higher than that of FeOOH/Zn(OH)2 (FZ) substrate: 1.58 F cm-2). FZC nanocomposites also exhibit the excellent cycling stability with an initial capacity retention rate of 93.6% after 10 000 long-term cycles. The electrolytic cell (FZC//FZC) assembled with FZC as both anode and cathode in the UOR (urea oxidation reaction)|| HER (hydrogen evolution reaction) coupled system requires a cell voltage of only 1.453 V to drive a current density of 10 mA cm-2. Especially, the electrochemical performances of FZC nanocomposites are enhanced in magnetic field, and the mechanism is proposed based on Stern double layer model at electrode-electrolyte interface (EEI). More electrolyte ions reach the surface of FZC electrode material under Kelvin force, moreover, the warburg impedance of FZC nanocomposites decrease under magnetic field action, which results in the enhanced behaviors for both the energy storage and urea oxidation reaction .

The synthesis of CoS/MnCo2O4-MnO2 nanocomposites for supercapacitors and energy-saving H2 production.

In this study, CoS/MnCo2O4-MnO2 (CMM) nanocomposites were synthesized by hydrothermal and then electrochemical deposition. Their electrochemical properties were systematically investigated for supercapacitors and energy-saving H2 production. As an electrode material for supercapacitor, CMM demonstrates a specific capacitance of 2320F g-1 at 1 A/g, and maintains a specific capacitance of 1216F g-1 at 10 A/g. It also shows 72.8 % capacitance retention after 8000 cycles. The aqueous asymmetric supercapacitor exhibited high energy storage capacity (887.86F g-1 specific capacitance at a current density of 1 A/g), good rate performance and cycling stability. Besides, CMM shows outstanding urea oxidation reaction(UOR) and glycol oxidation reaction (MOR) performances for H2 production. Compared to oxygen evolution reaction (OER) (1.635 V) at 20 mA cm-2, the potentials were reduced by 213 mV for UOR and 233 mV for MOR, respectively. Therefore, this study shows the promising practical applications of CMM nanocomposites for energy storage and energy-saving H2 production.