Among numerous active electrode materials, nickel hydroxide is a promising electrode in electrochemical capacitors. Nickel hydroxide research has thus far focused on the crystalline rather than the amorphous phase, despite the impressive electrochemical properties of the latter, which includes an improved electrochemical efficiency due to disorder. Here we demonstrate high-performance electrochemical supercapacitors prepared from amorphous nickel hydroxide nanospheres synthesized via simple, green electrochemistry. The amorphous nickel hydroxide electrode exhibits high capacitance (2,188 F g−1), and the asymmetric pseudocapacitors of the amorphous nickel hydroxide exhibit high capacitance (153 F g−1), high energy density (35.7 W h kg−1 at a power density of 490 W kg−1) and super-long cycle life (97% and 81% charge retentions after 5,000 and 10,000 cycles, respectively). The integrated electrochemical performance of the amorphous nickel hydroxide is commensurate with crystalline materials in supercapacitors. These findings promote the application of amorphous nanostructures as advanced electrochemical pseudocapacitor materials.

Cobalt hydroxide (Co(OH)2) has received extensive attention for its exceptional splendid electrical properties as a promising supercapacitor electrode material. Co(OH)2 study so far prefers to crystal instead of amorphous, in spite of amorphous impressive electrochemical properties including the ability to improve the electrochemical efficiency based on the disorder structure. The amorphous Co(OH)2 nanostructures with excellent electrochemical behaviors were successfully synthesized by a simple and green electrochemistry. Our as-prepared Co(OH)2 electrode exhibited ultrahigh capacitance of 1094 F g(-1) and super long cycle life of 95% retention over 8000 cycle numbers at a nominal 100 mV s(-1) scan rate. The united pseudo-capacitive performances of the amorphous Co(OH)2 nanostructures in electrochemical capacitors are totally comparable to those of the crystalline Co(OH)2 nanomaterials. These findings actually open a door to applications of amorphous nanomaterials in the field of energy storage as superior electrochemical pseudocapacitors materials.

We have developed simple and green electrochemistry to synthesize Ag nanostructures with high purity, good crystallinity and smooth surface for applications as super-SERS (surface-enhanced Raman scattering), SERS-active substrates and with highly effective antimicrobial activities. This synthesis takes place in a clean and slow reaction environment without any chemical additives, which ensures an ultrahigh active surface of the as-synthesized Ag nanostructures owing to their purity, good crystallinity and smooth morphology. Using this method, we synthesized nearly perfect Ag nanodendrites (NDs), which exhibit super-SERS sensitivity when they are used to detect the SERS spectra of rhodamine 6G at concentrations as low as 5 × 10(-16) M, and have an ultrahigh electromagnetic (EM) enhancement factor of the order of 10(13), breaking through the theoretical limit of EM enhancement. Meanwhile, the as-synthesized Ag NDs possess highly effective antimicrobial activities for Escherichia coli, Candida albicans and Staphylococcus aureus, which are over 10 times that of silver nanoparticles. Additionally, the basic physics and chemistry involved in the fabrication of Ag nanostructures are pursued. These investigations show that silver nanostructures with highly active surfaces can make the most of Ag nanostructures functioning as super-SERS-active substrates and multiple antibiotics.

Good conductivity is conventionally considered as a typical reference standard in terms of selecting water electrolysis catalysts. Cobalt hydroxide (Co(OH)2) has received extensive attention for its exceptional properties as a promising electrocatalysis catalyst. However, research on Co(OH)2 so far prefers to its crystal phase instead of amorphous phase because the former generally exhibits better conductivity. Here, we have demonstrated that the amorphous Co(OH)2 electrocatalyst synthesized via a simple, facile, green, and low-cost electrochemistry technique possesses high activity and long-term cycle stability in the oxygen evolution reaction (OER). The as-synthesized Co(OH)2 electrode was found to be a promising electrocatalyst for mediating OER in alkaline media, as evidenced by the overpotential of 0.38 V at a current density of 10 mA cm−2 and a Tafel slope of 68 mV dec−1. The amorphous Co(OH)2 also presented outstanding durability and its stability was just as well as that of crystalline Co(OH)2. Generally, the integrated electrochemical performances of the amorphous Co(OH)2 in the OER process were much superior to that of the crystalline Co(OH)2 materials. We also established that the short-range order, i.e., nanophase, of amorphous Co(OH)2 creates a lot of active sites for OER which can greatly promote the electrocatalysis performance of amorphous catalysts. These findings showed that the conventional understanding of selecting electrocatalysts with conductivity as a typical reference standard seems out of date for developing new catalysts at the nanometer, which actually open a door to applications of amorphous nanomaterials as an advanced electrocatalyst in the field of water oxidation.

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