In Situ Synthesis and Electrophoretic Deposition of NiO/Ni Core-Shell Nanoparticles and Its Application as Pseudocapacitor

Abstract

A simple, low cost and transferable colloidal processing method and the subsequent heat treatment has been optimized to prepare binder-free electrodes for their application in supercapacitors. NiO/Ni core-shell hybrid nanostructures have been synthetized by heterogeneous precipitation of metallic Ni nanospheres onto NiO nanoplatelets as seed surfaces. The electrophoretic deposition (EPD) has been used to shape the electroactive material onto 3D substrates such as Ni foams. The method has allowed us to control the growth and the homogeneity of the NiO/Ni coatings. The presence of metallic Nickel in the microstructure and the optimization of the thermal treatment have brought several improvements in the electrochemical response due to the connectivity of the final microstructure. The highest specific capacitance value has been obtained using a thermal treatment of 325 • C during 1 h in Argon. At this temperature, necks formed among ceramic-metallic nanoparticles preserve the structural integrity of the microstructure avoiding the employment of binders to enhance their connectivity. Thus, a compromise between porosity and connectivity should be established to improve electrochemical performance.

Electrophoretic deposition of RGO-NiO core-shell nanostructures driven by heterocoagulation method with high electrochemical performance

“…The synthesis was made by mixing 8 mmol of nickel nitrate hexahydrated (Ni(NO 3 ) 2 , 99.9% purity; Panreac, Spain), and 40 mmol of ammonia (NH 3 , 28%, Panreac, Spain) in a total volume of 80 ml of aqueous solution. This procedure was previously described more in detail elsewhere [10,31,35].…”

“…The development of hybrid capacitors may result in a superior performance since both storage energy phenomena (ionic double layer and redox reactions) take place at the same time [8,9]. Among all the transition metal oxides, NiO is consider a promising candidate in the manufacturing of supercapacitors due to their high theoretical specific capacitance (3750 F/g), chemical and thermal stability and low cost [10,11]. However, it presents some common drawbacks of the semiconductor materials since delivers poor reversibility at the chargedischarge process due to the volumetric alteration of the crystalline structure during the redox reactions.…”

“…Besides, it is also considered a ceramic compound, with low electronic conductivity, which is typically mixed by many authors with binders (carbon black, acetylene black or so on) to favor the particles connectivity [12][13][14][15]. The improvement of the microstructure connectivity in PCs is one of the reason why some authors have proposed alternative routes based on different processing strategies such as the inclusion of metal phases in the semiconductor material [10,16], the application of a post-sintering heat treatment after a specific shaping process [17][18][19] or the mentioned combination of the metal oxide with carbon-based materials, such as activated carbon, carbon nanotubes, or other mesoporous materials. Among all of them, graphene-based materials are good candidates due to its two-dimensional hexagonal network and their delocalized electrons shows an elevated electronic conductivity, an intrinsic mechanical strength (flexible material), transparency and high specific surface area, which transform them in promising co-material to fabricate the electrodes with higher electrochemical performances [20,21].…”

Pulsed Reverse Potential Electrodeposition of Carbon-Free Ni/NiO Nanocomposite Thin Film Electrode for Energy Storage Supercapacitor Electrodes

“…These values, revealing high energy storage capacities, are much higher than previously reported values on Ni based energy storage materials [1,11]. For example, Joaquin et al reported 755 Fg −1 at 1 Ag −1 on electrophoretic deposited core shell nanowire arrays of Ni/NiO [12] while Navale et al reported 458 Fg −1 at 1 Ag −1 corresponding to potentiostatic electrodeposited NiO thin films on stainless steel [11]. However, Farrukh et al have previously reported a similar high capacitance value of 2093 F/g on their NiO nanotubes electrochemically deposited on anodized aluminium (AAO) [13].…”

The Effect of the Substrate on the Conductivity of NiO Electrodes in Electrochemical Capacitor Shaped by Electrophoretic Deposition

“…The pseudocapacitor electrochemical behavior of as-prepared electrodes was determined by Electrochemical Impedance Spectroscopy (EIS) in order to determine charge transfer between the active material (NiO) and the collector (substrate) in EPD electrodes. [9]…”