Cobalt hydroxide nanoflakes and their application as supercapacitors and oxygen evolution catalysts

Abstract

Finding alternative routes to access and store energy has become a major issue recently. Transition metal oxides have shown promising behaviour as catalysts and supercapacitors. Recently, liquid exfoliation of bulk metal oxides appears to be an effective route which provides access to two-dimensional (2D) nano-flakes, the size of which can be easily selected. These 2D materials exhibit excellent electrochemical charge storage and catalytic activity for the oxygen evolution reaction. In this study, various sized selected cobalt hydroxide nano-flake materials are fabricated by this time efficient and highly reproducible process. Subsquently, the electrochemical properties of the standard size Co(OH) nanoflakes were investigated. The oxide modified electrodes were prepared by spraying the metal oxide flake suspension onto a porous conductive support electrode foam, either glassy carbon or nickel. The cobalt hydroxide/nickel foam system was found to have an overpotential value at 10 mA cm in 1 M NaOH as low as 280 mV and an associated redox capacitance exhibiting numerical values up to 1500 F g, thereby making it a viable dual use electrode.

Layered and two dimensional metal oxides for electrochemical energy conversion

“…The Co(OH) 2 on the GC had an improved OER performance by 57% compared to the bare GC, while the Co(OH) 2 /Ni achieved a 30% increase over the bare Ni support. 79 Interestingly, the Co(OH) 2 on the Ni foam behaved as a better OER electrocatalyst when compared to the exfoliated Ni(OH) 2 on the same Ni foam support previously discussed in this review by the same group. 78 However, regardless of the actual OER performance values, it is clear that the nature of the support plays a role in the activity of layered TMO material.…”

“…103 In a subsequent report by the same group, the exfoliated Co(OH) 2 was deposited onto two different types of high area supports; glassy carbon (GC) foam and nickel (Ni) foam. 79 The results reveal the exfoliated Co(OH) 2 on the Ni foam was a superior electrode when compared to the same material on the GC foam in terms of absolute OER overpotetnial i.e. the overpotential at 10 mA cm À2 .…”

“…Liquid phase exfoliation (LPE) of Ni(OH) 2 and Co(OH) 2 layered materials has been reported to increase the activity of these materials for the OER compared to their layered stucture. 76,78,79 For example, Ni(OH) 2 exfoliated by LPE in a iso-propyl alcohol (IPA) dispersion was deposited onto Ni foam by a spraying technique and the OER performance was analysed in 1 M NaOH, Fig. 6(A).…”

“…7(A-E). 76,79 After exfoliation, extensive material characterisation was carried out on the Co(OH) 2 to reveal that, unlike the exfoliated Ni(OH) 2 , XPS showed a slight change in the chemical environment for the Co(OH) 2 exfoliated materials, Fig. 7(G and H).…”

Molybdenum Disulphide Heterointerfaces as Potential Materials for Solar Cells, Energy Storage, and Hydrogen Evolution

“…The nanostructures possess many of these features and hence can be the potential candidates for supercapacitor electrodes. The recent work in this direction can be broadly classified into three main categories: 1) carbon‐based materials which include graphene, nanotubes, and activated carbon and their composites; 2) transition metal oxides and metal hydroxides, these include PbO, NiO, MnO 2 , MoO 3 , RuO 2 , CuO, and other metal oxides and metal hydrides such as Co(OH) 2 , Ni(OH) 2 , respectively; and 3) conducting polymers and their composites with various metals and metal oxides . In some of these systems, a significant increase in specific capacitance has been reported.…”