Hybrid Films of Ni(OH)₂ Nanowall Networks on Reduced Graphene Oxide Prepared at a Liquid/Liquid Interface for Oxygen Evolution and Supercapacitor Applications

Abstract

Free‐standing films of reduced graphene oxide (rGO) based Ni(OH)2 nanowall structures are generated at a liquid/liquid interface involving in situ reaction and self‐assembly. The nanowall network of Ni(OH)2 sheets anchored on rGO layers with 10–15 nm wall thickness and ordered voids of average size 100 nm can serve as excellent candidates for catalyzing electrochemical oxygen evolution reaction (OER) as they expose maximum edge sites of Ni(OH)2 and allow diffusion and penetration of electrolytes into voids enhancing the contact area of the electrolyte/electrocatalyst interface. The unique morphology of the hybrid films exhibited high electrochemical surface area and low charge transfer resistance. Accordingly, rGO−Ni(OH)2 hybrid films display excellent catalytic activity and high cycling stability in alkaline solutions giving a current density of 10 mA cm−2 at an overpotential of 378 mV with a Tafel slope of 56 mV dec−1. The hybrid films also exhibited a high specific and areal capacitance of 1402 Fg−1 and 98.12 mF cm−2 at a scan rate of 5 mVs−1. OER activity and capacitance of the hybrid rGO−Ni(OH)2 films are higher compared to that of bare Ni(OH)2 film and is attributed to the synergic effect between the rGO layer and the ordered interconnected nanowall Ni(OH)2 nanostructures. The primary advantage of these hybrid films is that they can be collected on the desired substrate for ready use as electrodes without the use of any external binders.

Synthesis of nickel hydroxide/reduced graphene oxide composite thin films for water splitting application

“…40 corresponding to D band and G band of graphene, which is consistent with Raman spectrum of rGO. 22 The above analysis indicate the synthesis of Ni(OH) 2 /rGO composite film. Figure 4A).…”

“…20 To improve the electrocatalytic performance, various strategies are used such as doping the transition metals such as V, Fe, Co, 3,17,18 or hybridizing the conductive substrate using carbon nanotube, 21 and graphene derivatives. 22,23 For instance, the V doped Ni(OH) 2 nanostructure was prepared using the chemical bath deposition technique, which showed enhanced OER performance with overpotential of 268 mV @10 mA cm −2 . After V doping, the gallery space and electrical conductivity is increased.…”

“…3 The use of reduced graphene oxide (rGO)-based OER electrocatalysts has shown higher advantages because it has better conductivity and higher electrochemical surface area as well as good mechanical strength. [22][23][24] There are two strategies to fabricate a highly efficient Ni(OH) 2 /rGO composite electrode. In first route, the nanostructured Ni(OH) 2 and rGO nanosheets are mixed together and coated on the substrate using a binder.…”

“…25 Similarly, the rGO-based Ni(OH) 2 nanowall structures by liquid-liquid interface method exhibit 378 mV overpotential to reach a current density of 10 mA cm −2 , while bare Ni(OH) 2 film shows 421 mV overpotential to reach same current density. 22 In the above synthesis process, there is no tight contact between electrode and free-standing film. Hence, the electrode/electrolyte interface resistance or charge transfer resistance (R ct ) was increased, which deteriorates the electrocatalytic performance.…”

Nickel Cobalt Phosphite Nanorods Decorated with Carbon Nanotubes as Bifunctional Electrocatalysts in Alkaline Medium with a High Yield of Hydrogen Peroxide

“…Hence, alternative low cost and earth abundant catalysts based on non‐precious transition metal oxides and hydroxides (Ni(OH) 2 , Co(OH) 2 , MoO 2 , MoO 3, WO 3 , etc.) and dichalcogenides MoS 2 , CoS 2 are explored for electrocatalysis . Recently, transition metal salts of phosphorous oxy acids have gained more attention towards electrocatalytic applications due to their earth abundance, low cost, environmentally benign nature and high efficiency.…”