Eg c2h6o2

36 g of Ni(NO₃)₂.6H₂O (Sigma-Aldrich) was added to 18 mL of EG (C₂H₆O₂) (Sigma-Aldrich) and ultra-sonicated for 1 hour. After that the resultant mixture was poured into a cylindrical crystalline glass dish, which was pre-heated to a temperature of 300 °C for 30 minutes by using a hot plate in the ambient atmosphere. A sudden introduction of reactants in to the hot glass dish leads to the evolution of NO₂ gas bubbles and subsequent production of fluffy Ni sponge. Cobalt oxide (Co₃O₄) sponge was prepared by the reaction of Co(NO₃)₂.6H₂O (36 g) and EG (18 mL) by using the same procedure mentioned above for Ni sponge. The same synthesis route is followed for the preparation of Ni-Co alloy sponges. Here reactants Ni(NO₃)₂.6H₂O and Co(NO₃)₂.6H₂O (sigma-Aldrich), were mixed together taking a total amount of 36 g in the weight ratio of 1:1, 1:2 and 2:1 and the resulting sponges named as Ni₁Co₁, Ni₁Co₂ and Ni₂Co₁. For the synthesis of Ni-NG, 36 g of Ni(NO₃)₂.6H₂O (Sigma-Aldrich) and 100 mg of NG(prepared by heating GO with melamine (1:5 ratio) for 3 hrs at 800 °C)51 (link) were added to 18 mL of EG (C₂H₆O₂) (Sigma-Aldrich) and ultra-sonicated for 1 hour. The resultant mixture was poured in to a cylindrical dish preheated for 1 hour leads to the formation of Ni-NG sponges.

Highly ordered and vertically oriented TNTs were prepared by anodization of Ti (titanium foil, 0.25-mm thickness, 99.7% purity; Sigma-Aldrich, St. Louis, MO, USA) sheets in an electrolyte consisting of 0.25 wt.% ammonium fluoride (NH₄F) (98 + % purity; Sigma-Aldrich) and 0.5 wt.% distilled (DI) water in ethylene glycol (EG) (C₂H₆O₂, 99.0% purity; Sigma-Aldrich) at 40 V for 8 h. A detailed experimental procedure has been described in our previous paper
[25 (link)]. After anodization, the samples were washed with DI water to remove the occluded ions and dried in a N₂ stream. Finally, the samples were annealed at 450°C for 2 h with a heating rate of 5°C min^-1 at ambient conditions.