In situ generation of exfoliated graphene layers on recycled graphite rods for enhanced capacitive performance of Ni–Co binary hydroxide

Abstract

A functionalized exfoliated graphite rod (FEGR), with a high surface area, is produced for use as a promising substrate for supercapacitors, via controlled oxidative treatment of a recycled graphite rod of exhausted zinc–carbon batteries.

Promoted glucose electrooxidation at Ni(OH)2/graphene layers exfoliated facilely from carbon waste material

“…2A, the calculated specific capacitance ( C s ) of FEGR using eqn (3) is 5.5 mF cm −2 which is greater than the C s of RGR (0.21 mF cm −2 ) by 26 times.where C s is the specific capacitance in F cm −2 , S is the area of the electrode in cm 2 , ∫ I d t is the integrated oxidation or reduction current–potential area divided by the potential scan rate, and Δ V is the operating potential window in V . 21,43…”

“…The position of the peaks on the CV indicates that the transformation of Ni(OH) 2 to NiOOH is a diffusion-controlled process. 2,21 To confirm that this transformation is a diffusion-controlled process, the study of the effect of potential scan rate ( v ) on the current peak ( I p ) was done. By plotting I p against the v 0.5 (see Fig.…”

“…where C s is the specic capacitance in F cm −2 , S is the area of the electrode in cm 2 , Ð I dt is the integrated oxidation or reduction current-potential area divided by the potential scan rate, and DV is the operating potential window in V. 21,43 The high specic capacitance of the FEGR support is re-ected in, the large adsorption capacity of this large activated electrode's surface to ingest a large number of electrolyte species by supplying a rough surface, a large number of the homogeneous-distributed grooves on the surface of the electrode, in addition to the large produced number of expanded graphene sheets.…”

“…SO 4 2− , Cl − , NO 3 − , and CH 3 COO − ) between the hydroxide layers. [21][22][23] b-Ni(OH) 2 has a lower theoretical oxidation potential than a-Ni(OH) 2 and thus has higher catalytic activity toward GOR into gluconolactone, as demonstrated by El-Nagar. 14 However, it is sometimes found that the a-Ni(OH) 2 showed higher catalytic activity than b-NiOOH because of its morphology and the large d-spacing that facilitates the access of electrolyte ions to its active sites thus being converted to the g-NiOOH which oxidizes the glucose.…”

“…Interestingly, Ni(OH) 2 has two polymorphic crystal structures, a-Ni(OH) 2 phase with hydrotalcite-like structure and b-Ni(OH) 2 with brucite-like structure (see Scheme 1). [21][22][23] a-Ni(OH) 2 has a higher d-spacing value with the turbostratically crystallized structure due to the presence of the water molecules and/or anions (e.g. SO 4 2− , Cl − , NO 3 − , and CH 3 COO − ) between the hydroxide layers.…”