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

Nowadays, the glucose electro-oxidation reaction (GOR) is considered one of the most important solutions for environmental pollution. The GOR is the anodic reaction in direct glucose fuel cells and hybrid water electrolysis. In this study, the GOR is boosted using a carbon support modified with Ni(OH)2 as a non-precious catalyst. The carbon support, with in situ generated graphene nanosheets having a large surface area, grooves, and surface functional groups, is prepared via a simple electrochemical treatment of the carbon rods of an exhausted zinc-carbon battery. Ni(OH)2 is electrodeposited on the surface of the functionalized exfoliated graphite rod (FEGR) via the dynamic hydrogen bubbling technique (DHBT) and tested for GOR. The thus-prepared Ni(OH)2/FEGR electrode is characterized by SEM, mapping EDX, HR-TEM, XRD, and XPS characterization tools. Ni(OH)2/FEGR displays an onset potential of 1.23 V vs. the reversible hydrogen electrode (RHE) and attains high current densities at lower potentials. Additionally, Ni(OH)2/FEGR showed prolonged stability toward GOR by supporting a constant current over a long electrolysis time. The enhanced catalytic performance is attributed to the superb ionic and electronic conductivity of the catalyst. Importantly, ionic conductivity increased, due to (i) a large surface area of in situ generated graphene layers, (ii) enhanced distribution of active material during deposition using DHBT, and (iii) increased hydrophilicity of the underlying substrate. Therefore, the Ni(OH)2/FEGR electrode can be used efficiently for GOR as a low-cost catalyst, achieving low onset potential and high current densities at low potentials.

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

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. SEM, EDX, XPS, FT-IR, Raman, and contact angle measurements are carried out to disclose the surface characteristics of the FEGR. The surface of the FEGR is characterized by in situ generated grooves, together with graphene layers which are directly attached to the underlying graphite base. The FEGR electrodes enhance the capacitive performance of Ni(OH)2 and binary Ni-Co(OH)2. The Ni-Co(OH)2/FEGR electrode displays a superb specific capacity value (2552.6 C g-1) at a current density of 5 A g-1 and this value is retained to 70.8% at a high current density of 50 A g-1 indicating the outstanding rate performance of this electrode material. This enhanced behavior is attributed to the facile interaction of electrolyte species, even at high current density, with the active sites of the redox catalyst layer (distributed over a larger fraction of the underlying substrate with enhanced hydrophilicity). Moreover, the excellent electrical conductivity of the in situ surface generated graphene layers is another promoting factor.