Bullet-like microstructured nickel ammonium phosphate/graphene foam composite as positive electrode for asymmetric supercapacitors

• Published in: RSC advances 2020-04, Vol.1 (28), p.16349-1636
• Main Authors: Mahmoud, Badr A, Mirghni, Abdulmajid A, Fasakin, Oladepo, Oyedotun, Kabir O, Manyala, Ncholu
• Format: Article
• Language: English
• Subjects: Activated carbon; Ammonium phosphates; Asymmetry; Chemistry; Composite materials; Crystal structure; Electrodes; Graphene; Gravimetry; Hydrothermal crystal growth; Morphology; Nickel; Raman spectroscopy; Supercapacitors
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d0ra02300k

Unique microstructured nickel ammonium phosphate Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O and Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O/GF composite were successfully synthesized through the hydrothermal method with different graphene foam (GF) mass loading of 30, 60 and 90 mg as a positive electrode for asymmetric supercapacitors. The crystal structure, vibrational mode, texture and morphology of the samples were studied with X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and scanning electron microscopy (SEM). The prepared materials were tested in both 3-and 2-electrode measurements using 6 M KOH electrolyte. The composite material Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O/60 mg exhibited a remarkable gravimetric capacity of 52 mA h g −1 , higher than the 34 mA h g −1 obtained for the Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O pristine sample, both at 0.5 A g −1 . For the fabrication of the asymmetric device, activated carbon from pepper seed (ppAC) was used as a negative electrode while Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O/60 mg GF was adopted as the positive electrode. The Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O/60 mg GF//ppAC asymmetric device delivered a specific energy of 52 Wh kg −1 with an equivalent specific power of 861 W kg −1 at 1.0 A g −1 within a potential range of 0.0-1.5 V. Moreover, the asymmetric device displayed a capacity retention of about 76% for over 10 000 cycles at a high specific current of 10.0 A g −1 . Unique morphology of (Ni(NH 4 ) 2 (PO 3 ) 4 ·4H 2 O/60GF) as a positive electrode for high-performance asymmetric supercapacitors.