α-NiO/Ni(OH)₂/AgNP/F-Graphene Composite for Energy Storage Application

The α-NiO/Ni(OH)₂/AgNP/F-graphene composite, which is silver nanoparticles preanchored on the surface of fluorinated graphene (AgNP/FG) and then added to α-NiO/Ni(OH)₂, is investigated as a potential battery material. The addition of AgNP/FG endows the electrochemical redox reaction of α-NiO/Ni(OH)₂ with a synergistic effect, resulting in enhanced Faradaic efficiency with the redox reactions of silver accompanied by the OER and the ORR. It resulted in enhanced specific capacitance (F g^-1) and capacity (mA h g^-1). The specific capacitance of α-NiO/Ni(OH)₂ increased from 148 to 356 F g^-1 with the addition of AgNP(20)/FG, while it increased to 226 F g^-1 with the addition of AgNPs alone without F-graphene. The specific capacitance of α-NiO/Ni(OH)₂/AgNP(20)/FG further increased up to 1153 F g^-1 with a change in the voltage scan rate from 20 to 5 mV/s and the Nafion-free α-NiO/Ni(OH)₂/AgNP(20)/FG composite. In a similar trend, the specific capacity of α-NiO/Ni(OH)₂ increased from 266 to 545 mA h g^-1 by the addition of AgNP(20)/FG. The performance of hybrid Zn-Ni/Ag/air electrochemical reactions by α-NiO/Ni(OH)₂/AgNP(200)/FG and Zn-coupled electrodes indicates a potential for a secondary battery. It results in a specific capacity of 1200 mA h g^-1 and a specific energy of 660 W h kg^-1, which is divided into Zn-Ni reactions of ∼95 W h kg^-1 and Zn-Ag/air reactions of ∼420 W h kg^-1, while undergoing a Zn-air reaction of ∼145 W h kg^-1.