High-performance energy storage of Ag-doped Co(OH)2-coated graphene paper: In situ electrochemical X-ray absorption spectroscopy.

Layered α-Co(OH) 2 nanosheets have been widely investigated as one of the promising supercapacitor materials owing to its high theoretical specific capacitance (3,460 F g −1 ). However, their poor electrical conductivity, poor stability, and unclear charge storage mechanism limit their practical use in energy storage systems. To address the first two drawbacks of layered Co(OH) 2 , conductive silver nanoparticles (AgNPs) with a finely tuned loading content were for the first time incorporated to the layered Co(OH) 2 structure coated on a flexible reduced graphene oxide (rGO)paper substrate. In situ electrochemical X-ray absorption spectroscopy (XAS) was also used to investigate the charge storage mechanism of AgNPs/Co(OH) 2 electrode. It was found that the incorporation of AgNPs with an average diameter of <10 nm can significantly enhance the charge storage capacity of Co(OH) 2 due to high electrical conductivity leading to fast charge transport. The charge storage mechanism of the Ag-doped α - Co(OH) 2 energy storage cell is based on an intercalation/de-intercalation process (a battery-like behavior) and a physical adsorption of solvated ions (a supercapacitor-like behavior). The incorporation of AgNPs to the layered Co(OH) 2 nanosheets in this work can overcome the current drawbacks of the Co(OH) 2 , which may lead to practical use as a hybrid energy storage device. [ABSTRACT FROM AUTHOR]