Graphitized porous silicon decorated with cobalt hexacyanoferrate nanocubes as hybrid electrode for high-performance supercapacitors

In this work, we report a scalable route to wafer-size processing for fabrication of hybrid nanocomposite electrodes based on cobalt hexacyanoferrate/carbon/porous silicon (CoHCF/C/Si) to improve the performances of silicon-based supercapacitors via electrochemical processes. First, an electrochemical etching process was used to obtain a 3D nanopomus matrix on the top of silicon wafer, and the resulted huge surface was then covered with active nanomaterials by the successive electrochemical deposition of an ultra-thin carbon layer and CoHCF nanocubes, respectively. The fabricated symmetric supercapacitor device showed excellent volumetric capacitance of about 5 F cm(-3) at the current density of 0.7 mA cm(-2), an outstanding volumetric power density of 19.42 W cm(-3) with a high energy density of 0.98 mWh cm(-3), achieving good cycling stability with a capacitance retention of 61% after 5000 cycles at a high rate of discharge current density, 100 A g(-1). The nanosized CoHCF phase favors migration of Li+ ions into the material, followed by charge transfer reactions via insertion/extraction of alkaline ions into/from the cyano-bridged framework during the redox reactions of Fe-II/(III) and Co(II/III )ions as evidenced by CV and GCD. These results support the successful integration of CoHCF nanocubes with carbonaceous and silicon material using electrochemical methods, rendering synergistic effects over the electrochemical performances.