Electrochemical properties and mechanism of CoMoO4@NiWO4 core-shell nanoplates for high-performance supercapacitor electrode application studied via in situ X-ray absorption spectroscopy.

Binary transition metal oxide CoMoO4@NiWO4 core-shell nanoplates grown directly on Ni foam have been synthesized with a facile two steps hydrothermal process. The high electrochemical surface area (2933 cm2) core-shell nanoplates demonstrate excellent electrochemical properties (areal capacity as high as 0.464 mAh cm−2 at a current density of 5 mA cm−2) and great cycle stability (92.5 % retention after 3000 cycles with a high current density of 40 mA cm−2). The mechanism of the electrochemical reaction, based on by using in-situ X-ray absorption spectroscope technique, clearly shows that the Co and Ni elements simultaneously participate in a faraday reaction with the electrolyte. These results indicate that the excellent electrochemical performance than CoMoO4 nanoplates is attributed to a large electrochemical surface area and a synergistic effect between NiWO4 and CoMoO4. This combination of two binary transition metal oxides can hence provide an excellent route to develop a high-performance electrode material for supercapacitor applications.