Solvothermal‐induced construction of ultra‐tiny Fe 2 O 3 nanoparticles/graphene hydrogels as binder‐free high‐capacitance anode for supercapacitors

Three‐dimensional (3D) ultra‐tiny Fe 2 O 3 nanoparticles/graphene hydrogels were prepared using a facile and efficient solvothermal reaction, by which the phase of iron oxide, particle size and the morphology of hydrogels can be precisely controlled by simply adjusting the solvothermal reaction time. Accordingly, the effect of the microstructures of hydrogels on electrochemical performance was systematically studied. It was found that Fe 2 O 3 /rGO‐50 hydrogels (with a solvothermal reaction time of 50 min) possessed a desirable crystallinity, suitable particle size, decent porous structure, large specific surface area and high electrical conductivity, thus exhibiting a superior electrochemical performance as binder‐free anode of supercapacitors: a large potential range of 1.15 V, an ultrahigh specific capacitance of 1090 F·g −1 at a current density of 2 A·g −1 and excellent rate capability (531 F·g −1 at 10 A·g −1 ). The rational design and systematic research of electrode materials will provide new lights for the preparation of advanced electrochemical energy storage devices.