Nanocrystalline FeWO4 as a pseudocapacitive electrode material for high volumetric energy density supercapacitors operated in an aqueous electrolyte

• FeWO4 was investigated as a pseudocapacitive electrode material.
• It clearly displays a pseudocapacitive behavior in a neutral aqueous electrolyte.
• A high volumetric capacitance of 210 F·cm− 3 was achieved at 20 mV·s− 1.
• An excellent cycling ability is obtained in the potential range of − 0.6/0 V vs. Ag/AgCl.

Iron tungstate (FeWO4) has been synthesized using two low-temperature synthetic routes and investigated as a new pseudocapacitive electrode material for supercapacitors operating in a neutral aqueous electrolyte. Its electrochemical properties are clearly related to the specific surface area and seem to originate from Fe3 +/Fe2 + fast surface reactions. For FeWO4 obtained by polyol-mediated synthesis, a high volumetric capacitance of 210 F·cm− 3 (i.e. more than two times higher than that of activated carbon) was measured at 20 mV·s− 1 with less than 5% fade over 10,000 cycles. Furthermore, unlike most of the previously investigated iron based electrodes, a unique pseudocapacitive behavior is observed, thus emphasizing the role of the crystallographic structure on the electrochemical signature.

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