Electroless Deposition of Conformal Nanoscale Iron Oxide on Carbon Nanoarchitectures for Electrochemical Charge Storage

Abstract

We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeO(x)) coatings are generated at the interior and exterior surfaces of macroscopically thick ( approximately 90 microm) carbon nanofoam paper substrates via redox reaction with aqueous K(2)FeO(4). The resulting FeO(x)-carbon nanofoams are characterized as device-ready electrode structures for aqueous electrochemical capacitors and they demonstrate a 3-to-7 fold increase in charge-storage capacity relative to the native carbon nanofoam when cycled in a mild aqueous electrolyte (2.5 M Li(2)SO(4)), yielding mass-, volume-, and footprint-normalized capacitances of 84 F g(-1), 121 F cm(-3), and 0.85 F cm(-2), respectively, even at modest FeO(x) loadings (27 wt %). The additional charge-storage capacity arises from faradaic pseudocapacitance of the FeO(x) coating, delivering specific capacitance >300 F g(-1) normalized to the content of FeO(x) as FeOOH, as verified by electrochemical measurements and in situ X-ray absorption spectroscopy. The additional capacitance is electrochemically addressable within tens of seconds, a time scale of relevance for high-rate electrochemical charge storage. We also demonstrate that the addition of borate to buffer the Li(2)SO(4) electrolyte effectively suppresses the electrochemical dissolution of the FeO(x) coating, resulting in <20% capacitance fade over 1000 consecutive cycles.

Nanostructured Fe2O3–graphene composite as a novel electrode material for supercapacitors

“…To the best of our knowledge, this is the best report for the cycle stability of Fe 2 O 3 -based electrode. Previous studies employing Li 2 SO 4 as electrolyte but the acidity of the lithium sulfate electrolyte is expected to promote reductive dissolution of the Fe 2 O 3 when cycled to progressively negative potentials, with the formation of soluble Fe 2+ species inevitably lead to capacitance loss [27]. In this work, KOH used as electrolyte instead of Li 2 SO 4 because of the K + has a similar hydration ions radius with Li + and Fe 2 O 3 also has a good stability in alkaline electrolyte than in acidic environments.…”

“…Another option that can improve the electrochemical performance is to combine α-Fe 2 O 3 with other components with good conductivity to facilitate the electron transfer between the active materials and the current collector. For example, Long and co-workers described a simple electroless deposition of conformal nanoscale iron oxide on carbon nanofoams for ECs [27]. The resulting FeO x -carbon nanofoams can deliver specific capacitance value of 84 and 300 F g −1 when normalized to the content of FeO x .…”

Supercapacitive behavior of electrosynthesized marygold-like structured nickel doped iron hydroxide thin film

“…The metal hydroxide thin films and powder formed by electrochemical deposition have been explored extensively for energy storage [10,11]. Nagrajan and Zhitomirsky has reported electrodeposited iron oxide electrode for supercapacitor application [12], but charge-storage capacity arises from faradaic pseudocapacitance of the iron oxide delivering specific capacitance normalized to the content of FeOOH, as reported earlier [13,14]. The first task and successful achievement of this concept has been to fabricate the nickel doped iron hydroxide thin film electrode that was capable for supercapacitor application.…”

Electrochemical Characterization of Na-Ion Charge-Storage Properties for Nanostructured NaTi2(PO4)3as a Function of Crystalline Order

“…A borate buffer was added to 1 M Na 2 SO 4 (pH ∼ 5.5) in order to stabilize the pH of the aqueous electrolyte solution to pH ∼ 9, thus suppressing hydrogen evolution reaction at the lower potential limit. 39 Working electrodes for both nonaqueous and aqueous experiments were prepared by casting ∼0.5-1 mg of a carbon composite slurry onto stainless-steel mesh and pressed uniaxially at 8000 psi. The carbon composite slurries contained 70% active material (including rGO), 25% conductive carbon Super P, and 5% polyvinylidene fluoride binder.…”