There are an increasing number of studies regarding active electrode materials that undergo faradaic reactions but used for electrochemical capacitor applications. Unfortunately, some these described as "pseudocapacitive" despite the fact their signature (e.g., cyclic voltammogram and charge/discharge curve) is analogous to a "battery" material, commonly observed Ni(OH)2 cobalt oxides in KOH electrolyte. Conversely, true pseudocapacitive such MnO2 display behavior typical capacitive carbon...

The next generation of high-performance batteries should include alternative chemistries that are inherently safer to operate than nonaqueous lithium-based batteries. Aqueous zinc-based can answer challenge because monolithic zinc sponge anodes be cycled in nickel-zinc alkaline cells hundreds thousands times without undergoing passivation or macroscale dendrite formation. We demonstrate the three-dimensional (3D) form-factor elevates performance three fields use: (i) >90% theoretical depth...

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The self-limiting reaction of aqueous permanganate with carbon nanofoams produces conformal, nanoscopic deposits birnessite ribbons and amorphous MnO2 throughout the ultraporous structure. coating contributes additional capacitance to nanofoam while maintaining favorable high-rate electrochemical performance inherent structure nanofoam. Such a three-dimensional design exploits benefits MnO2-carbon interface produce an exceptionally high area-normalized (1.5 F cm-2), as well volumetric (90 cm-3).

Pt−Ru is the favored anode catalyst for oxidation of methanol in direct fuel cells (DMFCs). The nanoscale blacks are accepted to be bimetallic alloys as based on their X-ray diffraction patterns. Our bulk and surface analyses show that although practical have patterns consistent with an alloy assignment, they primarily a mix Pt metal Ru oxides plus some only small amounts metal. Thermogravimetric analysis photoelectron spectroscopy as-received electrocatalysts indicate DMFC materials contain...

Zinc-based replacements for Li-ion batteries are now feasible by using 3D-interconnected Zn sponges that suppress dendrite formation when cycled.

Manganese oxides have a relatively long history in the world of battery chemistry, dating back to work Leclanché 1860s, which ultimately formed basis for now-ubiquitous primary 1.5 V Zn/MnO 2 alkaline cell.

Pseudocapacitive charge storage is based on faradaic charge-transfer reactions occurring at the surface or near-surface of redox-active materials. This property great interest for electrochemical capacitors because substantially higher capacitance obtainable as compared to traditional double-layer electrode processes. While high levels pseudocapacitance have been obtained with nanoscale materials, development practical structures that exhibit pseudocapacitive properties has challenging. The...

Over the past decade, interest in electrochemical capacitors as an energy-storage technology has increased enormously, spurring development and evaluation of a large number new materials device configurations. This perspective article aims to propose guidelines by which devices should be evaluated, how resulting data reported with respect critical metrics such capacitance, energy power.

Contrary to the current understanding of Pt−Ru electrocatalyzed oxidation methanol, bimetallic alloy is not most desired form catalyst. In nanoscale blacks used electrooxidize methanol in direct fuel cells, Pt0Ru0 has orders magnitude less activity for than does a mixed-phase electrocatalyst containing Pt metal and hydrous ruthenium oxides (RuOxHy). Bulk, rather near-surface, quantities electron−proton conducting RuOxHy are required achieve high oxidation. The active catalyst forms...

Ruthenium dioxide is an important electrode material for applications in electrocatalysis and power sources. High surface areas are achieved hydrous RuO2 precipitates mixed ruthenium oxide−titanium oxide, (Ru−Ti)Ox, aerogels (in which nanoscale domains networked to form a highly porous structure). The electrochemical properties of (Ru−Ti)Ox aerogels, RuO2, examined by direct pressing sub-milligram quantities the solid onto conductive carbon/wax composite. Voltammetric measurements acidic...

Nanocrystalline ceria is under study to improve performance in high-temperature catalysis and fuel cells. We synthesize porous monolithic nanoarchitectures by reacting Ce(III) salts epoxide-based proton scavengers. Varying the means of pore-fluid removal yields with different pore−solid structures: aerogels, ambigels, xerogels. The dried gels are initially X-ray amorphous, high-surface-area materials, aerogel exhibiting 225 m2 g-1. Calcination produces nanocrystalline materials that,...

Transition metal oxides that mix electronic and ionic conductivity are essential active components of many electrochemical charge-storage devices, ranging from primary alkaline cells to more advanced rechargeable Li-ion batteries. In these charge storage occurs via cation-insertion/deinsertion mechanisms in conjunction with the reduction/oxidation sites oxide. Batteries incorporate such typically designed for high specific energy, but not necessarily power. Electrochemical capacitors (ECs),...

We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeOx) coatings are generated at the interior and exterior surfaces of macroscopically thick (∼90 μm) carbon nanofoam paper substrates via redox reaction with aqueous K2FeO4. The resulting FeOx-carbon nanofoams characterized as device-ready electrode structures for electrochemical capacitors they demonstrate 3-to-7 fold increase in charge-storage capacity relative to native when cycled...

Carbon nanoarchitectures are versatile platforms for advanced electrode structures in which the carbon edifice serves multiple simultaneous functions: a massively parallel 3-D current collector with an interpenetrating structural flow field that facilitates efficient transport of electrons, ions, and molecules throughout structure further functionalization or high-performance electrochemical operation. We fabricate nanofoam papers by infiltrating commercially available low-density fiber...

Electrochemical energy storage arises from processes that are broadly categorized as capacitive, pseudocapacitive, or battery-like. Advanced charge-storing materials designed to deliver high capacity at a rate often exhibit multiplicity of such mechanisms, which complicates the understanding their charge-storage behavior. Herein, we apply "3D Bode analysis" technique identify key descriptors for fast Li-ion processes, where AC impedance data, real capacitance (C') phase angle (ϕ),...

Nanoscale MnO<italic>x</italic> expressed in 3D carbon nanofoam electrodes exhibits both pseudocapacitive and battery-like charge-storage using a mixed Na⁺ : Zn²⁺ aqueous electrolyte.

We have developed crystalline nanoarchitectures of iron oxide that exhibit superparamagnetic behavior while still retaining the desirable bicontinuous pore-solid networks and monolithic nature an aerogel. Iron aerogels are initially produced in X-ray-amorphous, high-surface-area form, by adapting recently established sol-gel methods using Fe(III) salts epoxide-based proton scavengers. Controlled temperature/atmosphere treatments convert as-prepared into nanocrystalline forms with inverse...

Ultraporous aperiodic solids, such as aerogels and ambigels, are sol–gel-derived equivalents of architectures. The walls defined by the nanoscopic, covalently bonded solid network gel. vast open, interconnected space characteristic a building is represented three-dimensionally continuous nanoscopic pore network. We discuss how an architectural construct serves powerful metaphor that guides chemist in design aerogel-like nanoarchitectures their physical chemical transformation into...