Jay F. Whitacre

Electrochemically active nitrogen-enriched nanocarbons with well-defined morphology synthesized by pyrolysis of self-assembled block copolymer.

Novel nanoporous nitrogen-enriched carbon materials were prepared through a simple carbonization procedure of well-defined block copolymer precursors containing the source of carbon, i.e., polyacrylonitrile (PAN), and a sacrificial block, i.e., poly(n-butyl acrylate) (PBA). The preparation of nitrogen-enriched nanocarbons with hierarchical pore structure was enabled by the high fidelity preservation of the initial phase-separated nanostructure between two polymer blocks upon carbonization. Supercapacitors fabricated from the prepared carbons exhibited unusually high capacitance per unit surface area (>30 μF/cm(2)) which was attributed to the pseudocapacitance resulting from the high nitrogen content originating from the PAN precursor. Electrochemical availability of the nitrogen species was also evident from the results of oxygen reduction experiments. The hierarchical pore structure and the high nitrogen content in such materials make them particularly promising for use in supercapacitor and electrocatalyst applications.

Biologically derived melanin electrodes in aqueous sodium-ion energy storage devices

Significance Here we present important findings related to biologically derived pigments for potential use as battery electrodes. Namely, we report the synthesis, fabrication, and characterization of melanins as materials for use in aqueous sodium-ion batteries. We demonstrate the use of naturally occurring melanins as active electrode materials in charge storage devices. Furthermore, the performance of melanin anodes is comparable to many commonly available synthetic organic electrode materials. The structure–property relationships that govern the storage capacity in melanin materials were also elucidated. These findings suggest that the unique chemistry and nanostructure in natural melanins increase the charge storage capacity compared with synthetic melanin analogues. Biodegradable electronics represents an attractive and emerging paradigm in medical devices by harnessing simultaneous advantages afforded by electronically active systems and obviating issues with chronic implants. Integrating practical energy sources that are compatible with the envisioned operation of transient devices is an unmet challenge for biodegradable electronics. Although high-performance energy storage systems offer a feasible solution, toxic materials and electrolytes present regulatory hurdles for use in temporary medical devices. Aqueous sodium-ion charge storage devices combined with biocompatible electrodes are ideal components to power next-generation biodegradable electronics. Here, we report the use of biologically derived organic electrodes composed of melanin pigments for use in energy storage devices. Melanins of natural (derived from Sepia officinalis) and synthetic origin are evaluated as anode materials in aqueous sodium-ion storage devices. Na+-loaded melanin anodes exhibit specific capacities of 30.4 ± 1.6 mAhg−1. Full cells composed of natural melanin anodes and λ-MnO2 cathodes exhibit an initial potential of 1.03 ± 0.06 V with a maximum specific capacity of 16.1 ± 0.8 mAhg−1. Natural melanin anodes exhibit higher specific capacities compared with synthetic melanins due to a combination of beneficial chemical, electrical, and physical properties exhibited by the former. Taken together, these results suggest that melanin pigments may serve as a naturally occurring biologically derived charge storage material to power certain types of medical devices.

Optimal Plug-In Hybrid Electric Vehicle Design and Allocation for Minimum Life Cycle Cost, Petroleum Consumption, and Greenhouse Gas Emissions

Plug-in hybrid electric vehicle (PHEV) technology has the potential to reduce operating cost, greenhouse gas (GHG) emissions, and petroleum consumption in the transportation sector. However, the net effects of PHEVs depend critically on vehicle design, battery technology, and charging frequency. To examine these implications, we develop an optimization model integrating vehicle physics simulation, battery degradation data, and U.S. driving data. The model identifies optimal vehicle designs and allocation of vehicles to drivers for minimum net life cycle cost, GHG emissions, and petroleum consumption under a range of scenarios. We compare conventional and hybrid electric vehicles (HEVs) to PHEVs with equivalent size and performance (similar to a Toyota Prius) under urban driving conditions. We find that while PHEVs with large battery packs minimize petroleum consumption, a mix of PHEVs with packs sized for 25– 50 miles of electric travel under the average U.S. grid mix (or 35– 60 miles under decarbonized grid scenarios) produces the greatest reduction in life cycle GHG emissions. Life cycle cost and GHG emissions are minimized using high battery swing and replacing batteries as needed, rather than designing underutilized capacity into the vehicle with corresponding production, weight, and cost implications. At 2008 average U.S. energy prices, Li-ion battery pack costs must fall below

Net air emissions from electric vehicles: the effect of carbon price and charging strategies.

590/kW h at a 5% discount rate or below

Relating Synthesis Conditions and Electrochemical Performance for the Sodium Intercalation Compound Na4Mn9O18 in Aqueous Electrolyte

410/kW h at a 10% rate for PHEVs to be cost competitive with HEVs. Carbon allowance prices offer little leverage for improving cost competitiveness of PHEVs. PHEV life cycle costs must fall to within a few percent of HEVs in order to offer a cost-effective approach to GHG reduction. DOI: 10.1115/1.4002194

Catechol-Mediated Reversible Binding of Multivalent Cations in Eumelanin Half-Cells

Plug-in hybrid electric vehicles (PHEVs) may become part of the transportation fleet on time scales of a decade or two. We calculate the electric grid load increase and emissions due to vehicle battery charging in PJM and NYISO with the current generation mix, the current mix with a

Self-deployable current sources fabricated from edible materials

50/tonne CO(2) price, and this case but with existing coal generators retrofitted with 80% CO(2) capture. We also examine all new generation being natural gas or wind+gas. PHEV fleet percentages between 0.4 and 50% are examined. Vehicles with small (4 kWh) and large (16 kWh) batteries are modeled with driving patterns from the National Household Transportation Survey. Three charging strategies and three scenarios for future electric generation are considered. When compared to 2020 CAFE standards, net CO(2) emissions in New York are reduced by switching from gasoline to electricity; coal-heavy PJM shows somewhat smaller benefits unless coal units are fitted with CCS or replaced with lower CO(2) generation. NO(X) is reduced in both RTOs, but there is upward pressure on SO(2) emissions or allowance prices under a cap.

Evaluation of a proposal for reliable low-cost grid power with 100% wind, water, and solar

The sodium intercalation compound Na 4 Mn 9 O 18 , more commonly Na 0.44 MnO 2 , was studied as a potential positive electrode in an aqueous electrolyte hybrid energy storage device. Varying ratios of precursors were used in a solid-state synthetic route in an effort to compensate for volatile loss of sodium during processing. The powders were characterized using X-ray powder diffraction and thermogravimetric analysis, while particle morphology and formation were studied by scanning electron microscopy/electron dispersive spectroscopy and transmission electron microscopy. Electrochemical behavior was characterized by galvanostatic cycling and cyclic voltammetry. With a positive electrode voltage window of -0.3 to 0.3 V vs a Hg/HgSO 4 reference electrode, a specific capacity of 35 mAh/g was observed after 20 cycles at a C/1.4 rate (25 mA/g) with little capacity loss. The most stable of the materials were made with a Na:Mn precursor ratio equal to 0.55 and showed excellent performance through many charge/ discharge cycles. These samples also contained varying amounts of β-Na 0.70 MnO 2 and α-Mn 2 O 3 impurity phases. The results indicated a relationship between the precursor Na/Mn ratio and the resultant redox potentials associated with the multiple hybrid Mn oxidation states encountered during cycling although no significant variance in the crystallography of the Na 0.44 MnO 2 phase was observed.

Evidence of Porphyrin‐Like Structures in Natural Melanin Pigments Using Electrochemical Fingerprinting

Electrochemical storage systems that utilize divalent cations such as Mg2+ can improve the volumetric charge storage capacities compared to those that use monovalent ions. Here, a cathode based on naturally derived melanin pigments is used in secondary Mg2+ batteries. Redox active catechol groups in melanins permit efficient and reversible exchange of divalent Mg2+ cations to preserve charge storage capacity in biopolymer cathodes for more than 500 cycles.

Relating Precursor Pyrolysis Conditions and Aqueous Electrolyte Capacitive Energy Storage Properties for Activated Carbons Derived from Anhydrous Glucose-d

Flexible biodegradable electronics have the potential to serve as the centerpiece for temporary electronically active medical implants. Biodegradable electronics may exhibit many advantages over traditional chronic implants. Two important long-term goals for biodegradable electronics are (1) supplying sufficient power and (2) reducing the invasiveness of device deployment. Edible electronic devices are capable of addressing both challenges. Here, we introduce electrochemical electronic power sources that are compatible with non-invasive deployment strategies and are composed entirely of edible materials and naturally occurring precursors that are consumed in common diets. The current sources developed herein are powered by onboard sodium ion electrochemical cells. Potentials up to 0.6 V and currents in the range of 5-20 μA can be generated routinely. These devices could serve as an enabling platform technology for edible electronics used in non-invasive sensing and stimulation of tissues within the human body.