Matthew Lefler

Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion and Sodium-Ion Battery Anodes

The cost and practicality of greenhouse gas removal processes, which are critical for environmental sustainability, pivot on high-value secondary applications derived from carbon capture and conversion techniques. Using the solar thermal electrochemical process (STEP), ambient CO2 captured in molten lithiated carbonates leads to the production of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) at high yield through electrolysis using inexpensive steel electrodes. These low-cost CO2-derived CNTs and CNFs are demonstrated as high performance energy storage materials in both lithium-ion and sodium-ion batteries. Owing to synthetic control of sp3 content in the synthesized nanostructures, optimized storage capacities are measured over 370 mAh g–1 (lithium) and 130 mAh g–1 (sodium) with no capacity fade under durability tests up to 200 and 600 cycles, respectively. This work demonstrates that ambient CO2, considered as an environmental pollutant, can be attributed economic value in grid-scale and portable energy storage systems with STEP scale-up practicality in the context of combined cycle natural gas electric power generation.

Electrochemical synthesis of ammonia directly from N2 and water over iron-based catalysts supported on activated carbon

A new green methodology for the CO2-free synthesis of ammonia from air and water is presented. The conventional production of H2 utilizes fossil fuels and causes a massive greenhouse gas release, making ammonia production one of the most energy intensive and highest CO2 emitting manufacturing processes. In 2014 we introduced an alternative method for efficient ammonia synthesis that utilizes water (along with N2) instead of H2 based on electrolysis of nano-structured catalyst suspensions of Fe2O3 in low temperature aqueous or higher temperature molten hydroxide electrolytes. Here, this is replaced with a solid Fe2O3 catalyst confined to activated charcoal opening pathways to improve the rate and efficiency of ammonia production. Cyclovoltammetric studies show that Fe2O3/AC catalysts can inhibit competing hydrogen reduction and enhance reduction of iron. This iron-based catalyst supported on activated carbon (Fe2O3/AC) was prepared for use as an electrocatalyst for the electrochemical synthesis of ammonia in molten hydroxide (NaOH–KOH) directly from wet N2 at atmospheric pressure. XRD analysis shows that the catalyst exhibits a Fe2O3 structure. At 250 °C, a voltage of 1.55 V with a current density of 49 mA cm−2 yielded the highest rate of ammonia formation, 8.27 × 10−9 mol (s cm2)−1. The highest coulombic efficiency for the 3e− per ammonia formation, 13.7%, was achieved at 1.15 V with a lower average current density of 11 mA cm−2. This is a promising simple technology for the sustainable synthesis of ammonia in the future.

Data on SEM, TEM and Raman Spectra of doped, and wool carbon nanotubes made directly from CO2 by molten electrolysis

This SEM, TEM and Raman Spectra and economic calculations data provides a benchmark for carbon nanotubes synthesized via molten electrolyte via the carbon dioxide to carbon nanotube (C2CNT) process useful for comparison to other data on longer length C2CNT wools; specifically: (I) C2CNT electrosynthesis with bare (uncoated) cathodes and without pre-electrolysis low current activation. (II) C2CNT Intermediate length CNTs with intermediate integrated electrolysis charge transfer. (III) C2CNT Admixing of sulfur, nitrogen and phosphorous (in addition to boron) to carbon nanotubes, and (IV) Scalability of the C2CNT process. This data presented in this article are related to the research article entitled “Carbon Nanotube Wools Made Directly from CO2 by Molten Electrolysis: Value Driven Pathways to Carbon Dioxide Greenhouse Gas Mitigation” (Johnson et al., 2017) [1].

Carbon nanotube wools made directly from CO2 by molten electrolysis: Value driven pathways to carbon dioxide greenhouse gas mitigation

A climate mitigation comprehensive solution is presented through the first high yield, low energy synthesis of macroscopic length carbon nanotubes (CNT) wool from CO2 by molten carbonate electrolysis, suitable for weaving into carbon composites and textiles. Growing CO2 concentrations, the concurrent climate change and species extinction can be addressed if CO2 becomes a sought resource rather than a greenhouse pollutant. Inexpensive carbon composites formed from carbon wool as a lighter metal, textiles and cement replacement comprise a major market sink to compactly store transformed anthropogenic CO2. 100x-longer CNTs grow on Monel versus steel. Monel, electrolyte equilibration, and a mixed metal nucleation facilitate the synthesis. CO2, the sole reactant in this transformation, is directly extractable from dilute (atmospheric) or concentrated sources, and is cost constrained only by the (low) cost of electricity. Todays

One-pot synthesis of nanostructured carbon materials from carbon dioxide via electrolysis in molten carbonate salts

100K per ton CNT valuation incentivizes CO2 removal.