Jiawen Ren

One-Pot Synthesis of Carbon Nanofibers from CO2

Carbon nanofibers, CNFs, due to their superior strength, conductivity, flexibility, and durability have great potential as a material resource but still have limited use due to the cost intensive complexities of their synthesis. Herein, we report the high-yield and scalable electrolytic conversion of atmospheric CO2 dissolved in molten carbonates into CNFs. It is demonstrated that the conversion of CO2 → CCNF + O2 can be driven by efficient solar, as well as conventional, energy at inexpensive steel or nickel electrodes. The structure is tuned by controlling the electrolysis conditions, such as the addition of trace transition metals to act as CNF nucleation sites, the addition of zinc as an initiator and the control of current density. A less expensive source of CNFs will facilitate its adoption as a societal resource, and using carbon dioxide as a reactant to generate a value added product such as CNFs provides impetus to consume this greenhouse gas to mitigate climate change.

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.

Tracking airborne CO2 mitigation and low cost transformation into valuable carbon nanotubes

Primary evidence of the direct uptake of atmospheric CO2 and direct transformation into carbon nanotubes, CNTs, is demonstrated through isotopic labeling, and provides a new high yield route to mitigate this greenhouse gas. CO2 is converted directly to CNTs and does not require pre-concentration of the airbone CO2. This C2CNT (CO2 to carbon nanotube) synthesis transforms CO2-gas dissolved in a 750 °C molten Li2CO3, by electrolysis, into O2-gas at a nickel electrode, and at a steel cathode into CNTs or carbon or nanofibers, CNFs. CNTs are synthesized at a 100-fold price reduction compared to conventional chemical vapour deposition, CVD, synthesis. The low cost conversion to a stable, value-added commodity incentivizes CO2 removal to mitigate climate change. The synthesis allows morphology control at the liquid/solid interface that is not available through conventional CVD synthesis at the gas/solid interface. Natural abundance 12CO2 forms hollow CNTs, while equivalent synthetic conditions with heavier 13CO2 favours closed core CNFs, as characterized by Raman, SEM and TEM. Production ease is demonstrated by the first synthesis of a pure 13C multiwalled carbon nanofiber.

How does an amalgamated Ni cathode affect carbon nanotube growth? A density functional theory study

This is a Density Functional Theory (DFT) study on the influence of an alloying mixture of Ni–Zn catalysts on carbon nanotube, CNT, growth. The study is inspired by the one pot synthesis of carbon nanofibers during the electrolysis of Li2CO3. Unlike CVD, CNT growth initiates at the liquid/solid, rather than gas/solid interface in the above process. The electrodes are an amalgamated Zn cathode and with a pure Ni crucible as the anode, and both zinc and nickel (or other transition metals) are required for high yield production. The use of transition metals as the catalyst for CNT, CVD growth is well known. However, in this study we show how a mixture of the Zn–Ni alloy can act as the catalyst for the effective CNT growth. Ni and Zn are taken as an example of first row transition metals with a partially empty and completely filled d orbital respectively. The study shows that the π–d bonding between the nanotube and the metal results in strong bond formation at the interface of the nanotube growth. The study remains valid for other such metal alloys with partially and completely filled d orbitals.

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.