Solar Conversion of Methane into Green Hydrogen and Multi-Walled Carbon Nanotubes as Sustainable Anode Material for Lithium-ion Batteries

Solar Conversion of Methane into Green Hydrogen and Multi-Walled Carbon Nanotubes as Sustainable Anode Material for Lithium-ion Batteries

Methane is the main component of natural gas and it is also a greenhouse gas that traps heat through the greenhouse effect. A methane molecule is 86X more potent than a CO2 molecule (for a period of 20 years). The warming potential of methane is 28-34 times that of CO2 with a 100-year global warming potential Measured over a 20-year period, that ratio grows to 84-86 times. Methane cracking is a methane decomposition process that breaks methane into hydrogen and different carbon nanostructures based on the catalyst used and the reaction conditions. The hydrogen from the process can be utilized as fuel for fuel cell cars, and the carbon nanostructures from the process can have numerous applications from pigments, paints, adsorbents, coatings, and composites for battery and supercapacitor energy storage and electronics. The challenge is that methane cracking is traditionally done through high thermal energy, which is energy-inefficient and unfeasible for commercial use.

Herein, we report carbon dioxide and carbon monoxide COx-free hydrogen (H2) and oxygen surface functionalized multiwalled carbon nanotubes (O-MWCNT) without any treatment as co-products via methane decomposition at ambient conditions. The highly selective simultaneous co-production of two industrially demanding compounds is efficient, self-sustaining, and environmentally benign compared to the traditional thermal method that requires very high temperature (600-1200 ?C) and lacks high H2 yield and MWCNT selectivity.

Our renewable solar approach features performance metrics with nearly 100% selectivity for H2 and solid O-MWCNT. The latter, can be separated, purified and used in further applications (e.g., energy storage devices, electronics, polymer composites, catalysis, nanotechnology, etc). We have demonstrated here the potential use of the O-MWCNT as a sustainable anode for Li-ion batteries. To improve the techno-economic of the process, the same MWCNT can be used as a support, offering a large surface area. A novel vertical reactor design was used to maximize the yield of MWCNT using light. Solar conversion of natural gas as greenhouse waste to solid MWCNT and H2, then to a COx-free electricity grid via a fuel cell, has potential economic and environmental benefits.

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