Controlled Transition Metal Nucleated Growth of Carbon Nanotubes by Molten Electrolysis of CO$_2$

TL;DR

This paper presents a novel electrochemical method using molten carbonate to convert atmospheric CO$_2$ into carbon nanotubes, offering a potentially cheaper and more environmentally friendly alternative to traditional CVD techniques.

Contribution

It introduces a controlled electrolysis process in molten lithium carbonate to synthesize CNTs directly from CO$_2$, with detailed analysis of morphologies and growth mechanisms.

Findings

Successful synthesis of various CNT morphologies via electrolysis

Detailed characterization of CNT structures and growth mechanisms

Potential for low-cost, low-emission CNT production from atmospheric CO$_2$

Abstract

The electrolysis of CO$_2$ in molten carbonate has been introduced as an alternative mechanism to synthesize carbon nanomaterials inexpensively at high yield. Until recently, CO$_2$ was thought to be unreactive, making its removal a challenge. CO$_2$ is the main cause of anthropogenic global warming and its utilization and transformation into a stable, valuable material provides an incentivized pathway to mitigate climate change. This study focuses on controlled electrochemical conditions in molten lithium carbonate to split CO$_2$ absorbed from the atmosphere into into carbon nanotubes, and into various macroscopic assemblies of CNTs,, which may be useful for nano-filtration. Different CNTs, morphologies were prepared electrochemically by variation of the anode and cathode composition and architecture, electrolyte composition pre-electrolysis processing, and the variation of current application and current density. Individual CNT morphologies structures and the CNT molten carbonate growth mechanism are explored by SEM, TEM, HAADF EDX, XRD and Raman. The principle commercial technology for CNT production had been chemical vapor deposition, which is an order of magnitude more expensive, generally requires metallo-organics, rather than CO$_2$ as reactants, and can be highly energy and CO$_2$ emission intensive (carries a high carbon positive, rather than negative, footprint).