Carbon Dioxide Conversion To Advanced Carbon Nanotubes

Abstract The conversion of CO2 into valuable substances is a topic of great interest for decarbonization. Among them, the CO2 conversion to advanced materials such as carbon nanotubes (CNTs) has emerged as promising CO2 utilization. In this work, we have successfully developed catalysts and process to convert CO2 to CNTs. We developed catalysts by loading active transition metals on to hierarchical zeolite for CNT synthesis using CO2 as raw material. The synthesis of CNTs from CO2 over the developed catalysts was carried out via a chemical vapor deposition (CVD) process. The quantity and quality of the resulting carbon nanotubes were determined using thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The synthesized CNTs were also evaluated for their current response using cyclic voltammetry (V vs. Ag/AgCl) method. By optimizing metal type, metal loading, zeolite topologies and pore structures (hierarchically porous or conventionally microporous), we successfully converted CO2 to CNTs over the metal-loaded hierarchical zeolite catalysts. The CNTs produced using the 25wt.% Fe on hierarchical FAU zeolite provided the most promising result with a high CNTs yield of 15.4%, an average CNTs diameter size of 23.1 nm, and ID/IG ratio of 0.56 indicating high quality CNTs. The synthesized CNTs were tested and exhibited higher current response compared to commercial CNTs. This enhanced performance highlights the significant contribution of the small diameter and superior quality of our synthesized pure CNT. Transition metals play a crucial role as catalysts in the decomposition of CO2 during the CNTs synthesis. Moreover, well-distribution of metal nanoparticles on the hierarchical zeolite contributes to enhanced catalytic activity, consequently resulting in more favorable CNTs synthesis outcomes. This work demonstrates conversion of CO2 towards highly conductive CNTs-based materials, which have many potential applications including energy storages, sensors, electronic circuits, etc.