Microwave-assisted decomposition of waste plastic over Fe/FeAl2O4 to produce hydrogen and carbon nanotubes

This study experimentally investigated a novel approach for producing hydrogen and carbon nanotubes (CNTs) via high-density polyethylene (HDPE) cracking using Fe/FeAl2O4 under microwave radiation. We tested catalyst performance at different Fe-FeAl2O4 ratios and under different microwave powers and characterized. The catalysts were characterized by XRD, SEM/EDS, TEM, Raman, and TGA techniques. Additionally, we investigated the relationship between the structural properties of the catalysts and their activities. The results showed that Fe/FeAl2O4 catalyst can efficiently crack plastics into hydrogen and CNTs with the assistance of microwaves, and the catalyst with 30 wt% Fe loading exhibited optimal microwave absorption and catalytic activity. The hydrogen production is 47.03 mmol/gplastic (84.96 vol%). Furthermore, we evaluated the effect of microwaves on catalysts by simulating the electromagnetic field distribution, finding that the material was heated in the form of eddy current loss. CNTs follow different growth mechanisms on Fe and FeAl2O4 in the catalyst, namely the tip growth mechanism and the base growth mechanism, respectively.