Temperature-dependent synthesis of multi-walled carbon nanotubes and hydrogen from plastic waste over A-site-deficient perovskite La0.8Ni1-xCoxO3-δ

Abstract

Thermochemical conversion of plastic wastes into carbon nanotubes (CNTs) and hydrogen is a promising management option to eliminate their hazardous effect. The yields and morphologies of CNTs strongly depend on the catalyst design and reaction conditions. To boost the efficiency, tuning of bimetallic nanoparticles as catalyst is an effective approach. For that reason, A-site-deficient perovskite La_0·8Ni_1-xCo_xO_3-δ (LN_1-xC_x, x = 0.15, 0.5, 0.85) was developed and used as a catalyst precursor to achieve in situ formation of bimetallic Ni-Co nanoparticles. At an optimized Ni-to-Co ratio, the LN_0.5C_0.5 exhibited the highest yields of multi-walled CNTs, namely 840 and 853 mg/g_catalyst from high density polyethylene and polypropylene, respectively. This could be attributed to the higher catalytic capability of LN_0.5C_0.5 catalyst for the decomposition of hydrocarbons into hydrogen and carbon. In both cases, multi-walled CNTs had regular shapes when the reaction temperature was 700 °C. At higher reaction temperatures, the morphological changes of carbon products were observed from multi-walled CNTs to carbon nano-onions. The Raman spectra showed that compared with the commercial multi-walled CNTs, the as-prepared multi-walled CNTs had a lower degree of defects.

Keywords: A-site-deficient perovskite; Bimetallic Ni–Co nanoparticles; Carbon nano-onions; Multi-walled carbon nanotubes; Plastics upcycling.