Hydrogen and Syngas Production from Catalytic Pyrolysis of Engineering Plastic PEEK with Ni(OH)2

Polyether ether ketone (PEEK) is a high-performance thermoplastic with considerable potential for H 2 and syngas productions via pyrolysis. However, its conventional non-catalytic pyrolysis suffers from high energy consumption and low H 2 and syngas yields. This study investigates the catalytic pyrolysis of PEEK using nickel hydroxide (Ni(OH) 2 ) to enhance the gas production efficiency. PEEK mixed with Ni(OH) 2 at different molar ratios (1:0–1:2) was pyrolyzed up to 1073 K under a nitrogen atmosphere. The H 2 yield increased with catalyst loading and reached a maximum of 25.9 mg/g at a PEEK: Ni(OH) 2 ratio of 1:0.5 (13.85 wt%), corresponding to a 264.3% increase compared with non-catalytic pyrolysis. The syngas yield also reached a maximum of 0.75 g/g under the same condition. Thermogravimetric analysis showed that the addition of Ni(OH) 2 significantly lowered the onset decomposition temperature of PEEK from 832 K to 532 K, and transformed its two-stage pyrolysis into a four-stage process with a 10.4% reduction in char residue. In-situ X-ray diffraction revealed that Ni(OH) 2 was progressively transformed into NiO and Ni during heating, indicating the formation of catalytically relevant Ni-containing phases within the pyrolysis temperature range. Scanning electron microscopy showed that the catalyst was distributed within the carbon matrix and altered the morphology of the pyrolysis residue. These observations provide qualitative evidence of morphological changes after catalytic pyrolysis. These findings demonstrate that the catalytic potential of Ni(OH) 2 in facilitating H 2 -rich syngas production from PEEK.