Upgrading polyurethane using pyrolytic methods: exploring the liquid and solid fractions towards fuels and electrocatalyst production

Pursuing the circular economy, herein, valorization of polyurethane (PU) foams has commenced by virtue of atmosphere-controlled pyrolysis. Nitrogen-rich carbonaceous char and the oil samples were acquired at pyrolysis temperatures of 400 °C, 600 °C, and 800 °C. The solid char was then functionalized with 10 wt% iron phthalocyanine (FePc) to develop Fe-Nx-C electrocatalysts for oxygen reduction reaction (ORR), which is a bottleneck in the commercial realization of fuel cells. Half-cell ORR measurements in alkaline media confirmed the electrocatalyst efficacy based on the char obtained at 800 °C ((C800)Fe). To improve the reaction kinetics, Ketjenblack (KJB) electroconductive carbon was added in different proportions, 25, 50, and 75% in C800, prior to FePc functionalization. Even the smallest addition of KJB led to a great improvement. The sample (75C800_25KJB)Fe demonstrated an onset potential of 932 mV (vs RHE), along with the direct 4-electron ORR, showing stability over 2000 cycles. Moreover, the pyrolysis oil samples were thoroughly analyzed: at 400–600 °C, aliphatic/polyether oligomers predominated, suitable for polyol recovery/lubricants; at 800 °C, nitrogen-aromatic structures emerged for chemical/combustible valorization, showing a decrease in number–average molecular weight with temperature. Eventually, through a Cost-Benefit Analysis, an economic evaluation was conducted, highlighting a positive socio-economic potential for the proposed upcycling of waste PU.