Thermocatalytic Upcycling of Plastic into Ni-Encapsulated Carbon Nanotube Electrocatalysts for Green Hydrogen Production.

Abstract

The escalating accumulation of plastic waste poses a critical environmental challenge. Here, we report a controllable solvent- and H₂-free disassembly (CSHFD) strategy using Ni-decorated nanoparticles (NPs) on ordered microporous carbon (Ni-OMC) for plastic upcycling. The optimized Ni₂₀-OMC (20 wt % Ni NPs) achieved an H₂ yield of 55.26 mmol g^-1 plastic with an H₂ proportion of 86.86 vol %, attributed to the abundant metallic Ni active sites on the carbon skeleton that facilitated C-C and C-H bond cleavage. Notably, the in situ formation of plastic-derived carbon nanotubes (CNTs) encapsulating metallic Ni NPs on microporous carbon (Ni-CNTs-OMC) as functionalized nanocomposites bridged thermocatalysis and electrocatalysis. Remarkably, the Ni₂₀-CNTs-OMC (CNTs anchored on Ni₂₀-OMC) exhibited superior hydrogen evolution reaction (HER) performance in alkaline electrolyte, requiring an overpotential of only 215 mV at 10 mA cm^-2 and retaining robust stability over 15,000 cycles. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) revealed strengthened hydrogen-bond networks and optimized *H adsorption, accelerating HER kinetics. Density functional theory (DFT) calculations further indicated that the Ni-encapsulated CNT structure modulated CNT electron distribution and lowered the Gibbs free energies of HER intermediates. Simply put, this work offers a sustainable and integrated approach to transform plastic waste into high-performance electrocatalysts and green H₂, establishing a paradigm for bridging thermocatalysis and electrocatalysis toward a circular carbon economy.