Efficient hydrogen production and anti-coking via reforming of waste plastics by oxygen vacancy promoted plasma-catalysis

Hydrogen production from plastics contributes to the circular economy by enabling both waste valorisation and green energy generation. Integrated pyrolysis-plasma catalytic technology offers notable advantages in improving hydrogen production, but it still faces challenges such as catalyst coking and limited understanding of the reaction mechanisms. This study proposes a water vapor plasma-coupled oxygen vacancy-rich (O_v-rich) catalytic strategy to systematically investigate the improved hydrogen production from plastics over an anti-coking catalyst. The results show that the O_v-rich catalyst exhibits outstanding hydrogen production activity, strong synergistic effect, and universality in the non-thermal plasma catalytic (NTP-C) reforming reaction of mixed model compounds in plastic pyrolysis oil. Crucially, its practical effectiveness was successfully validated in the NTP-C reforming of polyethylene (PE)/polypropylene (PP) pyrolysis oils. Moreover, the O_v-rich catalysts significantly inhibited coking and maintained good stability for 1800 min in a multi-component mixed system. The mechanisms of hydrogen production and coking inhibition were revealed via Density Functional Theory (DFT) calculations, in situ plasma-coupled Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), and Optical Emission Spectroscopy (OES). A synergistic reaction pathway, coupling plasma gas-phase dissociation with catalytic surface reforming, was identified as a key mechanism for enhancing hydrogen yield in plasma-catalytic systems. The study offers valuable insights for advancing plasma-assisted hydrogen production technologies.