Catalyst discovery through megalibraries of nanomaterials.

The nanomaterial landscape is so vast that a high-throughput combinatorial approach is required to understand structure-function relationships. To address this challenge, an approach for the synthesis and screening of megalibraries of unique nanoscale features (>10,000,000) with tailorable location, size, and composition has been developed. Polymer pen lithography, a parallel lithographic technique, is combined with an ink spray-coating method to create pen arrays, where each pen has a different but deliberately chosen quantity and composition of ink. With this technique, gradients of Au-Cu bimetallic nanoparticles have been synthesized and then screened for activity by in situ Raman spectroscopy with respect to single-walled carbon nanotube (SWNT) growth. Au3Cu, a composition not previously known to catalyze SWNT growth, has been identified as the most active composition.

Co-, Ni-, and Cu-Doped Fe-Based Catalysts for the Microwave-Assisted Catalytic Pyrolysis of Polyethylene.

Environmental issues caused by waste polyethylene are becoming increasingly severe. Among potential treatment processes, microwave-assisted catalytic pyrolysis is promising for converting waste plastics into valuable products owing to its energy efficiency and environmental sustainability. Herein, a modified citric acid combustion method was used to prepare a series of metal oxide catalysts with loose porous structures. The prepared Fe-based catalysts doped with Co, Ni, or Cu were employed in the microwave-assisted catalytic pyrolysis of polyethylene. The bimetallic Co1Fe1Ox catalyst exhibited the best performance, yielding hydrogen at a rate of 60.7 mmol/gplastic. Further variation in the Co : Fe ratio revealed that the Co1Fe9Ox catalyst achieved the highest hydrogen production efficiency (63.64 mmol/gplastic). Similar oil-phase products were obtained over the various catalysts, as revealed by infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Furthermore, scanning electron microscopy (SEM) identified carbon nanotubes as the major solid product of pyrolysis, which were attached to the catalyst surface. Finally, a combination of thermogravimetric analysis, SEM, and energy-dispersive X-ray spectroscopy indicated that the reduction in catalytic activity following recycling was caused by the accumulation of carbonaceous products on the catalyst surface. Overall, Co1Fe9Ox catalysts were favorable for obtaining H2 and carbon nanotubes by the microwave-assisted pyrolysis of polyethylene.