(111h) Tuning Nickel-Based Catalyst for Hydrogen and Carbon Nanofibers

Hydrogen is one of the most essential chemical building blocks to our energy infrastructure, with downstream applications in oil refining as well as production of ammonia, the key component in fertilizer. Today, nearly all hydrogen is produced commercially via steam methane reforming. For every kilogram of hydrogen produced, there are roughly 9 kilograms of CO₂ released to the atmosphere. With an estimated global hydrogen production rate of 75 MMTA, over 675 MMTA of CO₂ are emitted via this process. A profitable alternative to produce hydrogen while circumventing greenhouse gas is needed. A catalytic methane pyrolysis process to produce hydrogen and carbon nanofibers (CNFs) is a financially promising alternative to steam methane reforming.

The economic viability of methane pyrolysis largely relies on the carbon co-product value. In this research, CNFs are produced via a vapor-deposited nickel catalyst on a silica fume support. CNFs are the carbon product of focus for this reaction due to their advantageous properties, specifically when incorporated into concrete mix designs. To explore viable applications of the CNFs in concrete while avoiding costly catalyst/carbon separation, the catalyst, support, and CNFs combine as one product to improve the strength and durability of concrete. In partnership with the Hubler group in the department of Civil Engineering, we are investigating the CNF/catalyst product to reduce cracking and improve the durability of high purity concrete.

In this work, an experimental design was performed to determine the catalyst preparation parameters that most influence nickel particle size, particle size distribution, and morphology. Nickel particles were characterized via scanning-transmission electron microscopy (STEM), small angle x-ray scattering (SAXS), and x-ray diffraction (XRD). Subsequently, methane pyrolysis was carried out in a fluidized bed reactor over the prepared Ni/SiO₂ catalyst. Hydrogen yield, carbon yield, and CNF morphology were investigated and correlated to the starting catalyst properties