Fundamental studies of ruthenium species supported on boron nitride nanotubes: metal loading and pretreatment effects on CO oxidation

Multiwalled boron nitride nanotube (BNNT), as a catalyst support, has become one of the promising materials due to its high oxidation resistance and thermal stability. In this work, ruthenium (Ru) supported on BNNT catalysts with different metal loadings and treatment conditions was investigated for CO oxidation as a model reaction. To understand the physicochemical properties of the prepared samples, a suite of techniques, including FTIR, UV-Raman, SEM, TEM, and XPS, was utilized. The results showed that the RuO_x species were located on both the interior and the exterior surfaces of the BNNT, and an increase in metal loading led to increased active sites. 1 wt% RuO_x/BNNT (oxidized) exhibited better catalytic activity than 1 wt% Ru/BNNT (reduced), indicating that treatment conditions significantly affect the catalytic properties. Reaction conditions, such as GHSV and the O₂/CO ratio, were varied to further investigate the external mass transfer limitations and reaction mechanism of the 1 wt% RuO_x/BNNT catalyst. The peculiar tubular morphology of the BNNT resulted in negligible external mass transfer limitation, and the catalyst might primarily follow the Eley-Rideal (ER) mechanism over the Langmuir-Hinshelwood (LH) mechanism.