Heliyon (Nov 2024)
Hexagonal boron nitride fibers as ideal catalytic support to experimentally measure the distinct activity of Pt nanoparticles in CO2 hydrogenation
Abstract
Catalytic studies aim to design new catalysts to eliminate unwanted by-products and obtain 100 % selectivity for the preferred target product without losing activity. For this purpose, understanding the role of each component building up the catalyst is essential. However, determining the intrinsic catalytic activity of pure metals, especially precious metals in the CO2 hydrogenation reaction under ambient conditions is complex. This is because the catalyst supports used thus far always influence the catalytic process either directly or indirectly due to interface formation that modifies the electronic and morphological structure of the metals. Even SiO2, regarded as inert shows some activity owing to the hydroxyl groups on its surface. In this work, we propose chemically inert and defect-free hexagonal boron-nitride fibers (BNF) synthesized via a co-precipitation method with wide band gap and robust covalent bonds as an uncommon reference catalyst support to evaluate the catalytic activity of size-controlled Pt nanoparticles (4.7 ± 0.6 nm) in the hydrogenation of CO2. The fibers alone show no catalytic activity; however, Pt/BNF exhibited low but notable activity of 377 nmol/g at 400 °C and the catalyst can achieve nearly 100 % CO selectivity. X-ray photoelectron spectroscopy, transmission electron microscopy, and diffuse reflectance infrared Fourier transform spectroscopy measurements were used to indicate that hexagonal boron-nitride affects neither the metal nanoparticles nor the reaction itself; the measured catalytic activity stems from the activity of Pt deposites without the effect of the support, as they were alone. CO vibration spectroscopy studies suggest that due to the lack of substrate-metal interaction, Pt nanoparticles adopt an ideal spherical structure, resulting in several low coordination sites capable of CO2 conversion. Thus, BNF is proposed in the present article to be used as a reference catalyst support material. It can be efficiently used in investigations involving the proposed metal and reaction or under varying conditions with different metal nanoparticles and reaction systems.
