H$_2$ [Pt(C$_2$O$_4$)$_2$] as a Tailor‐made Halide‐free Precursor for the Preparation of Diesel Oxidation Catalysts: Nanoparticles Formation, Thermal Stability and Catalytic Performance

Abstract

The aim of this study was to investigate a tailor-made metal precursor and its chemical properties to tune the properties of supported metal nanoparticles (NPs) and their catalytic performance when used as Diesel Oxidation Catalyst (DOC). The formation of extremely small Pt NPs from a new halide-free Pt complex was investigated, namely bis(oxalato)platinate, H$_2$ [Pt(C$_2$O$_4$)$_2$]. The size evolution of the supported NPs, from the formation upon the Pt precursor decomposition on γ-alumina to the sintering of the NPs at high temperatures, was followed by thermogravimetric analysis coupled with mass spectrometry (TG-MS) and differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A correlation between the NPs’ size of the catalyst and the performance for the CO, C$_3$H$_6$, C$_3$H$_8$ and NO oxidation reactions pointed out a retained activity during test cycles, showing low sensitivity to the test conditions applied (i. e., temperature and gas composition). The overall catalytic performance was better in the fresh catalysts compared to the reference catalyst prepared from platinum nitrate, Pt(NO$_3$)$_4$. In particular, the different dispersion of the Pt NPs over the support obtained from the two precursors was identified as the reason for the different catalytic performance, retaining small NPs size after the tests cycles