Synthesis of CeO2 Supported Period 4 Transition Metal Catalysts Via One Pot Chemical Vapor Deposition (OP-CVD) Method

Platinum group metals (PGMs) are recognized to be the most efficient, yet expensive surface species for heterogeneous catalysts. To mitigate this expense, extensive research is being done on alternative cost-effective transition metals as surface species for these catalysts. Period 4 transition metals such as Cr, Mn, Fe, Co, Ni, and Cu have been studied to determine which one(s) produces the most desirable characteristics for a catalyst, such as high dispersion, small particle size, and high reactivity. Cerium oxide (CeO2) was used as the support material because it’s been proven effective due to its lattice configuration, which enables it to perform redox easily (Ce3+ ↔ Ce4+) and maintain a high oxygen capacity. Various synthesis methods to produce CeO2 supported catalysts, including dry or wet impregnation, precipitation, and spray pyrolysis, have exhibited limitations related to low surface species dispersion and metal agglomerations on the support material. In this study, we developed and applied a new synthesis method known as one pot chemical vapor deposition (OP-CVD) to combat these drawbacks. OP-CVD uses gas-solid interactions to produce MOx/CeO2 catalysts, where M is a period 4 transition metal, aiming to achieve full dispersion of these surface species onto the CeO2 support. These synthesized catalysts were then applied to CO oxidation as a model reaction. To validate the feasibility of OP-CVD in achieving high surface species dispersion and gain insights into the molecular structure, we employed multiple characterization techniques including thermogravimetric analysis (TGA), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, inductively coupled plasma optical emission spectrometry (ICP-OES), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The characterization results confirm that surface transition metal oxides were effectively dispersed on the CeO2 support. The simplicity of the OP-CVD method holds great potential for synthesizing supported metal oxide (or metal) catalysts.