CO oxidation on supported platinum group metal (PGM) based nanoalloys

Abstract

The oxidation of carbon monoxide is widely investigated for realistic and potential uses in energy production and environmental processes. As a probe reaction to the surface properties, it gives an insight into the relationship between the structure of active phase and catalytic performance. Noble metals alloyed with certain transition metals in the form of a nanoalloy exhibit enhanced catalytic activity for various reactions, especially when simultaneous activation of oxygen and CO is involved. This article highlights some of these insights into nanoalloy catalysts in which platinum group metal (PGM) is alloyed with a second and/or third transition metal (M/M′=Co, Fe, V, Ni, Ir, etc.), for catalytic oxidation of carbon monoxide in a gas phase. Recent studies have provided important insights into how the atomic-scale structures of the nanoalloy catalysts operate synergistically in activating oxygen and maneuvering surface oxygenated species. The exploration of atomic-scale chemical/structural ordering and coordination in correlation with the catalytic oxidation properties based on findings from ex-and in-situ synchrotron X-ray techniques is emphasized; for example, high-energy X-ray diffraction coupled to atomic-pair distribution function and X-ray absorption fine-structure spectroscopic analysis. The understanding of the detailed active sites of the nanoalloys has significant implications for the design of low-cost, active, and durable catalysts for sustainable energy production and environmental processes. nanoalloy catalysts, supported noble metal, carbon monoxide oxidation, synchrotron X-ray

Tiny Species with Big Impact: High Activity of Cu Single Atoms on CeO2–TiO2 Deciphered by Operando Spectroscopy

“…With an in-depth investigation of the heterogeneous catalytic oxidation of CO, , one can gain fundamental new insights into the performance of catalysts and even make progress on important technical applications such as preferential oxidation of CO (PROX), − air purification, exhaust-gas emission treatment, − proton-exchange membrane fuel cells, , CO sensors, and CO 2 lasers . Noble metals such as Pt, Rh, Pd, and Au, either nonsupported or supported on ceria, zirconia, titania, and alumina, are typical catalysts for this reaction. − CeO 2 is widely employed due to the highly active and reversible Ce 4+ /Ce 3+ redox shuttle and its unique ability to store and release oxygen. − Moreover, the high reducibility of CeO 2 and its tendency to form surface defects, in particular the O-vacancy defects, are known to stabilize highly dispersed metal species against sintering during reaction. − In CO oxidation, ceria is supposed to activate and supply oxygen from the lattice across the metal/ceria interface to react with CO adsorbed on the nearby metal species. ,, Besides, small CeO 2 particles alone can directly oxidize CO, although at higher temperatures, which may be another reason for the enhanced activity associated with ceria catalysts . The combination of noble metals, such as Pd and Pt with CeO 2 is desirable for several applications.…”

Applications of Rhodium and Ruthenium Catalysts for CO Oxidation: an Overview

“…The reaction mixture has an excess O 2 , close to the catalyst will be decreased in CO, and the surface will be exposed to an oxidizing atmosphere of O 2 and CO. The reaction of gasphase CO with oxide films was faster than the reabsorbed O on the metallic surfaces (Cai et al, 2015). The catalytic CO oxidation over Ru has been studied because of its irregular behavior compared with other transition metals.…”

Bimetallic Synergy on Iridium–Gold Catalysts for the CO Oxidation Reaction

“…Other applications of COOR are elimination of CO in closed air, vehicle emission control, and catalytic surface cleaning. − Commercially available CO oxidation catalysts fall into three categories: noble metal catalysts, transition metal catalysts, and mixed metal oxide catalysts. The COOR on pure metals such as Pt, Ir, Rh, and Pd has long been investigated, and it is considered a model reaction in heterogeneous catalysis. − The addition of noble metals into catalysts by a coprecipitation method has frequently been considered for low-temperature CO oxidation. For the vast majority of surface catalytic reactions, it has been accepted that the Langmuir–Hinshelwood mechanism (L–H) is preferred. − For this mechanism, oxygen activation is key.…”