In Situ Generation of the Surface Oxygen Vacancies in a Copper–Ceria Catalyst for the Water–Gas Shift Reaction

Abstract

The dissociation of H2O is a crucial aspect for the water–gas shift reaction, which often occurs on the vacancies of a reducible oxide support. However, the vacancies sometimes run off, thus inhibiting H2O dissociation. After high-temperature treatment, the ceria supports were lacking vacancies because of sintering. Unexpectedly, the in situ generation of surface oxygen vacancies was observed, ensuring the efficient dissociation of H2O. Due to the surface reconstruction of ceria nanorods, the copper species sustained were highly dispersed on the sintered support, on which CO was adsorbed efficiently to react with hydroxyls from H2O dissociation. In contrast, no surface reconstruction occurred in ceria nanoparticles, leading to the sintering of copper species. The sintered copper species were averse to adsorb CO, so the copper–ceria nanoparticle catalyst had poor reactivity even when surface oxygen vacancies could be generated in situ.

Approaching C1 Reaction Mechanisms Using Combined Operando and Transient Analysis: A Case Study on Cu/CeO2 Catalysts during the LT-Water–Gas Shift Reaction

“…Previous literature studies on Cu/CeO 2 catalysts have highlighted the importance of the copper oxidation state, ,,, which depends on both the gas-phase environment and the loading. ,, On the one hand, the interaction of metallic copper with oxygen vacancies (O vac ) was reported to enhance the reactivity, while on the other, copper was shown to have an oxidation state of +1 at the interface and to participate in the reaction, as supported by other studies, demonstrating the stability of oxidized copper under reductive conditions . In addition, a strong dependence of the state of copper on the gas phase at 180 °C was observed for 20 wt % Cu/CeO 2 , that is, mainly Cu 0 was detected during CO exposure and Cu + in the subsequent exposure to an inert gas .…”

“…36,42,43 On the one hand, the interaction of metallic copper with oxygen vacancies (O vac ) was reported to enhance the reactivity, 26 while on the other, copper was shown to have an oxidation state of +1 at the interface and to participate in the reaction, 44 as supported by other studies, demonstrating the stability of oxidized copper under reductive conditions. 45 In addition, a strong dependence of the state of copper on the gas phase at 180 °C was observed for 20 wt % Cu/CeO 2 , that is, mainly Cu 0 was detected during CO exposure and Cu + in the subsequent exposure to an inert gas. 42 At low loadings, for example, 1 wt % Cu/CeO 2 , the catalyst behaves differently, as rather Cu + is observed under a CO atmosphere, which is then further oxidized to Cu 2+ on switching to He, 43 indicative of electronic metal−support interactions.…”

Solution Plasma Processing Single‐Atom Au1 on CeO2 Nanosheet for Low Temperature Photo‐Enhanced Mars–van Krevelen CO Oxidation

“…The Mars-van Krevelen (MvK) process is broadly acknowledged in catalytic oxidation over metal oxides, [1] being essential to design catalysts for multiple applications such as CO oxidation, [2] water gas shifted reaction (WGS), [3] abatement of volatile organic compounds, [4] etc. Activation of lattice oxygen is the key step during the MvK process [5] and closely related to the onset temperature of catalytic oxidation.…”

Heterostructured Ceria–Titania-Supported Platinum Catalysts for the Water Gas Shift Reaction

“…Supported metal catalysts have been widely applied to many catalytic processes due to their remarkable reactivity. − The nature of the metal and support will affect the metal–support interaction and further influence the catalytic performance . Over the years, researchers have studied plenty of single-oxide support catalysts such as CeO 2 -, ,, SiO 2 -, , TiO 2 -, , and Al 2 O 3 - , supported active metals.…”

“…In recent years, the water gas shift (WGS) reaction has attracted considerable attention because it provides an effective approach for the preparation and purification of hydrogen ,, as a process to remove trace amounts of CO in proton-exchange membrane fuel cells. ,, Many catalysts such as Au, ,,, Pt, ,, or Cu ,,, supported on oxide supports including CeO 2 , ,, TiO 2 , − Al 2 O 3 , , and SiO 2 , have been widely studied due to their excellent catalytic activity for the WGS reaction. It was reported that a very small amount of Pt on the oxide support showed more superior catalytic activity than Cu and Au .…”