Fully Dispersed Rh Ensemble Catalyst To Enhance Low-Temperature Activity

Abstract

Minimizing the use of precious metal catalysts is important in many applications. Single-atom catalysts (SACs) have received much attention because all of the metal atoms can be used for surface reactions. However, SACs cannot catalyze some important reactions that require ensemble sites. Here, Rh catalysts were prepared by treating 2 wt % Rh/CeO hydrothermally at 750 °C for 25 h. Nearly 100% dispersion was obtained, but the surface Rh atoms were not isolated (denoted as ENS). They catalyzed the oxidation of CH or CH at low temperatures, but these oxidations did not occur on the Rh SAC. When the simultaneous oxidation of CO, CH, and CH was performed, the T (temperature at conversion 20%) for CO oxidation increased significantly from 40 °C for sole CO oxidation to 180 °C on SAC due to the competitive adsorption of hydrocarbons. However, T increased much less on ENS, from 60 to 100 °C. ENS exhibited superior activity for low-temperature oxidation. During hydrothermal treatment for 25 h, the Rh size initially increased from 2.3 to 6.7 nm then decreased to 0.9 nm. The surface hydroxyl groups formed on the catalyst surface help detach Rh atoms from Rh clusters, while preventing the reaggregation of dispersed Rh atoms into Rh clusters. This fully dispersed catalyst would have maximum atom-efficiency while catalyzing various surface reactions.

Design of Ceria Catalysts for Low‐Temperature CO Oxidation

“…Catalysts with high activity at low temperature include mostly precious metal catalysts (such as Pd, Pt, and Rh). [18][19][20] Despite the limited reserves and high price, precious metal catalysts exhibit very high activity, and is therefore, difficult to exclude them from various industries. For this reason, many researchers have developed catalysts with high catalytic activity by reducing the amount of precious metals or using inexpensive metals.…”

Single-atom site catalysts for environmental catalysis

“…As expected, over the last decade, SACs have made remarkable progress in catalytic elimination of pollutants, thereby possible for commercial use in environmental catalysis [54,56,58,64,[66][67][68]. As shown in Fig.…”

“…[57]; 2018, Rh1/CeO2 from Ref. [58], Fe-based single-atom alloy (SAA) from Ref. [59], and Fe1/CN from Ref.…”

Improving the Catalytic Activity of Carbon‐Supported Single Atom Catalysts by Polynary Metal or Heteroatom Doping

“…According to the different supports, SACs can be divided into non‐metal supports such as carbon‐based materials, [ 10 ] graphitic carbon nitride (g‐C 3 N 4 ), [ 11–13 ] hexagonal boron nitride (h‐BN), [ 14,15 ] phosphorus nitride, [ 16 ] and metal‐based supports such as Cu, [ 17 ] ZnO, [ 18 ] TiO 2 , [ 19 ] CeO 2 , [ 20,21 ] MgO, [ 22 ] CrO 2 , [ 6 ] MoS 2 , [ 23 ] Al 2 O 3 , [ 24 ] and Bi 3 O 4 Br. [ 25 ] Carbon‐supported SACs have achieved substantial progress in electrocatalysis due to the various advantages of carbon‐based materials such as high conductivity, high specific area, abundant carbon reservation, and various carbon derivatives, particularly graphene‐based materials.…”