Reconstruction of supported nanocatalysts often occurs in gas-solid reactions and significantly affects the catalytic performance,yet it is much less explored in liquid-phase environment.Herein,we find that highly-dis...Reconstruction of supported nanocatalysts often occurs in gas-solid reactions and significantly affects the catalytic performance,yet it is much less explored in liquid-phase environment.Herein,we find that highly-dispersed Ag nanocatalysts,i.e.,AgOx clusters,supported on alumina,silica,and titania,can aggregate into larger Ag or Ag2O particles after immersing in liquid-phase media at room temperature.The spontaneous aggregation of AgOx clusters in liquid water is attributed to liquid-phase Ostwald ripening through dissolution of AgOx clusters into water and subsequent redeposition to form Ag2O particles.The immersion into organic solvents such as ethanol leads to reduction of AgOx clusters and further growth into Ag particles.This work reveals that liquid-phase reaction media can induce substantial structural evolution of supported nanostructured catalysts,which should be carefully considered in liquid-solid interface catalytic reactions such as electrocatalysis,environmental catalysis,and organic synthesis in liquid phase.展开更多
Water is often involved in many catalytic processes,which can strongly affect structural evolution of catalysts during pretreatments and catalytic reactions.In this work,we demonstrate a promotional effect of H_(2)O o...Water is often involved in many catalytic processes,which can strongly affect structural evolution of catalysts during pretreatments and catalytic reactions.In this work,we demonstrate a promotional effect of H_(2)O on both oxidative dispersion and spontaneous aggregation of Ag nanocatalysts supported on alumina.Ag nanoparticles supported onγ-Al_(2)O_(3) and Ag nanowires on Al_(2)O_(3)(0001)can be dispersed into nanoclusters via annealing in O_(2)above 300℃,which is accelerated by introduction of H_(2)O into the oxidative atmosphere.Furthermore,the formed highly dispersed Ag nanoclusters are subject to spontaneous aggregation in humid atmosphere at room temperature.Ex situ and in situ characterizations in both powder and model catalysts suggest that formation of abundant surface hydroxyls and/or water adlayer on the Al_(2)O_(3) surface in the H_(2)O-containing atmosphere facilitates the surface migration of Ag species,thus promoting both dispersion and aggregation processes.The aggregation of the supported Ag nanostructures induced by the humid oxidative atmosphere enhances CO oxidation but inhibits selective catalytic reduction of NO with C_(3)H_(6).This work illustrates the critical role of H_(2)O in structure and catalytic performance of metal nanocatalysts,which can be widely present in heterogeneous catalysis.展开更多
基金National Key Research and Development Program of China(Nos.2021YFA1502800,2022YFA1504800,and 2022YFA1504500)the National Natural Science Foundation of China(Nos.21825203,22288201,22332006,and 22321002)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0600300)the Fundamental Research Funds for the Central Universities(No.20720220009)Photon Science Center for Carbon Neutrality。
文摘Reconstruction of supported nanocatalysts often occurs in gas-solid reactions and significantly affects the catalytic performance,yet it is much less explored in liquid-phase environment.Herein,we find that highly-dispersed Ag nanocatalysts,i.e.,AgOx clusters,supported on alumina,silica,and titania,can aggregate into larger Ag or Ag2O particles after immersing in liquid-phase media at room temperature.The spontaneous aggregation of AgOx clusters in liquid water is attributed to liquid-phase Ostwald ripening through dissolution of AgOx clusters into water and subsequent redeposition to form Ag2O particles.The immersion into organic solvents such as ethanol leads to reduction of AgOx clusters and further growth into Ag particles.This work reveals that liquid-phase reaction media can induce substantial structural evolution of supported nanostructured catalysts,which should be carefully considered in liquid-solid interface catalytic reactions such as electrocatalysis,environmental catalysis,and organic synthesis in liquid phase.
基金This work was financially supported by the National Key R&D Program of China(No.2021YFA1502800)the National Natural Science Foundation of China(Nos.91945302,21825203,and 22288201)Photon Science Center for Carbon Neutrality.
文摘Water is often involved in many catalytic processes,which can strongly affect structural evolution of catalysts during pretreatments and catalytic reactions.In this work,we demonstrate a promotional effect of H_(2)O on both oxidative dispersion and spontaneous aggregation of Ag nanocatalysts supported on alumina.Ag nanoparticles supported onγ-Al_(2)O_(3) and Ag nanowires on Al_(2)O_(3)(0001)can be dispersed into nanoclusters via annealing in O_(2)above 300℃,which is accelerated by introduction of H_(2)O into the oxidative atmosphere.Furthermore,the formed highly dispersed Ag nanoclusters are subject to spontaneous aggregation in humid atmosphere at room temperature.Ex situ and in situ characterizations in both powder and model catalysts suggest that formation of abundant surface hydroxyls and/or water adlayer on the Al_(2)O_(3) surface in the H_(2)O-containing atmosphere facilitates the surface migration of Ag species,thus promoting both dispersion and aggregation processes.The aggregation of the supported Ag nanostructures induced by the humid oxidative atmosphere enhances CO oxidation but inhibits selective catalytic reduction of NO with C_(3)H_(6).This work illustrates the critical role of H_(2)O in structure and catalytic performance of metal nanocatalysts,which can be widely present in heterogeneous catalysis.
