TY - JOUR

T1 - Exploring the mobility of Cu in bimetallic nanocrystals to promote atomic-scale transformations under a reactive gas environment

AU - Mathiesen, Jette K.

AU - Colding-Fagerholt, Sofie

AU - Jensen, Kim D.

AU - Pedersen, Jack K.

AU - Vosch, Tom

AU - Rossmeisl, Jan

AU - Helveg, Stig

AU - Jensen, Kirsten M. o.

PY - 2023

Y1 - 2023

N2 - Bimetallic nanocrystals (NCs) often show improved catalytic activities compared to their monometallic counterparts, but to optimize the performance it is crucial to understand how they behave under actual reaction conditions, i.e. in gas environments. Here, we use powder X-ray diffraction (PXRD), total scattering (TS) with pair distribution function (PDF) analysis and in situ high-resolution transmission electron microscopy (HR-TEM) to provide new insights into the atomic-scale behaviour of NC catalysts under a reactive gas environment. By investigating Au, Cu, Pd, PdCu, AuPd and AuCu NCs, we observe that the properties of bimetallic NCs differ significantly from their monometallic counterparts. While metal oxide phases formed for monometallic Pd and Cu under O-2-exposure, bimetallic PdCu and AuCu NCs showed loss of metallic Cu in the crystalline phases after exposure to O-2. However, upon introducing the bimetallic NCs to a reducing atmosphere, the Cu was found to reappear and reincorporate into a crystalline phase, forming the initial bimetallic structures. By combining TS, PDF analysis and in situ HR-TEM, we saw that Cu segregates to the NC surfaces or forms small CuO domains under O-2-exposure. Our results thus indicate that the Cu mobility promotes segregation and formation of CuO along with the formation of a monometallic phase, which ultimately changes the resulting active surface sites of the nanocatalyst. Understanding the dynamical structure-property relations of nanocatalysts is key to enable rational design of efficient and robust catalysts for controlled catalytic reactions.

AB - Bimetallic nanocrystals (NCs) often show improved catalytic activities compared to their monometallic counterparts, but to optimize the performance it is crucial to understand how they behave under actual reaction conditions, i.e. in gas environments. Here, we use powder X-ray diffraction (PXRD), total scattering (TS) with pair distribution function (PDF) analysis and in situ high-resolution transmission electron microscopy (HR-TEM) to provide new insights into the atomic-scale behaviour of NC catalysts under a reactive gas environment. By investigating Au, Cu, Pd, PdCu, AuPd and AuCu NCs, we observe that the properties of bimetallic NCs differ significantly from their monometallic counterparts. While metal oxide phases formed for monometallic Pd and Cu under O-2-exposure, bimetallic PdCu and AuCu NCs showed loss of metallic Cu in the crystalline phases after exposure to O-2. However, upon introducing the bimetallic NCs to a reducing atmosphere, the Cu was found to reappear and reincorporate into a crystalline phase, forming the initial bimetallic structures. By combining TS, PDF analysis and in situ HR-TEM, we saw that Cu segregates to the NC surfaces or forms small CuO domains under O-2-exposure. Our results thus indicate that the Cu mobility promotes segregation and formation of CuO along with the formation of a monometallic phase, which ultimately changes the resulting active surface sites of the nanocatalyst. Understanding the dynamical structure-property relations of nanocatalysts is key to enable rational design of efficient and robust catalysts for controlled catalytic reactions.

KW - INDUCED SURFACE SEGREGATION

KW - OXYGEN-REDUCTION ACTIVITY

KW - CATALYTIC-ACTIVITY

KW - CO2 HYDROGENATION

KW - OXIDE

KW - GOLD

KW - SIZE

KW - NANOPARTICLES

KW - OXIDATION

KW - METAL

U2 - 10.1039/d3ta00458a

DO - 10.1039/d3ta00458a

M3 - Journal article

VL - 11

SP - 9654

EP - 9667

JO - Journal of Materials Chemistry A

JF - Journal of Materials Chemistry A

SN - 2050-7488

IS - 17

ER -