Publication date: 22nd July 2026
In heterogeneous catalytic systems, active metallic species are often supported on metal oxides. The deposited nanoparticles (NPs), however, often suffer from sintering, which can lead to deactivation of the catalyst. An alternative fabrication route for catalysts involves direct exsolution of metallic NPs from doped metal oxide hosts under thermal reductive treatments.[1] This approach can produce highly active and stable catalysts, where the exsolved NPs can remain strongly anchored to the host oxide.[1]
In our recent work, we demonstrate tunable exsolution of multimetallic NPs from a series of compositionally complex first-row transition metal spinel oxides.[2] We track the electronic, atomic structural, and microstructural evolution of the host oxide and exsolved NPs during thermal reductive treatment in diluted H2 by in situ X-ray diffraction and total scattering followed by Rietveld and pair distribution function analysis. The results are complemented by electron microscopy and near-ambient pressure X-ray photoelectron spectroscopy. We observe exsolution of Cu-rich NPs from ca. 360 °C, while Cu@NiCo core-shell NPs form at 500 °C, which subsequently alloy into trimetallic CuNiCo NPs at 700 °C. Furthermore, we demonstrate that compositional tuning of the host oxide significantly affects the exsolution mechanisms, allowing tuning of the overall process. Our findings identify compositionally complex solid solutions as promising platforms for the rational design of innovative exsolved catalysts.
A.K. acknowledges the Ministry of Culture and Science of the State of North Rhine-Westphalia for funding under the NRW Returnee Fellowship (NRW Rückkehrerprogramm). This work was funded in part by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, 2018/01258-5, 2020/12986-1, 2023/02561- 1, 2023/09379-4, 2025/12532-4), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, 311226/2022-1, 405800/2022-3, and 409401/2023-4), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES finance code 18 001). This work has been part to the Centre of High Entropy Catalysis (CHEAC) and Danish National Research Foundation (DNRF149) which we are grateful for the funding. We acknowledge Diamond Light Source for time on I15-1 under proposal CY36148. We acknowledge MAX IV Laboratory for time on HIPPIE beamline under Proposal 20240465. The authors thank the Brazilian Nanotechnology National Laboratory (LNNano) and the Brazilian Synchrotron Light Laboratory (LNLS), open national facilities operated by the Brazilian Center for Research in Energy and Materials (CNPEM) of the Brazilian Ministry for Science, Technology, Innovations, and Communications (MCTIC), for access to TEM (proposal BAG 20233144) and Paineira beamline (proposal 20253057) facilities. The Danish Research Council is acknowledged for covering travel expenses for the synchrotron experiments (DanScatt).
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