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On the high structural heterogeneity of Fe-impregnated graphitic-carbon catalysts from Fe nitrate precursor

DOI: 10.3390/catal9040303 DOI Help

Authors: Rosa Arrigo (University of Salford; Diamond Light Source) , Manfred Erwin Schuster (Johnson Matthey Technology Centre)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Catalysts , VOL 9

State: Published (Approved)
Published: March 2019

Open Access Open Access

Abstract: Wet impregnation is broadly applied for the synthesis of carbon-supported metal/metal oxide nanostructures because of its high flexibility, simplicity and low cost. By contrast, impregnated catalysts are typified by a usually undesired nanostructural and morphological heterogeneity of the supported phase resulting from a poor stabilization at the support surface. This study on graphite-supported Fe-based materials from Fe nitrate precursor is concerned with the understanding of the chemistry that dictates during the multistep synthesis, which is key to designing structurally homogeneous catalysts. By means of core-level X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy and atomic resolution electron microscopy, we found not only a large variety of particles sizes and morphologies but also chemical phases. Herein, thermally stable single atoms and few atoms clusters are identified together with large agglomerates of an oxy-hydroxide ferrihydrite-like phase. Moreover, the thermally induced phase transformation of the initially poorly ordered oxy-hydroxide phase into several oxide phases is revealed, together with the existence of thermally stable N impurities retained in the structure as Fe–N–O bonds. The nature of the interactions with the support and the structural dynamics induced by the thermal treatment rationalize the high heterogeneity observed in these catalysts.

Journal Keywords: errihydrite; Fe2p; O1s; N1s XPS; NEXAFS; HAADF-STEM

Subject Areas: Materials, Chemistry

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E01-JEM ARM 200CF

Documents:
catalysts-09-00303-v2 (1).pdf