XPS characterization of Mo-Nb mixed-oxide nanorod arrays via the anodizing of thin Al/Mo-Nb-alloy bilayers on substrates

XPS characterization of Mo-Nb mixed-oxide nanorod arrays via the anodizing of thin Al/Mo-Nb-alloy bilayers on substrates

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Molybdenum oxides form a large group of materials resulting from the ability of Mo to possess different formal oxidation states and local coordinations, which may give rise to mixed-valency oxides indispensable for energy storage, gas sensing, electrochromic or catalytic applications. Nanostructuring and doping molybdenum oxides with foreign elements or mixing with similar or dissimilar metal oxides may substantially advance the properties of the individual oxide, although such an approach typically requires exceptionally high temperatures, high vacuum, and high-budget equipment. In this work, we present an alternative approach to creating arrays of molybdenum oxide mixed with niobium oxide nanostructures via a simple, self-organized, room-temperature electrochemical anodizing of thin Al layers superimposed on thin Mo-Nb metal-alloy layers of variable component concentrations prepared by the magnetron sputter-deposition. Anodizing was carried out in oxalic acid solution, forming porous anodic alumina (PAA), followed by PAA-assisted oxidation of the alloy underlayers, and finishing with selective dissolution of the PAA overlayers. Detailed X-ray photoelectron spectroscopy (XPS) analysis of Mo 3d and Nb 3d narrow-scan spectra revealed that the highest amount of Mo in the nanostructures' surface was 79 at.% (Mo+Nb=100 at.%). The dominating molybdenum-oxide component comprised Mo cations with various oxidation states (Mo6+, Mo5+, Mo4+, and Mo3+), whereas the niobium-oxide inclusions were mostly Nb2O5. The success of preparing and analyzing the Mo-Nb mixed-oxide nanostructures is vital for understanding the formation-structure-morphology relationship and exploring the functional properties of the novel nanoarrays.

Molybdenum oxides form a large group of materials resulting from the ability of Mo to possess different formal oxidation states and local coordinations, which may give rise to mixed-valency oxides indispensable for energy storage, gas sensing, electrochromic or catalytic applications. Nanostructuring and doping molybdenum oxides with foreign elements or mixing with similar or dissimilar metal oxides may substantially advance the properties of the individual oxide, although such an approach typically requires exceptionally high temperatures, high vacuum, and high-budget equipment. In this work, we present an alternative approach to creating arrays of molybdenum oxide mixed with niobium oxide nanostructures via a simple, self-organized, room-temperature electrochemical anodizing of thin Al layers superimposed on thin Mo-Nb metal-alloy layers of variable component concentrations prepared by the magnetron sputter-deposition. Anodizing was carried out in oxalic acid solution, forming porous anodic alumina (PAA), followed by PAA-assisted oxidation of the alloy underlayers, and finishing with selective dissolution of the PAA overlayers. Detailed X-ray photoelectron spectroscopy (XPS) analysis of Mo 3d and Nb 3d narrow-scan spectra revealed that the highest amount of Mo in the nanostructures' surface was 79 at.% (Mo+Nb=100 at.%). The dominating molybdenum-oxide component comprised Mo cations with various oxidation states (Mo6+, Mo5+, Mo4+, and Mo3+), whereas the niobium-oxide inclusions were mostly Nb2O5. The success of preparing and analyzing the Mo-Nb mixed-oxide nanostructures is vital for understanding the formation-structure-morphology relationship and exploring the functional properties of the novel nanoarrays.

Anodic oxidation, metal oxides, molybdenum, niobium, X-ray photoelectron spectroscopy

Anodic oxidation, metal oxides, molybdenum, niobium, X-ray photoelectron spectroscopy

BENDOVÁ, M.; PRÁŠEK, J.; MOZALEV, A.

2026

28.02.2025

TANGER LTD

978-80-88365-24-2

Proceedings 16th International Conference on Nanomaterials - Research & Application

272

277

6

https://www.confer.cz/nanocon/2024/4993-xps-characterization-of-mo-nb-mixed-oxide-nanorod-arrays-via-the-anodizing-of-thin-al-mo-nb-alloy-bilayers-on-substrates

http://hdl.handle.net/11012/249384