Ellipsometric study of anodic oxide films formed on niobium surfaces

Towards Replacing Titanium with Copper in the Bipolar Plates for Proton Exchange Membrane Water Electrolysis

“…Consequently, the thicknesses of the passive films formed before/after polarization at 2 V for 6 h were estimated to be 1.0 nm/6.7 nm (metallic Nb), 2.5 nm/9.5 nm (NbCu8L), and 2.5 nm/10.9 nm (NbCu16L and 2.7/13.0 nm (NbCu32L)), respectively. These results are consistent with literature data [ 32 ], which indicate a thickness of about 1 nm for the air-formed natural oxide film and about 10 nm at 2 V for anodically grown oxide films on the Nb surface after fine mechanical polishing.…”

“…The excellent corrosion resistance properties of Nb are due to its ability to passivate spontaneously in contact with oxygen from air or aqueous environments, by forming a thin, highly adherent and stable passive oxide layer on its surface. The thickness of this oxide layer is 2–4 nm and it is extremely difficult to remove from the metal surface [ 32 , 33 ]. The corrosion resistance of Nb can be further increased by electrochemical formation of passive oxide films on its surface.…”

“…The corrosion resistance of Nb can be further increased by electrochemical formation of passive oxide films on its surface. The chemical composition of the anodic oxide film has been found to depend on the presence of the natural air-formed oxide film and consists of more or less stable oxides, such as NbO, NbO 2 , and Nb 2 O 5 [ 32 , 33 ]. During anodic polarization, NbO 2 is irreversibly oxidized to Nb 2 O 5 and Nb is reversibly oxidized to NbO.…”

Platinum Supported on NbRuyOz as Electrocatalyst for Ethanol Oxidation in Acid and Alkaline Fuel Cells

“…The deactivation is most likely related to the native oxide layer niobium forms regardless of the oxidation state of the bulk. The thickness of this layer is usually reported to be on the order of <1 to 6 nm, , though this can vary significantly for niobium in various liquid electrolyte . It is not immediately clear how an oxide layer of this type would fully deactivate Pt nanoparticles 2−20 nm or more in diameter, especially after the reducing treatments employed above.…”

Reflectivity from electrochemically protected Nb surfaces

“…Over the last forty years we can also find the data for reflectivity at pseudo Brewster's angle of electro-polished metal surfaces with cathodic pre-treatment and measured at in-situ conditions during the cathodic polarization [7,8]. Many previous results confirmed that with electro-polishing the most of surface impurities are dissolved in solution of electro-polishing baths and with cathodic polarization the thickness of natural oxide film is minimized [2,9]. But still is arguable possible inclusion of anions from electro-polishing bath in the crystals of metal surfaces.…”