Conversion of Potassium Titanate Nanowires into Titanium Oxynitride Nanotubes

Abstract

Tunnel-structured potassium titanate with a K(3)Ti(8)O(17) phase was synthesized by direct oxidation of titanium powder mixed with KF(aq) in water vapor at 923 K. The reaction conditions were adjusted so that uniform single crystalline potassium titanate nanowires with [010] growth direction (length: 5-30 μm, diameter: 80-100 nm) were obtained. Nitridation of the nanowires by NH(3)(g) at 973-1073 K converted the titanate nanowires into rock-salt structured cubic phase single crystalline titanium oxynitride TiN(x)O(y) nanotubes (x = 0.88, y = 0.12, length = 1-10 μm, diameter = 150-250 nm, wall thickness = 30 - 50 nm) and nanorods (x = 0.5, y = 0.5, length = 1-5 μm, diameter = 100-200 nm) with rough surfaces and [200] growth direction. The overall conversion of the titanate nanowires into the nanotubes and the nanorods can be rationalized by Ostwald ripening mechanism. We fabricated an electrode by adhering TiN(x)O(y) nanotubes (0.2 mg) on a screen-printed carbon electrode (geometric area: 0.2 cm(2)). Electrochemical impedance spectroscopy demonstrated its charge transfer resistance to be 20Ω. The electrochemical surface area of the nanotubes on the electrode was characterized by cyclic voltammetry to be 0.32 cm(2). This property suggests that the TiN(x)O(y) nanostructures can be employed as potential electrode materials for electrochemical applications.

Metal Oxynitrides as Promising Electrode Materials for Supercapacitor Applications

“…[168] In case of TiONs, the presence of oxide phase aids in rapid surface redox reactions. [169][170][171][172] In the context of TiONs, This result is akin to the other TiN structures reported such as nanofibers (145 F g À 1 @2 mV s À 1 ) [173] and nanowires (123 F g À 1 @10 mV s À 1 ). By varying the O/N ratio, the properties of the oxynitride can be modified.…”

“…By varying the O/N ratio, the properties of the oxynitride can be modified. [169][170][171][172] In the context of TiONs, This result is akin to the other TiN structures reported such as nanofibers (145 F g À 1 @2 mV s À 1 ) [173] and nanowires (123 F g À 1 @10 mV s À 1 ). [46] The performance of TiO x N y nanosheets attributes to porous morphology and divalent cations in nanosheets.…”

N-doped titanate nanostructures on gradient surface layer of one dimensional nanofibers synthesized on Ti electrode by chemical and thermal treatments

“…This proposition is in agreement with the reported results on the conversion of potassium titanate to Ti-oxynitrides. 33 A similar mechanism of formation of Ti-oxynitride can be expected in CT800, but with a higher reaction rate of nitridation, due to the increase in temperature to 800 C, resulting in an enhanced doping level of N in H-titanate to transform into a large amount of Ti-oxynitride as shown by the higher peak intensity of Ti-oxynitride in CT800 (Fig. 1).…”

“…The formation of TiO can be expected during high temperature nitridation of titanates, which is in close agreement with the recent report on the conversion of potassium titanate to TiO by heat treatment at 800 C in an NH 3 atmosphere. 33 In addition, Ti-oxynitrides were detected by XRD measurements of CT700 and CT800. It is suggested that the poorly crystallized structure of the H-titanate precursor provides excellent channels for the diffusion of N, and readily substitutes O and bonds to Ti atoms to form Ti-oxynitrides.…”

Controlling Disorder and Superconductivity in Titanium Oxynitride Nanoribbons with Anion Exchange

“…the nitridation stage, TiO 2 converts to titanium oxynitride, Ti(O,N) x (x  1) by substituting oxygen with nitrogen atoms: TiO 2 (s) + NH 3 (g)  Ti(O,N) x (s) + H 2 O(g). 34 Since the nitridation process is a nitrogen diffusion-controlled reaction 28,35,36 , the nitrogen content in Ti(O,N) nanoribbons can be controlled by varying the reaction parameters. Therefore, we set the same temperature of 800 °C for all nitridation reactions, but used different values of NH 3 (g) flow while systematically changing the reaction times (Table S1).…”