The Superior Electrical Conductivity and Anodic Stability of Vanadium-Doped Ti₄O₇

Abstract

The effectiveness of Magnéli phase titanium oxides (Ti n O 2n−1 , 4 ⩽ n ⩽ 10), promising alternatives to carbon-based materials in aqueous electrochemical technologies, is limited by their instability at strongly oxidizing electrode potentials. Ti 4 O 7 and Ti 5 O 9 , the most electrically-conductive Ti n O 2n−1 , passivate in the harsh conditions demanded by fuel cells, batteries, and devices for the electrochemical treatment of water. Among other properties relevant to electrodes, doping of Ti n O 2n−1 with transitional metals vanadium, chromium, and iron improves the oxidation stability as demonstrated by higher onset temperatures in the thermograms of doped Ti 4 O 7 heated in air. To investigate the influence of doping on their anodic stability, disk electrodes of Ti 4 O 7 doped with V, Cr, and Fe were investigated by electrochemical accelerated life testing (ALT). These disks, prepared by high-temperature H 2 reduction of nominally 2 at% doped titanium(IV) oxide (TiO 2 ), were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), the 4-point probe method, cyclic voltammetry (CV), Tafel plot analysis, and electrochemical impedance spectroscopy (EIS). V-and Fe-doping are shown to improve the electrical conductivity and V-doping is demonstrated to improve the anodic stability as measured by the mean time-to-failure (TTF) during electrochemical ALT.

Vanadium-Doped Ti4O7 Porous Transport Layers for Efficient Electrochemical Oxidation of Industrial Wastewater Contaminants

“…38 The superiority of the electrical conductivity of (Ti 1-x V x ) 4 O 7 for x > 0 is attributed to the presence of vanadium, whose increasing concentration in Ti 4 O 7 is observed to reduce its electrical resistivity. 58 Compared with our previous report, 38 a further improvement in the electrical conductivity of the materials used currently is attributed to a longer time and higher temperature of sintering, which is expected to improve fusion between grains and therefore decrease the electrical resistance between particles. Values of electrical conductivity are still less than those observed for singlecrystal measurements of Ti 4 O 7 : 1,000-2,000 S cm −1 .…”

“…Over a range of 0.1-10 mA cm −2 , the cell voltage in supporting electrolyte increases from that near the equilibrium cell potential for the electrolysis of water, 1.23 V, to that approaching 5 V. As discussed earlier, Ti 4 O 7 as well as (Ti 0.98 V 0.02 ) 4 O 7 are poor electrocatalysts for the water splitting reactions including the OER. 38,61 Additionally, the cathode compartment is composed of a carbon-based GDL, which exhibited modest catalytic behavior toward the complementary water splitting reaction (Fig. S2).…”

“…intercalation of charge carriers, respectively. 35 Alternatively, doping with cerium 36 and vanadium 37,38 is shown to improve resilience to passivation of Ti 4 O 7 attributed to improved thermodynamic and structural stability. 39 Herein, we report upon our investigation using a compact wastewater electrolyzer for the EO of MO in synthetic wastewater, using porous transport layers (PTLs) of anodically-stable vanadiumdoped Ti 4 O 7 .…”

Structural and electronic properties of Ce‐doped Ti4O7 based on experiments and first‐principles calculations

“…There have been some studies on the electrochemical properties of doped Ti 4 O 7 . According to English et al, 31 V and Fe as dopants can improve the electronic conductivity of Ti 4 O 7 due to the increased carrier concentration, and the V-doped Ti 4 O 7 anode exhibited greater stability in the oxygen evolution process (H 2 O → O 2 + H + + e − ). Xu et al 32 prepared La-doped Ti 4 O 7 electrodes and found that the doped electrodes provided a higher number of surface oxygen vacancies, resulting in increased •OH generation efficiency (Reaction 3).…”

“…There have been some studies on the electrochemical properties of doped Ti 4 O 7 . According to English et al., 31 V and Fe as dopants can improve the electronic conductivity of Ti 4 O 7 due to the increased carrier concentration, and the V‐doped Ti 4 O 7 anode exhibited greater stability in the oxygen evolution process (H 2 O → O 2 + H + + e − ). Xu et al 32 .…”