Synthesis of High-Performance Titanium Sub-Oxides for Electrochemical Applications Using Combination of Sol–Gel and Vacuum-Carbothermic Processes

Abstract

A series of nanocrystalline titanium (Ti) sub-oxides, including TiO, Ti2O3, Ti3O5, and Ti4O7, with high surface area and activity are successively synthesized using a facile synthesis method that combines the sol–gel and the energy-efficient vacuum-carbothermic (SG-VC) processes. The combination results in synergy in producing nanomaterials with high surface area (>100 m2 g–1), good conductivity, and rich intra-grain defect features, giving the oxides unique surface activities suitable for particular electrochemical applications. The phase compositions of the resulting powders are primarily determined by two process parameters, including the carbothermic carbon (C) content, expressed as the C-to-Ti molar ratio of the reactant powder, and the cooling protocol. Carbothermic C contents exceeding a threshold of C/Ti ∼ 3.7 exclusively produced non-Magnéli phase (MP) oxides including TiO and Ti2O3, while the MP oxides, Ti3O5 and Ti4O7, can be formed only with lower C contents combined with selected quenching protocols that kinetically limit oxygen replenishment during cooling. Examples of the resulting MP Ti4O7 powder exhibiting outstanding pseudocapacitive and oxygen evolution reaction catalytic behaviors are demonstrated.

Switchable Intrinsic Defect Chemistry of Titania for Catalytic Applications

“…The state-of-the-art method to prepare reduce Titania (oxygen deficient) include energetic ion or electron beam implantation, UV irradiation, heating TiO 2 under vacuum, thermal annealing to high temperatures (above 500 K), reducing conditions (C, H 2 ), plasma-treating, laser, and high-energy particle (neutron, Ar + , electron, or γ-ray) bombardment, chemical vapor deposition, vacuum activation, metal reduction, electrochemical reduction, partial oxidation starting from Ti, Ti(II) and Ti(III) precursors, etc. [68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83].…”

Different Reactivity of Rutile and Anatase TiO2 Nanoparticles: Synthesis and Surface States of Nanoparticles of Mixed‐Valence Magnéli Oxides

“…[17] However, mosto ft he materials reported abovea re produced in two main separatew ays. [5,7,8,[18][19][20][21] These residues confine the oxide during the transformation of TiO 2 into MagnØli phases and enable recovery of nanostructured materials. It unavoidably produces carbon residues, which accountf or about 2-20 wt %o ft he products.…”

“…It unavoidably produces carbon residues, which accountf or about 2-20 wt %o ft he products. [5,7,8,[18][19][20][21] These residues confine the oxide during the transformation of TiO 2 into MagnØli phases and enable recovery of nanostructured materials. However,c arbonaceous moieties are present at the surface of the MagnØli material.…”

Dismutation of Titanium Sub‐oxide into TiO and TiO2 with Structural Hierarchy Assisted by Ammonium Halides

“…Herein, we first report the disproportionation reaction of titanium sub-oxides (Ti n O 2nÀ1 )i na mmonium halide (NH 4 X) atmosphere to produce different proportions of TiOa nd TiO 2 with black colour.F urthermore, the conductivity and light absorptivity can be greatly improved by in situ growth of ac onductive TiOl ayer on the surface of black TiO 2Àx , [12] which is similar to metal particles with LSPR properties. [4a] Ti n O 2nÀ1 are a class of titaniumo xides with great conductivity, [13] unique structures, [14] chemical stabilitya nd corrosion resistance, [15] such as Ti 2 O 3 ,T i 3 O 5 and Ti 4 O 7 .I no ther words,T i n O 2nÀ1 have lower oxygen to titanium ratios. [13] It is reasonable to expect that Ti n O 2nÀ1 can turn into TiO 2Àx after propero xidation or iondoping treatment.…”