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

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-Magn?li 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. ? 2018 American Chemical Society.