Hierarchically Porous Monoliths Based on N‑Doped Reduced Titanium Oxides and Their Electric and Electrochemical Properties

Abstract

In this report, we demonstrate a novel synthesis method to obtain reduced titanium oxides with monolithic shape and with a well-defined hierarchically porous structure from the titanium-based network bridged with ethylenediamine. The hierarchically porous monoliths are fabricated by the nonhydrolytic sol–gel reaction accompanied by phase separation. This method allows a low-temperature crystallization into Ti₄O₇ and Ti₃O₅ at 800 and 900 °C, respectively, with N-doped carbon. These reduced titanium oxides are well-doped with N atoms even under argon atmosphere without NH₃, which accounts for the low-temperature reduction. The resultant monolithic materials possess controllable macropores and high specific surface area together with excellent electric conductivity up to 230 S cm^–1, indicating promise as a conductive substrate that can substitute carbon electrodes