Abstract
Preparation of the Magnéli Ti4O7 reactive electrochemical membrane (REM) with high purity is of great significance for its application in electrochemical advanced oxidation processes (EAOPs) for wastewater treatment. In this study, the Ti4O7 REM with high purity was synthesized by mechanical pressing of TiO2 powders followed by thermal reduction to Ti4O7 using the Ti powder as the reducing reagent, where the TiO2 monolith and Ti powder were separated from each other with the distance of about 5 cm in the vacuum furnace. When the temperature was elevated to 1333 K, the Magnéli phase Ti4O7 REM with the Ti4O7 content of 98.5% was obtained after thermal reduction for 4 h. Noticeably, the surface and interior of the obtained REM bulk sample has a homogeneous Ti4O7 content. Doping carbon black (0wt%-15wt%) could increase the porosity of the Ti4O7 REM (38–59%). Accordingly, the internal resistance of the electrode and electrolyte and the charge-transfer impedance increased slightly with the increasing carbon black content. The optimum electroactive surface area (1.1 m2) was obtained at a carbon black content of 5wt%, which increased by 1.3-fold in comparison with that without carbon black. The as-prepared Ti4O7 REMs show high oxygen evolution potential, approximately 2.7 V/SHE, indicating their appreciable electrocatalytic activity toward the production of •OH.
Highlights
Ceramic porous sub-stoichiometric Ti oxides (TinO2n-1, 4≤n ≤ 10), known as Magnéli phases, were first synthesized and characterized in the 1950s (Zhou et al, 2018)
When the temperature was elevated to 1333 K, the X-ray diffraction (XRD) patterns show the characteristic peaks for Ti4O7, and almost no peaks for other Magnéli phases suggests that a high purity Magnéli phase Ti4O7
The high purity Ti4O7 reactive electrochemical membrane (REM) was successfully synthesized by mechanical pressing of TiO2 powders followed by thermal reduction to Ti4O7 using the Ti powder as the reducing reagent
Summary
Ceramic porous sub-stoichiometric Ti oxides (TinO2n-1, 4≤n ≤ 10), known as Magnéli phases, were first synthesized and characterized in the 1950s (Zhou et al, 2018). Among these oxides, Ti4O7 exhibits excellent performance owing to its unique structure, e.g., excellent corrosion resistance and outstanding electrical conductivity with a value of 1000 S cm−1, which is higher than the 727 S cm−1 of graphitized carbon (Walsh and Wills, 2010). Depositing Ti4O7 films at the Ti surface has been manufactured successfully by the plasma coating approach, which is a widely spread technology for many types of applications (corrosion protection, abrasion resistance, thermal barriers, etc.) REMs based on electrochemical advanced oxidation processes (EAOPs) are a cutting edge class of electrodes that hold great promise in revolutionizing water/ wastewater treatment (Zaky and Chaplin, 2013)
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