Single sheet iron oxide: An efficient heterogeneous electro-Fenton catalyst at neutral pH

• Published in: Journal of hazardous materials 2019-02, Vol.364, p.39-47
• Main Authors: Huang, Li-Zhi, Zhu, Mingtao, Liu, Zizheng, Wang, Zongping, Hansen, Hans Christian B.
• Format: Article
• Language: English
• Subjects: Advanced oxidation processes; Electro-Fenton; Green rust; Heterogeneous electro catalyst; Single sheet iron oxide
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2018.10.026

[Display omitted] •The reactivity of SSI as a heterogeneous electro-Fenton catalyst is much higher than its homogenous counterparts.•Hydroxyl radicals (OH) and superoxide (O2–) are produced on SSI cathode during electrolysis.•The SSI electrode is highly stable at least up to 19 cycles and use for 190 h.•The reactivity of SSI electrode was almost the same in the pH range from 7 to 10.•Azo dyes are degraded on SSI cathode via both direct reduction and radical-involved oxidation. In order to overcome the inefficiency of heterogeneous electro-Fenton process for water treatment at neutral pH, single sheet iron oxide (SSI) derived from layered Fe(II)-Fe(III) double hydroxides (green rusts) was fabricated on an indium tin oxide electrode via layer by layer assembly and used in an undivided electrolysis cell. Use of radical scavengers demonstrated the formation of oxygen radicals by electrochemical reduction of oxygen at the SSI electrode, and the key role of hydroxyl radicals (OH) and superoxide anion (O2–) radicals in degradation of the azo dye orange II. Analysis of degradation products by UV–vis, LC–MS and GC–MS further demonstrated that direct reduction toke place in addition to indirect oxidation. The reactivity of SSI as a heterogeneous electro-Fenton catalyst is two order of magnitude higher than its homogenous counterparts. The SSI electrode was highly stable as the dye degradation did not decrease after use for 19 h with no Fe leaching. The high dye removal efficiency was maintained in a wide pH range from 7 to 10 and in different supporting electrolytes, demonstrating the application of this process under various conditions mimicking natural waters.