Scalable Ir-Doped NiFe2O4/TiO2 Heterojunction Anode for Decentralized Saline Wastewater Treatment and H2 Production
Sukhwa Hong, Jiseon Kim, Jaebeom Park, Sunmi Im, Michael R. Hoffmann, Kangwoo Cho
Abstract
Abstract Wastewater electrolysis cells (WECs) for decentralized wastewater treatment/reuse coupled with H 2 production can reduce the carbon footprint associated with transportation of water, waste, and energy carrier. This study reports Ir-doped NiFe 2 O 4 (NFI, ~ 5 at% Ir) spinel layer with TiO 2 overlayer (NFI/TiO 2 ), as a scalable heterojunction anode for direct electrolysis of wastewater with circumneutral pH in a single-compartment cell. In dilute (0.1 M) NaCl solutions, the NFI/TiO 2 marks superior activity and selectivity for chlorine evolution reaction, outperforming the benchmark IrO 2 . Robust operation in near-neutral pH was confirmed. Electroanalyses including operando X-ray absorption spectroscopy unveiled crucial roles of TiO 2 which serves both as the primary site for Cl − chemisorption and a protective layer for NFI as an ohmic contact. Galvanostatic electrolysis of NH 4 + -laden synthetic wastewater demonstrated that NFI/TiO 2 not only achieves quasi-stoichiometric NH 4 + -to-N 2 conversion, but also enhances H 2 generation efficiency with minimal competing reactions such as reduction of dissolved oxygen and reactive chlorine. The scaled-up WEC with NFI/TiO 2 was demonstrated for electrolysis of toilet wastewater.