Scalable Ir-Doped NiFe2O4/TiO2 Heterojunction Anode for Decentralized Saline Wastewater Treatment and H2 Production
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1.
Pohang University of Science and Technology
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2.
California Institute of Technology
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3.
Yonsei University
Abstract
Wastewater electrolysis cells (WECs) for decentralized wastewater treatment/reuse coupled with H2 production can reduce the carbon footprint associated with transportation of water, waste, and energy carrier. This study reports Ir-doped NiFe2O4 (NFI, ~ 5 at% Ir) spinel layer with TiO2 overlayer (NFI/TiO2), 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/TiO2 marks superior activity and selectivity for chlorine evolution reaction, outperforming the benchmark IrO2. Robust operation in near-neutral pH was confirmed. Electroanalyses including operando X-ray absorption spectroscopy unveiled crucial roles of TiO2 which serves both as the primary site for Cl− chemisorption and a protective layer for NFI as an ohmic contact. Galvanostatic electrolysis of NH4+-laden synthetic wastewater demonstrated that NFI/TiO2 not only achieves quasi-stoichiometric NH4+-to-N2 conversion, but also enhances H2 generation efficiency with minimal competing reactions such as reduction of dissolved oxygen and reactive chlorine. The scaled-up WEC with NFI/TiO2 was demonstrated for electrolysis of toilet wastewater.
Copyright and License
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material.
Acknowledgement
This work was financially supported by the National Research Foundation of Korea (NRF) grants (2022R1A2C4001228, 2022M3H4A4097524, 2022M3I3A1082499, and 2021M3I3A1084818), and the Technology Innovation Program (20026415) of the Ministry of Trade, Industry & Energy (MOTIE, Korea). The authors also acknowledge the supports from Nanopac for fabrication of scaled-up reactor.
Contributions
Sukhwa Hong performed writing—original, visualization, methodology, and validation. Jiseon Kim presented formal analysis, investigation, and validation. Jaebeom Park contributed formal analysis and investigation. Sunmi Im conducted formal analysis and investigation. Michael R. Hoffmann provided resources and conceptualization. Kangwoo Cho carried out supervision, writing—review & editing, project administration, funding acquisition, and conceptualization.
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Additional details
- National Research Foundation of Korea
- 2022R1A2C4001228
- National Research Foundation of Korea
- 2022M3H4A4097524
- National Research Foundation of Korea
- 2022M3I3A1082499
- National Research Foundation of Korea
- 2021M3I3A1084818
- Ministry of Trade, Industry and Energy
- Technology Innovation Program 20026415
- Accepted
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2024-09-23Accepted
- Available
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2024-10-28Published online