Scalable Ir-Doped NiFeO/TiO Heterojunction Anode for Decentralized Saline Wastewater Treatment and H Production.

Wastewater electrolysis cells (WECs) for decentralized wastewater treatment/reuse coupled with H production can reduce the carbon footprint associated with transportation of water, waste, and energy carrier. This study reports Ir-doped NiFeO (NFI, ~ 5 at% Ir) spinel layer with TiO overlayer (NFI/TiO), 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 marks superior activity and selectivity for chlorine evolution reaction, outperforming the benchmark IrO. Robust operation in near-neutral pH was confirmed. Electroanalyses including operando X-ray absorption spectroscopy unveiled crucial roles of TiO which serves both as the primary site for Cl chemisorption and a protective layer for NFI as an ohmic contact. Galvanostatic electrolysis of NH-laden synthetic wastewater demonstrated that NFI/TiO not only achieves quasi-stoichiometric NH-to-N conversion, but also enhances H generation efficiency with minimal competing reactions such as reduction of dissolved oxygen and reactive chlorine. The scaled-up WEC with NFI/TiO was demonstrated for electrolysis of toilet wastewater.