Unlocking the potential in municipal reclaimed water electrolysis for hydrogen production: Identification of the primary water matrix.

Authors

Zongping Wang, Haoran Chen, Zhenbin Chen, Yunfei Li, Ang Lu, Yujie Cheng, Guosen Zhang, Ge Li, Shunjie Zhu, Lin Li, Lizhi Huang, Jiakun Fang, Qunlei Wen, Jun Ma, Pengchao Xie

Published in

Water research. Volume 304. Pages 126378. Jun 28, 2026. Epub Jun 28, 2026.

Abstract

Electrolytic hydrogen production is constrained by freshwater scarcity and the spatial mismatch between renewable energy resources and water availability. Direct municipal reclaimed water (MRW) electrolysis offers a sustainable route by producing hydrogen while reusing co-produced oxygen for wastewater aeration. Here, we show that MRW electrolysis under industrially relevant conditions achieves hydrogen purity and Faradaic efficiency comparable to deionized water electrolysis, yet requires higher energy input. Systematic evaluation of water matrix constituents identifies calcium-induced oxygen evolution reaction (OER) inhibition as the dominant bottleneck, while the hydrogen evolution reaction remains largely unaffected. Distinct from the conventional focus on Ca/Mg induced cathodic scaling and mass-transfer blockage, our results reveal a previously unrecognized anodic calcium-specific inhibition mechanism that directly limits OER activity. Integrated experimental and theoretical analyses demonstrate that preferential Ca²⁺ adsorption perturbs the local electronic structure of the electrode, alters OER intermediates, reduces the affinity of active sites for hydroxide ions, and ultimately impedes oxygen evolution. Given the widespread presence of Ca²⁺ in low-grade water sources, this anodic inhibition mechanism represents a critical yet overlooked constraint for direct water electrolysis beyond conventional cathodic scaling. These findings emphasize the need to consider Ca²⁺ tolerance in anode design and provide guidance for developing durable, impurity-tolerant electrolysis systems.

PMID:
42391651
Bibliographic data and abstract were imported from PubMed on 03 Jul 2026.

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