Hydrogen Production from Low-Grade Water Electrolysis to Contribute to Sustainable Development Goals 6 and 7: Challenges and Opportunities

The nexus between water and energy plays a key role in the green hydrogen economy. Conventional water electrolyzers require high purity water. This can create a burden on fresh water facilities, in water stressed regions, for the mass production of green hydrogen. In this context, this work explores the potential of non-potable water sources, such as untreated sea and brackish water and wastewater, as feedstock for water electrolyzers to produce green hydrogen, thereby contributing to UN’s sustainable development goals 6 and 7. We discuss the ionic impurities composition, variability of these low-grade water types and electrochemical challenges arising from these impurities. This includes undesired reactions, scaling, and catalyst and membrane degradation. We highlight the strategies to overcome these challenges, i.e. design of electrocatalysts like Brønsted acid oxide coatings and design of electrolyzers such as membrane-less flow water electrolyzer that leverages hydrodynamic flow to separate the produced hydrogen and oxygen gasses without the costly and impurity sensitive membranes. We further propose the integration of flow electrolyzers with wastewater pipelines to support the decentralized hydrogen production. These advances can pave the pathway toward resource efficient and decentralized hydrogen production that aligns with global sustainability and clean energy goals. This perspective includes some new experimental data to illustrate the proposed approach for membrane free electrolyzer for low-grade water electrolysis.