Thermally symbiotic integration of osmotic membrane distillation and electrolysis for direct seawater hydrogen production

Abstract Integrating water purification membranes with electrolysis for in situ hydrogen (H 2 ) production from seawater offers a rapid pathway to net-zero, but is limited by salt crossover and insufficient water production in existing approaches. Here we overcome these limitations by integrating osmotic membrane distillation (OMD) with alkaline water electrolysis (AWE). Driven by dual thermal and osmotic gradients to enhance salt-free water vapour transport, the OMD-AWE delivers a H 2 production rate of 60 kg m –2 day –1 with excellent stability over 500 h of continuous operation. To eliminate the external heating energy penalty of OMD, we propose a thermally symbiotic architecture that converts the AWE’s waste heat to OMD’s thermal driving force while OMD simultaneously providing cooling to maintain AWE optimal temperatures, as validated by our thermal-water-hydrogen model. This thermal symbiosis not only makes OMD-AWE energy self-sufficient with energy efficiency of 51 kWh kg(H 2 ) –1 but also establishes a self-regulating mechanism that phase-locks thermal driving force to fluctuating electrical inputs, synchronising water supply with demand to overcome renewable intermittency. Our approach enables flexible component matching and thermal self-sufficiency at any scale, providing a framework for membrane-integrated electrolysis, demonstrating both technical excellence and economic viability towards a sustainable hydrogen economy.