Author: Ronghui Qi (South China University of Technology) - Green hydrogen production via water electrolysis driven by renewable energy aligns with sustainable energy development goals. Compared to alkaline electrolysers, proton exchange membrane (PEM) electrolysers exhibit greater responsiveness, allowing effective adaptation to the fluctuating power input from solar and wind energy sources. However, conventional electrolysis methods typically depend on purified freshwater. To facilitate direct hydrogen production from abundant seawater resources, this study developed a novel membrane-based PEM electrolyser by coupling photothermal membrane distillation with PEM electrolysis in situ. The integrated device employs a composite moisture-permeable membrane that can also absorb solar irradiation, converting it into thermal energy. This photothermal effect generates water vapour directly from seawater, which subsequently diffuses directly (no need pump) through the membrane into the PEM electrolyser's anode. Experimental tests demonstrated that under standard solar irradiation conditions (1 sun), the integrated electrolysis system achieved stable performance at an operational voltage of 2 V and current density of 500 mA/cm², producing hydrogen at a rate of 2163 Nm³/h. This performance is equivalent to that obtained when seawater is externally preheated to 70°C without photothermal assistance, highlighting the advantage of energy saving. Durability testing confirmed the stability with a performance degradation of less than 5% observed after 250 hours of continuous operation in a 3.5 wt.% NaCl saline solution. The design integrates photovoltaic-driven electrolysis and photothermal membrane distillation in situ, thereby achieving combined electrical and thermal energy self-sufficiency. The proposed membrane-based electrolyser offers a durable and high-performance solution for efficient and sustainable hydrogen production directly from seawater, significantly reducing freshwater dependency and associated treatment costs.
