A semi-vapor electrolysis technology for hydrogen generation from wide water resources

Cost-effective and scalable green hydrogen production from water electrolysis is crucial to achieve a net-zero emission future. Progress on water electrolysis technologies has long been made towards materials design and device assembly optimization to improve cost effectiveness. However, an expensive iridium-based electrocatalyst, pure water feedstock, low current density, and energy efficiency limit state-of-the-art water electrolysis, i.e., alkaline and polymer exchange membrane water electrolyzers based on liquid water feeding for large-scale implementation. Here, we propose a new semi-vapor electrolysis (SVE) system for cost-effective hydrogen generation that adopts low temperature vapor electrolysis at the anode while maintains liquid water circulation at the cathode. The SVE process requires no additional energy input as compared to the conventional liquid water electrolysis process while enabling the direct use of a wide range of water resources without pre-treatment. In addition, much cheaper and intrinsically more active ruthenium oxide can be used under the conditions of SVE by avoiding dissolution, which achieves an ultrahigh current density of 4.67 A cm⁻² at 1.8 V and superior stability under 1.0 A cm⁻² operation. Techno-economic assessment suggests significant hydrogen cost reduction due to the improved energy efficiency, reduced material cost and simplified system, and by-product profits, demonstrating the scalability of the as-proposed SVE process.