On November 30, Professor Xie Heping, a Chinese mechanics and energy engineering scientist, along with Shenzhen University and Sichuan University’s doctoral team under his supervision, published a paper entitled “A Membrane-based seawater electrolyser for hydrogen generation” in Nature, which radically addresses the electrochemical saline water electrolysis problems. The study established new principle and technology for direct electrolysis of hydrogen without desalination combining physical mechanics and electrochemistry for the first time, which isolates seawater icons and reaching high-efficient direct seawater splitting technology breakthrough without additional energy input and side-reaction(that is, seawater is used as pure water, and in-situ electrolysis hydrogen is directly produced in seawater). The study has cracked the half-century problem of direct saline water electrolysis hydrogen production and is expected to form the Chinese “Ocean Green Hydrogen” emerging strategic industry.

As Nature Reviewers' comments, “Fewer paper can convincingly achieve large-scale and stable hydrogen production from seawater, but Team Xie‘s work does exactly this. They perfectly solved the corrosion problems and will open the door to low-cost fuel production and hopefully drive transition towards a more sustainable world."

Green zero-carbon hydrogen is an important direction of energy development in the future. It is estimated that by 2060, the annual demand for hydrogen in China will reach 130 million tons, and about 1.17 billion tons of pure water for electrolysis will be consumed each year. But a shortage of fresh water resources has seriously restricted the development of “green hydrogen” technology. The ocean is the largest hydrogen mine on earth, and hydrogen production from seawater will be an important development direction, which faced many difficulties and challenges because of complex seawater components (about 92 chemical elements). Desalination before hydrogen production is the most mature technical route for seawater hydrogen production at present, and large-scale demonstration projects have been carried out in many countries around the world. However this technology relies heavily on large-scale desalination equipment, together with the complex process and large amount of land resources increases the overall cost of hydrogen production and engineering difficulties. In the early 1970s, scientists considered direct saline water electrolysis hydrogen production and scientists around the world has been exploring but without breakthrough theory nor principle to completely eliminate the influence of seawater complex components.

Professor Xie Heping puts forward a new idea of combining physical mechanics and electrochemistry to solve the problems and challenges faced by direct electrolysis of seawater for hydrogen production, creatively creating a new principle and technology for in-situ direct electrolysis of hydrogen without desalination of seawater. By ingeniously combining physical and mechanical processes such as molecular diffusion and interfacial phase equilibrium with electrochemical reactions, a theoretical model of direct electrolytic hydrogen production from seawater driven by phase change migration was established, revealing the influence of interfacial pressure difference on the spontaneous phase transition of seawater under micron-scale air gap pathways. The influence mechanism of mass transfer has formed a dynamic self-regulating and stable electrolytic hydrogen production method with electrochemical reaction and seawater migration, which solved the half-century problem of harmful corrosion in the field of seawater electrolytic hydrogen production (patents applied for: CN2021110197054; CN114481164A; CN2022110704439; CN2022110748884; PCT/CN2022/128225).

Nature Reviewers of the study given high rating:“This work provides an attractive strategy, which allows non-potable water used for social and ecological sustainable fuel production, I think it’s a major breakthrough!”

Electrochemical saline water electrolysis using renewable energy as input is a highly desirable and sustainable method for the mass production of green hydrogen; however, its practical viability is seriously challenged by insufficient durability because of the electrode side reactions and corrosion issues arising from the complex components of seawater. Although catalyst engineering using polyanion coatings to suppress corrosion by chloride ions or creating highly selective electrocatalysts has been extensively exploited with modest success, it is still far from satisfactory for practical applications. Indirect seawater splitting by using a pre-desalination process can avoid side-reaction and corrosion problems, but it requires additional energy input, making it economically less attractive. In addition, the independent bulky desalination system makes seawater electrolysis systems less flexible in terms of size. Here we propose a direct seawater electrolysis method for hydrogen production that radically addresses the side-reaction and corrosion problems. A demonstration system was stably operated at a current density of 250 milliamperes per square centimetre for over 3,200 hours under practical application conditions without failure. This strategy realizes efficient, size-flexible and scalable direct seawater electrolysis in a way similar to freshwater splitting without a notable increase in operation cost, and has high potential for practical application. Importantly, this configuration and mechanism promises further applications in simultaneous water-based effluent treatment and resource recovery and hydrogen generation in one step.

Phase transition shift driven seawater without fade in situ direct electrolytic hydrogen production principles

Sea no fade in situ direct electrolytic hydrogen production scale of the equipment and stability