With the global energy transformation, hydrogen energy will undoubtedly become one of the important energy sources in the future. The ocean is the largest hydrogen mine on Earth, and seeking water from the ocean is an important direction for future hydrogen energy development. However, the composition of seawater is very complex, containing over 90 chemical elements, as well as a large number of microorganisms and suspended particles, resulting in many technical bottlenecks and challenges such as harmful corrosiveness and toxicity, catalyst deactivation, and low electrolysis efficiency. For this reason, two different technology roadmaps of direct hydrogen production from seawater and indirect hydrogen production from seawater have been formed [
1]. Seawater indirect hydrogen production is essentially freshwater hydrogen production. Currently, large-scale demonstration projects have been conducted in many countries, such as the PosHYdon Offshore Green Hydrogen Pilot Project of Netherlands [
2], the Brande Hydrogen Wind Power Hydrogen Pilot Project of Siemens Gamesa [
3], and the Tracebel Overdick Offshore Wind Power Hydrogen Production Platform Project of Germany [
4]. However, this type of technology relies heavily on large-scale desalination equipment, with complex processes and occupying a large amount of land resources, further increasing the cost of hydrogen production and the difficulty of engineering construction. Since the concept of direct electrolysis of seawater for hydrogen production was proposed in the 1970s [
5], research teams from Stanford University [
6], Nanyang Technological University [
7], Dalian University of Technology [
8], Technical University of Berlin [
9] and others have performed a lot of exploration and research around catalyst engineering, membrane material science, etc. However, up to the present, there is still no breakthrough theory and principle to completely avoid the impact of complex components of seawater on the electrolytic hydrogen production system, which has become a global problem for nearly half a century.
In response to the above challenges, the team of Academician Heping Xie of Shenzhen University/Sichuan University created a new principle and technology of
in situ seawater direct electrolysis for hydrogen production by combining physical and mechanical processes such as molecular diffusion and interfacial phase equilibrium with electrochemical reaction, established a theoretical method of seawater direct electrolysis for hydrogen production driven by gas-liquid interface phase change self-migration, and formed a mechanical driving mechanism of seawater spontaneous phase change and mass transfer due to interfacial pressure differences. It has realized the dynamic self-adjusting and stable direct electrolysis of seawater for hydrogen production with electrochemical reaction and seawater migration without additional energy consumption, completely isolated all seawater ions, and realized large-scale and efficient
in situ direct electrolysis of seawater for hydrogen production without the desalination process, side reaction and additional energy consumption, perfectly solved the half-century problem in the field of seawater electrolysis for hydrogen production, and realized the direct use of inexhaustible seawater as pure water for hydrogen production by electrolysis. This achievement was published in
Nature on November 30, 2022 [
10].
Based on this new principle and technology, the team of Academician Heping Xie and Dongfang Electric Corporation in China jointly developed the world’s first offshore wind power non-desalination of seawater
in situ direct electrolysis hydrogen production platform—“Dongfu No. 1” (Fig.1), integrating
in situ hydrogen production, smart energy conversion management, safety detection control, loading and unloading lifting and other systems. The sea trial was successfully conducted in Xinghua Bay, Fuqing City, Fujian Province, China from May 17 to 26, 2023. The scale of hydrogen production in this sea trial reached 1.3 N∙m
3 (H
2)/h, which reached or exceeded the design value, with an energy consumption of electrolysis of 5 kWh/(N∙m
3) (H
2). After continuous and stable operation in a real marine environment for more than 240 h, the ion barrier rate of seawater impurities still reached over 99.99% (equivalent to the effect of direct electrolysis of pure water for hydrogen production), and the purity of hydrogen production reached 99.9%–99.99% (Fig.2) [
1]. This sea trial successfully verified the reliability of direct electrolysis of seawater for hydrogen production using offshore wind power without desalination in a real marine environment [
1].
The novel principle technology of this sea trial does not require the cost and engineering investment of seawater desalination process, seawater transportation process, and seawater pollution treatment process after desalination. With the further development of offshore wind power technology and the decrease in grid electricity prices in the future, the cost of direct hydrogen production from seawater is expected to be lower than that of coal to ash hydrogen production.
This successful sea trial fully marks a significant step forward in the industrialization process of direct electrolysis of seawater without desalination, and signifies the formal entry into a new era of direct electrolysis of seawater for hydrogen production.
Academician Heping Xie said that the next step will be to iteratively develop more efficient, more compatible, and more stable seawater direct electrolysis hydrogen production technology and equipment, and establish an industrialization alliance for global enterprises to comprehensively promote industrialization [
1]. It is expected that in the near future, the new industrial model integrating renewable energy such as offshore wind power and direct electrolysis of seawater to produce hydrogen will bring new breakthroughs and opportunities for the development of global marine energy and hydrogen energy industries.
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