Seawater electrolysis sparks new hope for green hydrogen future

Posted on 02 January 2023

Researchers in China claim their technique bypasses the need for desalination

For years hydrogen has been considered the fuel of the future, viewed as a potential clean energy source for heating, industrial, agricultural and long-distance transport. 

One technique of harvesting hydrogen is via electrolysis, but according to Chemistry World, researchers in China have recently discovered a way to produce hydrogen by splitting seawater without the need to desalinate or purify it. Seawater makes up over 96% of the world’s water and could be a considerable step in the shift toward delivering a future of affordable green hydrogen.

Sustainable fuel researcher Alex Cowan at Liverpool University believes the project has potentially achieved something considered very challenging from a chemistry perspective. Cowan explains that the technology lies within a niche market that hasn’t been targeted before. Splitting water through electrolysis is relatively simple and has been completed in hydrogen facilities with access to the conventional water supply. The process that happens in an electrolyser involves electrically separating hydrogen from oxygen and enabling hydrogen to be acquired. With seawater, the process is more complex because salt and other impurities can damage the electrolyser. 

One option is to desalinate and purify seawater before processing, but it can be expensive. A secondary option is to treat electrolyser components to avoid corrosion. As an alternative, scientists at Shenzhen and Nanjing University have created another option. They separated the electrolyser from the seawater with a waterproof and breathable membrane.

Working effectively like a sieve, the membrane prevents anything other than pure water vapour from entering the electrolyser. As water vapour is drawn in and converted to hydrogen, more is added from the seawater to take its place. A study by Nature regarded this process as a self-sustaining system. Scientists introduced a test project in Shenzhen Bay, creating over 1mn litre of hydrogen over 133 days with no reports of degradation. 

Cowan explains that operating it for over 3,000 hours provides a baseline for stability. Cowan believes one possible application could be in offshore wind, powering seawater electrolysers with hydrogen moved back to land. Another concept is with the Gigastack project in the Humber estuary, where offshore wind is powering electrolysers, with hydrogen used at the Humber refinery.

Hydrogen currently accounts for approximately 2% of the global energy market but is experiencing a revival. The big challenges with hydrogen are scaling up hydrogen, reducing costs and lowering the carbon footprint. Existing electrolysers operate on a megawatt level, not a gigawatt level. The UK hydrogen strategy intends to double the target for low-carbon hydrogen output to 10GW by 2030. The target to green the hydrogen industry is driving new strategic plans worldwide. 

The Hydrogen Shot Initiative launched in the US last year aims to reduce the cost of green hydrogen to $1 per kg by 2030. As part of the hydrogen strategy, the EU has created a ten-year plan to develop new infrastructure, transport networks and fuelling stations. Europe hopes green hydrogen can replace natural gas in selected industries like steel production. More importantly, the price of renewables required to produce green hydrogen is decreasing. It may take several more years to see significant progress, but right now, a clean hydrogen future is looking more promising.

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