A team of researchers from the Department of Physics at IIT-Madras has developed a technology prototype to produce green hydrogen (GH2) from seawater in a simple and cost-effective manner. In a report on the approach, published in the journal ACS Applied Energy Materials, the researchers propose that the technology could support India in meet its green hydrogen target without putting pressure on fresh water, a scarce natural resource.
India’s National Green Hydrogen Mission, which aims to boost India’s green hydrogen production and ecosystem, has set a target to build capabilities for producing at least five Million Metric Tonnes (MMT) GH2 per annum by 2030. However, the government also recognises its impact on freshwater – one of the key inputs for GH2 production – so it is pushing to maximise industrial and municipal wastewater use for hydrogen production wherever feasible.
Green hydrogen is produced from pure water through a process known as electrolysis, which uses an electric current from renewable energy to split water into its component molecules, hydrogen and oxygen, using a device called an electrolyser. In effect, green hydrogen is “clean” as it has low carbon emissions and is expected to play a prominent role in decarbonising heavy industries, including oil refineries, steel mills and fertiliser plants. The traditional electrolysers, however, are designed to work with pure water, and scaling up the GH2 process could exacerbate global freshwater shortages.
The new technology and research from IIT Madras aims to tap into the abundantly available seawater directly to make GH2, which may reduce the sole demand on freshwater. The alternative electrolyser is currently at a prototype stage and could take some time before it is commercialised. Globally, while similar research is going on, commercialisation of prototypes is limited.
A two-megawatt electrolyser. Representative image. Photo by Bubble60/Wikimedia Commons.
A professor at the Department of Physics at IIT Madras, Sundara Ramaprabhu, who led the team of researchers for this invention, claimed that this invention addresses the twin challenges of water scarcity and cost optimisation. “We have indigenously developed alkaline water electrolyser, a critical component for a highly efficient, cost-effective way to electrolyse seawater,” he said while talking to Mongabay India.
The researchers used a carbon-based support material for the electrodes instead of metals to almost eliminate the possibility of corrosion.
Explaining further, Anamika Ghose and Sana Fathima, who are also part of the research team, said that the potential to generate hydrogen from seawater through electrolysis is hindered by issues related to chlorine corrosion and the slow rate of hydrogen evolution. These factors pose challenges that need to be addressed to improve the efficiency and effectiveness of seawater electrolysis for hydrogen production.
An assembled single-cell alkaline seawater electrolyser prototype, made at IIT Madras. Photo from IIT Madras.
Additionally, the researchers used transition metals like iron, copper etc. to create catalysts that could facilitate oxygen and hydrogen production. Transition metals are widely used in industrial applications like electronics, alloys and magnetic materials. Based on these innovations, researchers claim, “We can use the seawater just like normal water electrolyser to produce hydrogen and oxygen.”
India’s consumption of grey hydrogen, which is produced from natural gas using low-carbon methods, currently stands at six million tonnes. However, if India were to generate an equivalent amount of green hydrogen, it would necessitate approximately 132-192 million tonnes of water.
Globally, researchers are putting efforts into using seawater directly for GH2 production. There are two ways in which seawater can be used to replace fresh water for the production of GH2 – desalination of seawater to produce fresh water to remove the salt before the water flows to conventional electrolysers and the use of seawater directly for the electrolysis process.
As many green hydrogen projects are coming in water-scarce areas, nearly 85% of the green hydrogen capacity in the global pipeline may need to source its water from desalination, according to Rystad Energy, an independent research company. Oman, which has launched an ambitious green hydrogen programme, is also taking the desalination route and aims to produce at least one million tonnes of renewable hydrogen a year by 2030 using electrolysers powered by renewable electricity to extract hydrogen.
Deepak Yadav, Programme Lead, Council on Energy, Environment and Water (CEEW), says that desalination is a proven technology in which seawater is desalinated and demineralised. Then it is used for producing GH2.
Splitting seawater comes with its own set of problems. Most of the current projects use electrolysers powered by renewable electricity to extract hydrogen from desalinated seawater. However, desalination and purifying technologies are expensive to provide significant quantities of clean deionized water for efficient electrolysis.
According to UNEP, about 1.5 litres of liquid polluted with chlorine and copper are created for every litre of potable water produced through desalination. When pumped back into the ocean, the toxic brine depletes oxygen and impacts organisms along the food chain.
Though, the direct splitting of seawater provides an eco-friendly route for producing clean hydrogen. But corrosion of electrodes from saltwater hampers the mass production of GH2.
However, efforts are going at the global level to use seawater directly to make green hydrogen. China-based Dongfang Electric Corporation (DEC) successfully tested non-desalinated direct seawater electrolysis technology for hydrogen production powered by offshore wind on June 6, 2023.
Deepak Yadav from CEEW says that research is ongoing globally and in India, but it is at a lower technology readiness level (TRL) in terms of maturity. Technology readiness levels are a method for estimating technologies’ maturity. They are based on a scale from 1 to 9, with 9 being the most mature technology. “We need to move from TRL 3 to TRL 7 or 8 when we can start commercialising the technology. This technology might take a few years to see the light of day. And it is too early to comment on the techno-economics viability of the technology,” he adds.
A two-electrode mode setup for the lab-scale testing of catalysts for seawater splitting. Though, the direct splitting of seawater provides an eco-friendly route for producing clean hydrogen, the corrosion of electrodes from salt water is said to hamper the mass production of GH2. Photo from IIT Madras.
Ramaprabhu from IIT Madras echoes, “Globally, many technologies are being developed to produce hydrogen from seawater, but nobody has been able to reach industry level prototype level and commercialisation stage for producing hydrogen through seawater technology.”
He feels that the technology is promising and will soon be commercialised. “The technology is already at the industry level prototype stage and would take a maximum of six months for commercialisation as we are in an advanced stage of discussions with big industry players in the renewable technology space,” claims Ramaprabhu.
Ramaprabhu further claims that the technology developed by IIT Madras can be used with industrial and domestic wastewater. They are already planning to start experiments with industrial wastewater.
Original News Link
https://india.mongabay.com/2023/07/iit-madras-scientists-develop-techniques-to-use-seawater-for-green-hydrogen/
