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The following article was originally written by Manjeera Gowravaram and published here.

Combining hydrogen-based processes with advanced catalysts and renewable energy paves the way for developing economically and industrially viable solutions to decarbonise the steel industry

Globally, steel is a vital component of modern infrastructure and economic progress. India is among the top producers of steel. However, steel production is closely linked to environmental concerns as it relies heavily on coal as a fuel. In the steel production process, carbon (primarily sourced from coal and natural gas) reacts with iron ore to produce molten iron, which is then refined to create steel. However, this process also generates vast amounts of carbon dioxide (CO₂) but it also generates vast amounts of carbon dioxide (CO2). As a result, the steel industry globally emits over 3.7 billion metric tons of CO2 every year, contributing to 7–9% of carbon emissions. Steel production can be made sustainable by adopting a method called hydrogen-based direct reduction of iron (H-DRI).

In a recent review published in the Journal of Energy and Climate Change, researchers from the Chemistry Department at the Indian Institute of Technology Bombay (IIT Bombay), led by Prof. Arnab Dutta, have collated the advances made in the field of hydrogen generation for the steel industry and put forward the best way to decarbonise the steel industry using ‘green’ hydrogen.

The H-DRI process uses hydrogen to convert iron ore into steel instead of coal, releasing water vapour rather than carbon dioxide as a byproduct during the manufacturing process. This makes hydrogen a great option for “decarbonising” the steel industry. Currently, most of the hydrogen comes from processes like steam methane reforming or coal gasification. Both rely on fossil fuels, which still generate CO2, defeating the primary purpose.

So, to produce hydrogen sustainably, researchers are shifting towards water electrolysis — a process of splitting water into hydrogen and oxygen using electricity in an electrolyser device. If renewable energy sources like wind or solar can power the electricity, the process becomes emission-free, hence the term ‘green hydrogen’. However, producing green hydrogen at an industrial scale is expensive as it needs considerable infrastructure modifications and effective catalysts.

Catalysts are essential to make the water electrolysis used for hydrogen production effective. Generally, noble metals such as platinum and palladium are used as catalysts. “These (noble metals) are expensive and limit large-scale applications, and are not suitable for harsh or remote conditions,” says Dr. Suhana Karim, a postdoctoral research fellow in Prof. Dutta’s lab. “So, the focus is on finding alternatives that are economically viable and sustainable,” she adds.

Researchers worldwide, including Prof. Dutta’s group, are developing cobalt-based catalysts (cobaloximes) that are water soluble and air-stable to aid electrolysis without requiring specialised equipment. Cobaloximes are cheaper than noble metals and can be synthesised easily.

Several researchers have improved the stability and reaction rates of cobaloximes by modifying their molecular structure. For example, Prof. Dutta and his team have added natural amino acids, vitamins, and other functional groups into the catalyst’s structure to increase hydrogen production rates while maintaining energy efficiency. “We have also modified cobaloximes to work effectively in the presence of various minerals and salts, such as in seawater,” adds Dr. Suhana.

Cobaloximes work well in labs, but it is complex to use them for industrial hydrogen production. Hence, researchers are modifying their structure to make it compatible with the electrodes of the electrolyser and attaching them to solid supports to enhance stability, efficiency, and durability.

The researchers also analysed different types of electrolysers and furnaces to improve hydrogen production using renewable energy for industry. They found that cobaloxime catalysts perform well in both alkaline electrolysers, using solutions like potassium hydroxide, and proton exchange membrane electrolysers, which use a solid polymer membrane in acidic conditions.

“Each type has strengths and weaknesses in cost, durability, and efficiency,” explains Prof. Dutta.

In an electrolyser, when an electric current is passed through water, it splits, and hydrogen gets collected at the negative electrode (cathode) and oxygen at the positive electrode (anode). A complete set of electrodes, including a membrane, called a “stack”, separates the hydrogen and oxygen generation during electrocatalysis. Using multiple stacks, the electrolysers work more efficiently to produce copious amounts of hydrogen and can cut CO2 emissions by 30–50%, making the hydrogen-based energy economy more sustainable. “A single stack might produce one litre of hydrogen per day, but an appropriately designed multi-stack system can produce ten times as much using the same control setup,” explains Prof. Dutta.

Prototype of a Multi-Stack Electrolyzer Developed by Prof. Arnab Dutta’s Research Group.
Image Credits: Arnab Dutta And Suhana Karim

Researchers from IIT Bombay also point out that the traditional blast furnace-basic oxygen furnace method uses a lot of coal to produce steel, releasing a significant amount of CO₂. In contrast, the electric arc furnace uses electricity, and when powered by renewable energy, it produces less carbon emissions. Researchers believe that by combining hydrogen-based direct reduction of iron with electric arc furnace technology, steelmaking can become nearly carbon-neutral.

The use of green hydrogen can further be combined with carbon capture, utilisation, and storage (CCUS) strategies to further reduce emissions. CCUS systems capture any leftover CO₂ from steelmaking or other processes, allowing its use to produce synthetic fuels or chemicals or stored deep underground for the long term. This approach also promotes a circular economy by reusing CO₂ in productive ways.

The IIT Bombay study highlights how water electrolysis using cobalt-based catalysts, and
choosing suitable electrolysers and furnace types, can produce green hydrogen-based steel. This approach helps significantly reduce carbon emissions, paving the way for a cleaner and more sustainable future for steel production.

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The original academic article titled Cobalt-Based Molecular Electrocatalyst-Mediated Green Hydrogen Generation: A Potential Pathway For Decarbonising Steel Industry was written by IIT Bombay’s researchers and published in the journal, Energy and Climate Change, Volume 5.

The original paper can be found here.