The UK engineers working to kickstart the hydrogen economy

Engineers across the UK are researching hydrogen’s role in decarbonising industry, exploring ammonia for greener steel and repurposing offshore assets for hydrogen transport. Adam Duckett caught up with three of them to ask what they expect to achieve and the engineering challenges they will need to overcome

MARK SYMES, professor of electrochemistry and electrochemical technology at the University of Glasgow, is researching whether it’s possible to develop an electrolyser that produces hydrogen directly from seawater. His work explores a novel type of electrolysis that could be safer, more tolerant of various water sources, and reduce compression requirements.

Symes is one of ten researchers awarded a share of £3m (US$3.7m) from the UK Hub for Research Challenges in Hydrogen and Alternative Liquid Fuels (UK HyRES), which is run out of the chemical engineering department at the University of Bath.

The hub was set up in 2023 to coordinate research that will accelerate the development of hydrogen technology that could help the UK meet its net zero goals. The R&D programme is divided into four technical themes: production; storage and distribution, use, and alternative liquid fuels. Symes’ research falls under the production banner.

“Decoupled electrolysis allows the user to make hydrogen and oxygen from water in different places, at different times, and at rates that are not connected,” Symes says.

“In a decoupled electrolyser, we have an electrochemical cell that produces oxygen at the anode, like a conventional electrolyser, but at the cathode we don’t make hydrogen. Instead, the electrons and protons from water oxidation are used to reduce and protonate a dissolved redox mediator.”

The mediator would then be removed and put in a reactor where it would be exposed to a catalyst to spontaneously release the hydrogen. The mediator could then be returned to the electrochemical cell to be used again.

“The safety and compression advantages come about as you make the hydrogen outside the electrochemical cell. So that means that the oxygen and hydrogen can never mix, which is great.

“It also means that you can design a hydrogen generation chamber to be optimised for high pressure hydrogen production, which is much harder to do if the hydrogen is made directly inside the electrolyser.

“Tolerance to different water feeds comes about as the electrochemical cell used in decoupled electrolysis has electrolyte solutions on both sides of the membrane, so any ions in the feedwater can move freely from one compartment, through the membrane, and into the other compartment. They don’t block the membrane like they would in, say, a proton exchange membrane cell.”

The team is investigating mediators that could do the job with seawater. If they can identify suitable candidates, they plan to produce them at kilogram scale and test them in a prototype device operated by Clyde Hydrogen Systems, which is already trying to develop a decoupled electrolyser that runs on freshwater. Producing hydrogen from seawater would be far more advantageous – there’s much more available – allowing production to occur on repurposed offshore oil and gas facilities or nearer wind farms during surplus energy generation.

Separate efforts are already underway investigating how technologies can be combined to produce hydrogen offshore. Among them is the Dolphyn Hydrogen project that was piloted off the UK last year. It involves a single platform equipped with a wind turbine to power a desalination unit, which produces freshwater for electrolysis, splitting it into hydrogen and oxygen.

On his team’s coming research priorities, Symes says: “There are a bunch of really knotty and really interesting chemical engineering challenges in the project. We need to fine-tune the anode potential so that we make oxygen and not chlorine. How will the flow rates of the anode and cathode liquid streams impact the current density that can be supported? How will the introduction of chloride and sodium affect the hydrogen release process and what hydrogen generation reactor designs or operation protocols will allow us to optimise the process for seawater? Will sodium and chloride accumulate in the mediator solution, to the extent that we need to develop processes for removing excess sodium chloride from the mediator solution?”

Getting hydrogen ashore

Alfonso Martinez-Felipe, senior lecturer in chemical engineering at the University of Aberdeen, is working out how to determine the feasibility of repurposing offshore assets for hydrogen production, generation, and storage. A key challenge with hydrogen is that it finds its way between metal atoms in pipes and weakens them – a process called embrittlement.  

“Our aim is to test if pipelines and other steel-based materials previously used in offshore assets can be used for long-range hydrogen transport,” Martinez-Felipe says.

The team are obtaining sample materials used in offshore platforms and pipelines to test their mechanical properties before and after hydrogen exposure.

“In parallel, we will design some hydrogen diffusivity tests through those samples, under different pressure and temperature conditions. The experimental results will help us build a model that informs about the feasibility of the materials, taking into account potential hydrogen embrittlement and structural damage.”

“We will correlate the feasibility of each material with its service-life conditions including its lifetime, environmental conditions, and the fluids that it has been exposed to.”

This will allow them to create a toolkit that industry could then use to understand which infrastructure can be reused for hydrogen transport.

“The information about the mechanical properties can also tell us whether they can be used to store hydrogen, and under which conditions,” he adds.

Ammonia for greener steel

Aidong Yang, professor of engineering science at the University of Oxford, is working out how ammonia might be used for the direct reduction of steel in a bid to reduce the carbon footprint of a sector responsible for 8% of global emissions.

“We will undertake experimental testing using lab-scale reactors, use the experimental data to inform the development of mathematical models and then carry out model-based analysis to assess the potential of these two direct-reduction schemes at an industrially relevant scale,” says Yang.

He hopes to identify the key factors that affect the performance of ammonia direct reduction in terms of product quality and energy efficiency, so they can determine how it compares to hydrogen direct reduction. If it proves favourable, then it could bolster plans to convert hydrogen to ammonia whose properties arguably make it safer for bulk transport as the hydrogen economy and global trading expands.

Conventionally, a key stage in steelmaking is using coal to reduce iron ore but research has already shown that this can be done with green hydrogen. Last year, an industrial consortium in Sweden declared their pilot tests were a success and that they would push ahead with commercialisation of the technique.

Yang said: “Compared to direct reduction by hydrogen, reduction by ammonia is much less well understood. This hinders the construction of a reliable mathematical model that is able to capture all the key process characteristics. We expect that much of the work in this project will be dedicated to the design and execution of ammonia direct reduction experiments to produce sufficient data that will inform both qualitative and quantitative understanding, to pave the way for mathematical modelling and model-based assessment.”

The ten awards follow 14 that were previously awarded by Bath’s HyRES initiative.

Commenting on the latest awards, HyRES project leader Tim Mays said: “This gives UK HyRES a comprehensive base of top-tier research expertise to help answer the key questions around how we can use hydrogen and zero-carbon alternative liquid fuels to help reach net zero.”