Process could help cut carbon emissions in the steel industry

University of Oregon chemists are bringing a greener way to make iron metal for steel production closer to reality, a step towards cleaning up an industry that’s one of the biggest contributors to carbon emissions worldwide. The research was published in ACS Energy Letters.

Last year, UO chemist Paul Kempler and his team reported a way to create iron with electrochemistry, using a series of chemical reactions that turn saltwater and iron oxide into pure iron metal.

In their latest work, they’ve optimized the starting materials for the process, identifying which kinds of iron oxides will make the chemical reactions the most cost-effective. That’s a key to making the process work at an industrial scale.

“We actually have a chemical principle, a sort of guiding design rule, that will teach us how to identify low-cost iron oxides that we could use in these reactors,” Kempler said.

Used in everything from buildings to cars to infrastructure, almost 2 billion metric tons of steel were produced worldwide in 2024. Currently, the most fossil fuel-intensive part of that process is turning iron ore—the oxidized form of iron that’s found in nature—into pure iron metal.

Traditionally done in blast furnaces that send carbon dioxide into the atmosphere, Kempler’s team is developing a different approach to iron production.

Their process starts with saltwater and iron oxide, which are cheap and available, and transforms them into iron metal through a series of chemical reactions. Those reactions conveniently also produce chlorine, a commercially valuable byproduct.

When Kempler and his team began developing their process a few years ago, they started with small quantities of iron oxides from chemical supply companies.

Those materials worked well in lab tests. But they didn’t reflect the kind of iron-rich materials found naturally, which have much more variation in composition and structure.

“So then a very natural next question was: What happens if you actually try to work with something which was dug out from the earth directly, without being extra purified, extra milled, and so on?” said Ana Konovalova, who co-led the project as a postdoctoral researcher in Kempler’s lab.

As the team experimented with different kinds of iron oxides, it was clear that some worked much better than others. But the researchers weren’t sure what was driving the difference in the amount of iron metal they could generate from different starting materials. Was it the size of the iron oxide particles? The composition of the material? The presence or absence of specific impurities?

Konovalova and graduate student Andrew Goldman found creative ways to test certain variables while keeping others the same.

For example, they took iron oxide powder and made it into nanoparticles. They put some of the nanoparticles through a heat treatment that made them much denser and less porous.

“It solidifies into this same secondary nanoparticle shape, but there are no more primary particles observed inside. It’s essentially the same material, just in different stages,” Konovalova said.

In lab tests, the difference was striking: “With the really porous particles, we can make iron really quickly on a small area,” Goldman said. “The dense particles just can’t achieve the same rate, so we’re limited in how much iron we can make per square meter of electrodes.”

That’s a key insight for making the process work at an industrial scale, where success often comes down to economics.

Large-scale electrochemical plants are expensive to build, and that cost scales with electrode area. To make it economically viable, the electrodes need to be able to generate enough product quickly enough to pay off the initial investment.

The faster rate of reaction of the porous particles means the initial capital cost can be recouped faster, translating into a lower final cost for the iron product, ideally low enough to be competitive with conventional methods.

The takeaway isn’t that these specific nanoparticles are needed to make the electrochemical process work well, Kempler said. Rather, the study suggests that the surface area of the starting materials really matters. The porous nanoparticles had much more surface area for the reaction to take place, making the reaction run faster. Other iron oxides with a porous structure could also be cost-effective.

“The goal is to find something that’s abundant, cheap and that’s going to have a smaller environmental impact than the alternative,” Kempler said. “We won’t be satisfied if we invent something that’s more damaging than the main way that we make iron today.”

To take their process beyond the lab, Kempler’s lab is working with researchers in other fields. A collaboration with civil engineers at Oregon State University is helping them better understand what’s needed for the product to work in real-world applications. And a collaboration with an electrode manufacturing company is helping them address the logistical and scientific challenges of scaling up an electrochemical process.

“I think what this work shows is that technology can meet the needs of an industrial society without being environmentally devastating,” Goldman said.

“We haven’t solved all the problems yet, of course, but I think it’s an example that serves as a nucleation point for a different way of thinking about what solutions look like. We can continue to have industry and technology and medicine, and we can do it in a way that’s clean—and that’s awesome.”