How Acidic CO₂ Electrolysis Can Clean Up Heavy Industry

Most industrial CO₂ today leaves the stack at high pressure, hot, and often acidic. That’s not a bug of heavy industry – it’s how refineries, steel mills, and chemical plants actually run.

Here’s the thing about green technology: if it can’t plug into that messy reality, it stays in the lab. That’s why the latest work on CO₂ electroreduction in strong acid is such a big deal. It points to a way of turning industrial CO₂ into useful multi‑carbon products (like ethylene and ethanol) inside the process itself, instead of piping it away to be buried.

A recent electrochemistry study shows how surface‑adsorbed iodide ions on copper can dramatically boost the formation of multi‑carbon (C₂⁺) products from CO₂ in harsh acidic conditions. On the surface this sounds niche. In practice, it goes straight to one of the hardest problems in climate tech: how to decarbonize chemicals and fuels at gigatonne scale.

This matters because green technology won’t hit scale with solar panels and EVs alone. We also need electrochemical routes that turn CO₂ into chemicals using clean electricity – and those routes have to work where industry lives: high current, high pressure, often low pH.

Below, I’ll break down what’s actually interesting here, how iodide helps copper “like” CO₂ more than hydrogen in strong acid, and what this could mean for future CO₂‑to‑chemicals plants.

CO₂ electroreduction 101: why multi‑carbon products are the prize

The core idea of CO₂ electroreduction is simple: you run renewable electricity through an electrochemical cell and push CO₂ to become something more valuable – CO, formate, ethylene, ethanol, acetate, and so on.

From a climate and business perspective, multi‑carbon products (C₂⁺) are the sweet spot:

• Ethylene and ethanol are massive commodity chemicals.
• They integrate directly into existing petrochemical value chains.
• Their market prices can actually pay for capital and power, if you get efficiency and scale right.

Copper is currently the only practical metal that can make a broad mix of these C₂⁺ products at decent rates. That’s why most advanced research – including the work behind this post – keeps coming back to copper catalysts and how to control their surface structure and local environment.

There’s a catch, though.

Why acidic CO₂ electrolysis is hard (and why it’s worth solving)

Most high‑performing CO₂ electrolyzers today use alkaline or near‑neutral electrolytes. They work, but they bring some messy system‑level problems:

• Carbonate formation wastes CO₂ and complicates carbon balance.
• You need larger gas recycling loops and separation units.
• Integrating with industrial CO₂ streams (which are often acidic and compressed) is non‑trivial.

By contrast, acidic CO₂ electrolysis can, in principle, offer:

• Higher single‑pass CO₂ conversion (lab reports are approaching ~90%).
• Simpler integration with acid gas streams from existing plants.
• Better compatibility with proton‑exchange membranes and compact membrane electrode assemblies (MEAs).

The problem? In strong acid there are tons of protons, and they really want to grab electrons first. Instead of converting CO₂, your cell mostly makes hydrogen gas. Selective C₂⁺ formation almost disappears.

That’s the basic tension this new iodide‑on‑copper approach tries to resolve: how do you make copper prefer CO₂ coupling over hydrogen evolution in a sea of protons?

The iodide trick: teaching copper to behave in strong acid

The new research shows that surface‑adsorbed iodide ions (I⁻) on copper can flip the script in strong acid. They don’t just “sit there” as spectators. They reshape the local microenvironment at the interface where CO₂ reduction actually happens.

At a high level, iodide does three important things simultaneously:

1. Stabilizes a copper surface that’s good for C–C coupling
   Iodide has a strong affinity for copper oxides (like Cu₂O) and metallic Cu. It tends to anchor onto the surface and can guide the exposure of specific copper facets and active sites that favor CO and C₂ intermediates.

2. Modifies the electric field and hydration structure near the surface
   Anions and cations shape the electric double layer. Iodide is large and polarizable, so it can alter how water molecules and protons arrange themselves right at the interface. That, in turn, affects how easily CO₂ and CO adsorb and how likely two CO units are to couple into C₂ species.

3. Suppresses, or at least competes with, hydrogen evolution
   By crowding the surface and steering proton access to certain sites, iodide helps reduce the number of spots where straight hydrogen evolution reaction (HER) dominates. More of your electrons end up going into carbon chemistry.

The result is enhanced CO₂ electroreduction to multi‑carbon products in strong acid, at current densities and product distributions that start to look compatible with industrial aspirations.

If you zoom out from the specific paper, this fits into a broader trend in CO₂ electrochemistry over the past few years: stop thinking only about the metal; start engineering the entire microenvironment – cations, anions, hydration shells, local pH, and even hydrophobic pockets near the surface.

What’s special about multi‑carbon products in acidic conditions?

C₂⁺ formation on copper generally follows a sequence:

1. CO₂ is reduced to adsorbed CO (*CO).
2. Two CO‑derived species on neighboring sites couple (C–C coupling).
3. Further proton‑electron transfers turn these intermediates into ethylene, ethanol, acetate, and other products.

In alkaline media, a lot of work has gone into:

• Selecting the right copper facets (Cu(100), stepped sites, nanoparticles).
• Using alkali cations (K⁺, Cs⁺) to promote CO coverage and C–C coupling.
• Pairing CO₂‑to‑CO catalysts with Cu (tandem catalysis) to push C₂ yields.

In strong acid, though, the environment is much more hostile:

• Surface oxides and favorable copper structures can dissolve or restructure.
• Proton activity is high, so HER tends to dominate.
• The double‑layer structure is different; many tricks from alkaline systems don’t translate directly.

This is where iodide adsorption gets interesting:

• It can stabilize certain copper surface states even under acidic, reducing conditions.
• It influences the coverage and dynamics of CO intermediates.
• It coordinates with other electrolyte design strategies (like choice of cation) to sustain high C₂⁺ selectivity.

Conceptually, you’re moving from “What copper alloy should I build?” to “How do I program the interface so that electrons, CO₂, protons, and intermediates are all in the right place at the right time?”

Why this matters for real green technology, not just lab metrics

From a Green Technology and business perspective, this line of research supports three big shifts that I think are underrated.

1. From capture‑and‑bury to on‑site CO₂ upgrading

If acidic CO₂ electrolysis can be made robust, you can imagine:

• Bolt‑on electrochemical modules attached to flue gas lines.
• Direct conversion of purified (but still “industrial‑grade”) CO₂ into ethylene or ethanol.
• Integration with PEM‑style MEAs fed from renewable power.

Instead of paying to compress and ship CO₂ to a sequestration site, plants could:

• Turn CO₂ into revenue‑generating products.
• Reduce their net emissions footprint.
• Participate in low‑carbon product markets without completely rebuilding their infrastructure.

2. Electrolyzer designs that match how industry actually operates

Strong‑acid systems mesh well with proton‑exchange membranes and compact stacks – architectures that industry already understands from fuel cells and certain types of water electrolysers.

The iodide‑on‑copper concept slots into that world by offering:

• Higher current densities at a given cell footprint.
• Better C₂⁺ selectivity than you’d expect in damagingly acidic media.
• Potentially simpler carbon management, since you reduce carbonate formation and improve single‑pass conversion.

If you’re designing future green chemical plants, that’s attractive: smaller stacks, simpler balance of plant, fewer moving parts.

3. AI‑driven catalyst and electrolyte design

This blog series focuses on how AI powers clean energy and sustainable industry. Iodide‑modified copper in acid is a perfect example of where AI can – and already does – make a difference:

• High‑throughput DFT and machine‑learning models can scan thousands of anion/cation combinations to predict which will tune the double‑layer the right way.
• Surrogate models can quickly estimate how microenvironment tweaks affect CO coverage, C–C coupling barriers, and selectivity among ethylene, ethanol, and acetate.
• Reinforcement learning can guide experimental campaigns: which electrolyte composition, potential window, and flow conditions to test next for maximum C₂⁺ Faradaic efficiency.

I’ve found that the most successful teams in this field think of AI not as an add‑on, but as part of the design loop: theory → AI search → rapid experiments → updated models. Surface‑adsorbed iodide is one outcome of that mindset – and there’s no reason chloride, bromide, fluorinated species, or organic anions won’t follow similar paths.

What should companies and innovators actually do with this?

If you’re running or building a climate‑tech or industrial operation, here’s how to translate this science into strategy.

1. Start treating CO₂ as a feedstock, not a waste stream

Look at your process map and ask where:

• CO₂ leaves the plant at moderate or high pressure.
• You already operate with acidic streams or proton‑exchange equipment.

Those are your candidates for on‑site CO₂ upgrading using acidic electrolysis.

Even if the exact iodide‑on‑copper system from the paper isn’t off‑the‑shelf yet, you can:

• Model different product scenarios (ethylene vs ethanol vs acetate) against your existing utilities and offtake contracts.
• Quantify the value of converting 10–30% of your CO₂ stream in the near term.

2. Build literacy around electrochemical microenvironment design

Most companies are still wired to think in terms of “what catalyst metal should we pick?” The frontier is shifting to “what local environment do we need at the interface?”

Practically, that means:

• Hiring or training electrochemists who understand double‑layer physics, not just bulk catalysis.
• Investing in analytics that can probe the interface (in situ Raman, IR, X‑ray techniques) to see intermediates and surface states in real time.
• Partnering with labs or startups that treat electrolyte composition as a design space, not a constraint.

Once your team can think fluently about anion and cation effects, strategies like surface‑adsorbed iodide stop looking like exotic tricks and start looking like knobs you can systematically turn.

3. Use AI to shrink the search space

Electrolyte and catalyst‑microenvironment optimization is exactly the kind of high‑dimensional problem AI handles well.

If you’re serious about entering this space:

• Build or adopt materials‑informatics pipelines that combine first‑principles data with lab results.
• Let models propose candidate electrolyte recipes (e.g., specific iodide concentrations, mixed anion systems, tailored cation cocktails) that are most likely to boost C₂⁺ selectivity in your operating window.
• Treat the lab as a validation engine for AI‑generated hypotheses, not the other way around.

Companies that do this well will move faster than traditional trial‑and‑error R&D and will be better positioned to own IP around practical, scalable CO₂‑to‑chemicals platforms.

Where this fits in the bigger green technology picture

As we close out 2025, the climate conversation is finally shifting from “Can we hit net zero?” to “How do we retrofit heavy industry without shutting it down?” Electrochemical CO₂ conversion in strong acid, boosted by smart microenvironment design with species like iodide, is one of the more realistic paths on the table.

This line of work connects several threads we’ve covered in the Green Technology series:

• AI‑assisted discovery for clean energy materials.
• Electrification of chemical manufacturing using renewables.
• Smart, compact systems (like MEAs) that plug into existing plants instead of requiring greenfield builds.

If you’re planning your next move in climate tech or industrial decarbonization, the message is straightforward: don’t ignore CO₂ electrolysis in acid just because the textbook says “HER dominates.” The field is moving towards catalysts and electrolytes that make those textbooks outdated.

The question isn’t whether we can teach copper to behave better in harsh environments – iodide and similar strategies show that we can. The real question is: who’s going to be first to turn that capability into reliable, bankable plants that turn industrial CO₂ into valuable multi‑carbon products at scale?