Cobalt hydroxide catalyst advances ambient ammonia synthesis

A cobalt hydroxide catalyst produced ammonia at a record-reported rate of 40.67 μg h−1 cm−2, with 24.9% Faradaic efficiency, but the 180-hour result remains laboratory work rather than a plant-scale project.

The research team includes Qingdao Agricultural University in China, Politecnico di Milano in Italy and Trinity College Dublin in Ireland. Its paper appears in eScience under DOI 10.1016/j.esci.2025.100513, with a listed publication date of September 2026. The study targets a material with direct agricultural and energy uses: ammonia for fertilizer, with potential demand as a hydrogen carrier.

Why does ammonia need a different production route?

The incumbent process has scale and reliability on its side, along with substantial energy demands. Conventional Haber-Bosch production supplies nearly all global ammonia and operates at extreme heat and pressure.

• The process consumes about 1% to 2% of global energy.
• It releases roughly 1.6 tons of carbon dioxide per ton of ammonia produced.
• Electrocatalytic nitrogen reduction could instead use renewable electricity under ambient conditions.

The technical obstacle lies in atmospheric nitrogen. Its strong N≡N bond has a bond dissociation energy of 941 kJ/mol, which makes nitrogen activation exceptionally difficult.

Existing associative pathways also suffer from premature hydrazine release or high activation barriers. Those failures lead to poor selectivity and sluggish reaction kinetics. Researchers therefore seek mechanisms that lower energy barriers, suppress competing hydrogen evolution and enable practical ammonia synthesis without the Haber-Bosch conditions.

The catalyst has changed the laboratory reaction pathway, but it has not yet changed ammonia supply.

What did the team change in the catalyst?

The researchers call their mechanism hydroxide-activated hydrogen spillover, or HAHS. It depends on controlled lattice distortion within cobalt hydroxide, Co(OH)₂.

By adjusting the synthesis temperature, the team elongated Co-O bonds and weakened nearby O-H bonds. Hydrogen atoms from surface hydroxyl groups can then detach and participate directly in nitrogen reduction. Their departure creates surface hydrogen vacancies, which hydrogen species from the electrolyte continuously replenish.

That sequence produces a self-sustaining catalytic cycle. Unlike conventional associative pathways that require several proton-coupled electron-transfer steps, HAHS bypasses one elementary step. The mechanism accelerates intermediate turnover while suppressing the competing hydrogen evolution reaction.

In plain terms, the catalyst supplies some of the hydrogen needed for the reaction instead of treating that hydrogen only as a rival process.

What evidence supports the mechanism?

Density functional theory calculations put the initial activation of N₂ on Co(OH)₂ at almost no free-energy barrier, with ΔG = 0.01 eV. The catalyst also maintained its structural integrity through 180 hours of continuous operation.

Two analytical methods supplied experimental support:

• In situ electron spin resonance detected evidence associated with hydrogen spillover and vacancy formation.
• Isotope-labeled differential electrochemical mass spectrometry provided further direct evidence for the proposed mechanism.

The authors said: “the HAHS mechanism fundamentally changes how we think about nitrogen reduction.” They also explained: “instead of fighting against the competing hydrogen evolution reaction, their approach actually harnesses hydrogen from the catalyst itself to drive the reaction forward.”

The team said its lattice-distortion engineering provides atomic-level control over bond strengths. It also described the method as a new paradigm for electrocatalyst design that could extend beyond ammonia synthesis to other complex multistep reactions.

The measurements support the mechanism, though they do not establish commercial economics.

What could HAHS change in the ammonia market?

The researchers see a route to distributed, on-site ammonia production for fertilizer. Such plants could serve agricultural demand without replacing central ammonia facilities or their associated carbon emissions.

Ambient operation also fits renewable electricity systems. The proposed process uses nitrogen from air, water and electricity, while ammonia could serve as a carbon-free hydrogen carrier for energy storage and transportation.

The authors describe HAHS as a scalable and cost-effective strategy enabled by relatively simple lattice engineering. That claim stops short of a commercial demonstration. The study gives no named pilot site, plant capacity, capital cost, electricity price, ammonia production cost or construction timetable.

No regulatory approval pathway or permit deadline appears in the research either. The result therefore cannot be treated as an announced industrial project.

What milestone will decide what happens next?

The deciding market milestone will be a disclosed pilot or commercial project that tests whether the 40.67 μg h−1 cm−2 rate and 180-hour stability survive outside the laboratory. That program would need to report plant capacity, capital cost and the cost per ton of ammonia against commercial benchmarks.

Until those figures exist, HAHS remains a promising laboratory mechanism, not a new ammonia plant.