Carefully designing platinum catalysts on the atomic scale maximizes their performance in fuel cells.
Study: Maximize the Electrocatalytic Activity of Pt Toward Ethanol Oxidation via Engineering PdPt1 Single-Atom Alloy Skin. Image Credit: inter reality/Shutterstock.com
A team of materials scientists has demonstrated how atomic-scale design can dramatically improve the performance of platinum catalysts used in direct ethanol fuel cells. Writing in Advanced Materials, the researchers report a catalyst that maximizes the efficiency of platinum by isolating individual Pt atoms within a strained palladium surface, resulting in record activity while simultaneously cutting catalyst poisoning under alkaline conditions.
The study shows how combining single-atom alloys with strain engineering can overcome several persistant imitations in ethanol oxidation, a reaction central to ethanol-based fuel cells.
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Ethanol is an attractive fuel: Renewable, relatively safe, and energy dense. But oxidizing ethanol efficiently at a fuel-cell anode is tricky, involving multiple electron-transfer steps, breaking strong carbon-carbon bonds, and managing reactive intermediates such as carbon monoxide that readily poison platinum surfaces.
Platinum remains the most active known catalyst for ethanol oxidation, however, its efficiency is low. Many Pt atoms in conventional nanoparticles are either inaccessible or are quickly deactivated, making it difficult to use the metal economically or sustainably.
Single-Atom Platinum Surface
To address these issues, the team engineered a catalyst in which platinum atoms are used one by one.
Their approach begins with octahedral palladium-bismuth (PdBi) intermetallic nanocrystals, synthesized using a wet-chemical method. Isolated surface bismuth atoms then serve as anchoring sites for platinum through a galvanic replacement reaction, producing atomically dispersed Pt on the PdBi surface.
A subsequent electrochemical dealloying step removes surface bismuth and triggers a phase transformation, yielding a Pd5Bi3 intermetallic core surrounded by an ultrathin, tensile-strained face-centered-cubic palladium shell. During this process, the anchored Pt atoms are incorporated into the Pd shell, forming a PdPt1 single-atom alloy 'skin' in which each platinum atom is isolated and coordinated by surrounding palladium atoms.
Advanced microscopy and spectroscopy (HAADF-STEM, EELS, EXAFS, and XRD) confirmed both the atomic dispersion of platinum and the presence of tensile strain in the palladium lattice.
Recod Activity With Reduced Poisoning
Electrochemical testing revealed that the PdPt1 single-atom alloy skin exhibits exceptional performance for ethanol oxidation in alkaline media. When normalized by noble-metal mass, the catalyst outperformed commercial Pt/C, Pd/C, and dealloyed Pd catalysts, achieving a record platinum mass activity of more than 550 A mg-1.
Crucially, the researchers found that isolated platinum atoms are intrinsically more active than platinum clusters or Pt-rich surface layers. Adjusting platinum loading showed that the single-atom configuration maximizes platinum utilization rather than simply increasing metal content.
Durability tests further highlighted the catalyst’s advantages. After 12 hours of continuous operation at high potential, the catalyst retained more than 75 % of its initial current, while conventional Pt/C rapidly deactivated. CO-stripping and in situ infrared spectroscopy showed strongly suppressed carbon monoxide adsorption, explaining the improved stability.
What Happens To The Ethanol?
Product analysis using in situ FTIR spectroscopy, proton NMR, and carbonate titration revealed that the reaction proceeds primarily through the C2 pathway, producing acetate with a Faradaic efficiency of about 83 %. At the same time, measurable C-C bond cleavage occurs, generating CO2 and carbonate species through the C1 pathway.
Compared with conventional platinum catalysts, the PdPt1 surface shows enhanced activation of C–C bonds while still favoring selective oxidation to acetate rather than full conversion to CO2.
Strain And Single Atoms
Density functional theory calculations helped explain the observed performance. Tensile strain in the palladium lattice, combined with electronic coupling between Pd and isolated Pt atoms, broadens the metal d-band and increases the density of states near the Fermi level.
These changes strengthen ethanol adsorption, enable electron transfer, and lower the energy barriers for key dehydrogenation steps along the C2 pathway. The calculations also show a reduced activation barrier for breaking the C-C bond in the *CH2CO intermediate - still the most demanding step, but significantly easier than on unmodified palladium surfaces.
In combination, the results show that strain and atomic isolation work together to reshape reaction energetics without eliminating all kinetic limitations.
Implications For Fuel Cell Design
The study establishes the PdPt1 single-atom alloy skin as a highly active, durable, and poison-resistant electrocatalyst for ethanol oxidation in alkaline media. By fully exposing platinum atoms within an optimized electronic environment, the design achieves exceptional performance with minimal precious metal content.
While the work does not claim universal applicability, it offers a compelling framework for developing atom-efficient catalysts where alkaline operation is feasible, extending beyond ethanol oxidation to other electrochemical energy-conversion reactions.
Journal Reference
Chen, W., et al. (2026). Maximize the Electrocatalytic Activity of Pt Toward Ethanol Oxidation via Engineering PdPt1 Single-Atom Alloy Skin. Advanced Materials, e19429. DOI: 10.1002/ADMA.202519429.
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