Pore diameter flips ORR from kinetic to transport control
Narrower Pt–Ni nanozyme channels raise ORR activity at low overpotential by concentrating protons, but at high overpotential O2 reacts at the pore mouth.
Source
The importance of nanoscale confinement to electrocatalytic performance
Study at a glance
- Design
- Animal / in-vitro — Pt–Ni nanozyme ORR with passivated exteriors plus Poisson–Nernst–Planck modelling of confined channels
- N
- Three etch-ratio channel-size distributions measured versus electrolyte concentration
- Population
- Platinum–nickel nanoparticles with isolated substrate channels
- Outcome
- Narrower confined channels raise ORR activity at low overpotential by concentrating protons; mass transport favors larger pores at high overpotential
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
Pore diameter flips ORR from kinetic to transport control
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Specific activity for the ORR was 3.3 times higher at 0.95 V when only channels were active.
Due to the use of oleylamine as the capping agent, the electrocatalytic reaction only proceeded within the substrate channels with the specific activity for the ORR being 3.3 times higher at 0.95 V (RHE) than when the surface outside the channels was exposed.
What does oleylamine do on these nanozymes?
the electrocatalytic reaction only proceeded within the substrate channels with the specific activity for the ORR being 3.3 times higher at 0.95 V (RHE)
What they did
Authors etched Pt–Ni particles with different channel-size distributions, passivated exteriors with oleylamine, measured ORR vs electrolyte concentration, and modelled EDL overlap and O2 depletion.
What they found
69/52/34% of channels <2 nm across three etch ratios. Specific activity 3.3× higher at 0.95 V when only interiors are active. Kinetic regime favors smaller pores; mass-transport regime favors larger pores. EDL ~3, 1, 0.33 nm at 0.01/0.1/1 M HClO4.
The limits
What it doesn't show
Active-site chemical identity inside vs outside is not independently proven; model assumes protons as the confined reactant.
Key terms
- Nanozyme (here)
- Nanoparticle with isolated substrate channels mimicking an enzyme active-site geometry.
- Nanoconfinement
- Altered concentrations/EDL when a pore is comparable to the double-layer thickness.
- Koutecký–Levich
- Analysis that extracts kinetic current by extrapolating to infinite rotation rate.
- EDL overlap
- When electrical double layers from opposite pore walls meet, changing ion profiles.
- Mass-transport limit
- Rate set by O2 diffusion, here localized at the channel entrance.
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Quiz yourself
Smaller channels help most when:
Common questions
When does smaller pore help?
Under kinetic control (low overpotential).
When does larger pore help?
Under O2 mass-transport control (high overpotential).
Why protons?
They migrate in as counter-ions and are also the ORR reactant.
Why oleylamine?
Passivates the exterior so only channels react.
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