Electrochemical microscopy maps local thermochemical catalysis on platinum
Mar 6th 2026
A team used SECCM-EBSD to image electrochemical half-reactions on polycrystalline platinum at submicrometre scale, revealing grain-dependent activity, lateral galvanic coupling, and chemical cross-talk where formic acid-generated CO poisons suppress oxygen reduction while oxygen modestly aids formic acid oxidation.
- Researchers combined scanning electrochemical cell microscopy and electron backscatter diffraction to map formic acid oxidation and oxygen reduction on polycrystalline platinum with submicrometre resolution.
- Individual grains show distinct reactivity: some facets like Pt(112) and Pt(144) are among the most active overall while Pt(100) is relatively active for ORR but less so for FA oxidation.
- Overlaying isolated half-reaction voltammograms predicts a current equivalency potential, but the measured mixed potential during concurrent reactions is about 0.1 V lower, indicating co-reactant interactions.
- Tafel analysis at the mixed potential gives spatially resolved estimates of local thermochemical reaction rates that align with ensemble measurements at slower scan rates.
- The presence of formic acid strongly attenuates ORR across grains while oxygen slightly promotes FA oxidation, effects attributed to CO poisoning generated during FA oxidation.
- Results reveal lateral galvanic coupling between grains and chemical cross-talk between half-reactions, pointing to strategies such as spatial separation to reduce poisoning and boost catalytic rates.