Yejun Park

Iron-phosphate∕platinum∕carbon nanocomposites for enhanced electrocatalytic stability

The effects of FePO4–Pt∕C nanocomposites on the electrocatalytic properties were examined after 1000 accelerated cycles (up to 1.48V vs normal hydrogen electrode). The FePO4–Pt∕C nanocomposites exhibited similar electrocatalytic properties to Pt∕C without any initial degradation, and also showed enhanced long-term stabilities. By optimizing the synthetic conditions of FePO4–Pt∕C nanocomposites, the well-dispersed FePO4 nanoparticles played important roles in preserving the Pt surface activities, by preventing both the dissolution and agglomeration of Pt nanoparticles.

Nanostructured Platinum/Iron Phosphate Thin-Film Electrodes for Methanol Oxidation

Nanostructured Pt-FePO 4 thin-film electrodes consisting of Pt nanocrystals and amorphous FePO 4 were fabricated by cosputtering, and nanocomposites containing ∼3 or ∼5 nm Pt crystalline phases were obtained. Compared with the pure Pt electrodes, the Pt-FePO 4 electrodes containing ∼3 nm Pt nanophases showed a significantly high efficiency, stability, and low charge-transfer resistance for methanol oxidation. The improved catalytic activities of the Pt-FePO 4 thin-film electrodes can be attributed to both an increase in the active surface area, and the possible ability of FePO 4 for the effective transfer of protons and the CO oxidation during methanol oxidation.

Nanostructural Effect of AlPO4-Nanoparticle Coating on the Cycle-Life Performance in LiCoO2 Thin Films

To control the nanostructure of an AlPO 4 -coating layer, nanoparticles with three AlPO 4 phases were synthesized: amorphous, tridymite, and cristobalite phases. These colloids were layered on LiCoO 2 thin films by spin coating, and subsequently annealed at 400°C. The interdiffusion variations at the interface were eliminated by the spin-coating method, while the cycle-life performance of the coated cathode depended on the nanostructure of the AlP04-nanoparticle-coating layer. The LiCoO 2 thin-film cathode coated with amorphous nanoparticles and annealed at 400°C showed the best cycle-life performance, and effectively suppressed the degradation of Li + -diffusion kinetics during cycling.

Effects of iron-phosphate coating on Ru dissolution in the PtRu thin-film electrodes

The effects of FePO4 nanoscale coating on PtRu thin films were investigated on the block of Ru crossover. Ru dissolution was examined by the accelerated-potential cycles between 0.4 and 1.05 V. The results showed that Ru dissolution from FePO4-coated PtRu surface was inevitable due to the direct contact between the PtRu surface and aqueous electrolyte. However, the FePO4 coating layer on PtRu thin-film electrodes effectively retained the dissolved Ru species, thus preventing the dissolved Ru species from diffusing into the electrolyte. Moreover, the retained Ru species within the FePO4-coating layer were redeposited onto the PtRu surface during the cycling in the fresh electrolyte.