Tuning oxygen reduction reaction activity via structure orientation and surface arrangement: A study on ordered PtCo/C catalysts

Impact of Heat Treatment on the Oxygen Reduction Reaction Performance of PtCo/C(N) Electrocatalyst in PEM Fuel Cell

“…The corresponding ORR Tafel plots were obtained in the interval of 0.85~0.95 V (Figure 5d), and the PtCo/C(N) catalysts obtained at different annealing temperatures were only Tafel slope of PtCo/C(N)-900 °C in the low current density region is larger than that of Pt/C-TKK, and the smaller the slope, the smaller the voltage required to vary the same current, the faster the ORR kinetics, and the better the ORR performance. [46,57] The impedance diagrams of the catalysts after annealing at different temperatures were tested by EIS (Figure 6), in which the first half (semicircular area) represents the charge transfer impedance, and the size of the diameter represents the magnitude of the impedance (the specific value was obtained according to the Z-view fitting), [58] and there is not a big difference in charge impedance of the catalysts treated with the four annealing temperatures in the HF region, and the largest is the value of the impedance of catalysts after annealing at 600 °C of 19.95 Ω, and the impedance value after annealing at 700 °C and 800 °C is 16.74 Ω, indicating that the catalysts prepared when the annealing temperatures are 700 °C and 800 °C have the highest electron transport efficiency. In the lowfrequency region, the slope of the PtCo/C(N)-900 °C catalyst is lower than that of the other three catalysts, which indicates that its mass transfer impedance is larger, and the remaining three catalysts are closer.…”

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

“…Notably, resembling X-ray photoelectron spectroscopy (XPS), XRD peaks can also be differentiated ,, and simulated, , providing basic help to distinguish conjoint facets or even phases. XRD patterns of nanocrystals with different synthetic conditions, most commonly, different annealing temperatures, are succinct and powerful when illustrating the phase-transformation process from alloy to intermetallics so as to extrude the key condition/temperature, therefore, are most universally applied as ordered-phase proof at first glance. ,,,, Furthermore, information about extra lattice strain and average grain size can also be obtained from XRD patterns by the relevant facet peak shifting and half-peak width. The former may paralleled with Rietveld refining, contribute to provide fuller structural sketch of heteroatoms or vacancies-doped/substituted intermetallics about their unit cell parameters, atomic site and occupancy, microstrain, etc., yet the latter may companied by size distribution analysis and help to evaluate the influence of size effect. , …”

“…One of the advantages that intermetallic catalysts have over their alloy counterparts lie in their enhanced capacity to influence the d -band/electronic structure. ,,, Despite various attractive shapes that have been realized on alloy nanocrystals, the developments of nanomaterial fabrication techniques also contributes to more and more fancy intermetallic compounds with increasingly smaller average sizes, ,,,,,− much more complicated composition, ,,,,− and tailored nanoscale morphology ,,,,− (as discussed in section and ). In contrast to the rather random atomic arrangement in disordered alloy structure, alternated distribution in intermetallics realizes sufficient interaction between different atomic species.…”

“…Moreover, many studies have displayed rather stable CV curves of Pt-based intermetallic nanoparticles, in which the shapes of characteristic peaks of specific facets remain indeformable even after long-life ADT, implying certain facet stability of intermetallics (scheme c). ,, Although the origin of such strong facet maintenance remains unknown, it may relate to the lower surface energy coming from ordered nature and condensed Pt layer. Thanks to the intrinsic pros in maintaining both SA and ECSA, intermetallics possess superior ORR stability, even under harsh conditions in MEA.…”

Design principles for the synthesis of platinum–cobalt intermetallic nanoparticles for electrocatalytic applications

“…The metal precursors are impregnated onto the mesoporous carbon, and the mixture is dried either by heat treatment or freeze drying. 78,94,95…”