In this study the performance enhancement effect of structural ordering for the oxygen reduction reaction (ORR) is systematically studied. Two samples of PtCu3 nanoparticles embedded on a graphitic carbon support are carefully prepared with identical initial composition, particle dispersion and size distribution, yet with different degrees of structural ordering. Thus we can eliminate all coinciding effects and unambiguously relate the improved activity of the ORR and more importantly the enhanced stability to the ordered nanostructure. Interestingly, the electrochemically induced morphological changes are common to both ordered and disordered samples. The observed effect could have a groundbreaking impact on the future directions in the rational design of active and stable platinum alloyed ORR catalysts.

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Gradual, yet a great leap: electrosynthesized surfactant-stabilized gold atomic clusters (AuACs; Au(n) , 5≤n≤13) electrocatalyze the oxygen reduction reaction (ORR) in acid solution at low overpotentials. Depending on the surfactant concentration, the ORR mechanism gradually transits from a direct four-electron to a two-electron pathway (see picture; SHE=standard hydrogen electrode), which suggests the transformation of atomic clusters into nanoparticles.

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Crystalline Cu3Pt nanoparticles supported on graphitized carbon are synthesized by using a modified sol–gel method, and subsequent thermal annealing leads to alloying of Pt with Cu and formation of a partially ordered Pm${\bar 3}$m structure. Electrochemical dealloying under potentiodynamic conditions (potential cycling) induces not only changes from rather spherical high‐index faceted to more cuboctahedral low‐index faceted core–shell structures for particles in a size range of 10–20 nm but also percolation for some particles larger than 20 nm. In contrast, during dealloying under potentiostatic conditions (potential hold) the semispherical shape of small particles is completely retained and extensive porosity is formed on all particles larger than 20 nm. Other degradation processes are not observed on performing an additional accelerated aging test; hence, the high specific and mass activity of the catalyst decreases only slightly, mainly owing to continuing Cu leaching. The difference in dealloying protocols and their effect on the structure of the catalysts as well as their activities, considering the promising porosity formation, are discussed and indicate future directions for a rational design of active and stable oxygen reduction reaction catalysts.

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