Stable PtAu alloy colloids with a wide range of compositions were prepared using pulsed laser ablation on single metal-mixture targets in water. The concentration of Pt in the alloys can be tuned by varying the Pt/Au ratio in the targets, which are made by compression molding a mixture of Pt and Au powders at different ratios. Such fabricated PtAu alloy nanoparticles (NPs) show a face-centered cubic structure, and their composition basically follows that of their corresponding targets. The effect of aqueous solution pH and ablating laser fluence on the formation and structure of alloy NPs was further investigated. It is found that PtAu alloy colloids of identical composition can be achieved over a pH range extending from 4.0 to 11.0 and at fluences varying from 4 to 150 J cm–2 as long as the targets of the same composition are used. This finding suggests that alloy formation is essentially insensitive to both factors in certain ranges, and the method developed herein for the alloy NP formation is quite robust. Moreover, the surface composition, estimated from electrochemical measurements, is identical to the overall composition of the NPs estimated from Vegard’s law and X-ray diffraction data, which is a strong indication of the uniform composition on the surface and in the interior of these alloy NPs.

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La 0.6 Sr 0.4 Fe 0.6 Mn 0.4 O 3−δ (LSFM) perovskite-type catalysts were prepared by a nanocasting route based on solution combustion synthesis, called the soft−hard templating (SHT) approach. Three silica hard templates with different textural properties were used to increase the specific surface area of the perovskites, and hence to improve their electrochemical activity for both oxygen evolution and reduction reactions. Careful structural and physicochemical characterization revealed that the materials are composites formed by crystalline LSFM perovskite and amorphous metal silicates, even after the etching procedure. Both the composites' specific surface area and the fraction of silicates are proportional to the silicas pore volume. Interestingly, the LSFM perovskite obtained by SHT has lower cell volumes than the parent oxide prepared without a silica template. The electrochemical characterization revealed the contrasting effects of the metal silicates on the performances of the electrodes. The LSFM-SHT-based electrodes have higher double-layer capacitance and higher current for oxygen evolution than those prepared with the parent LSFM. Furthermore, the LSFM-SHT-based electrodes show a preferential 4-electron pathway during the oxygen reduction reaction, if the amount of amorphous silicates is low (Si wt % < 3.5 wt %). However, the silicates also shift the onset potential of both oxygen evolution and reduction reactions to more positive and negative potential values, respectively, thus delaying the two reactions.