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This paper shows how bubbling the reaction medium with CO affects the nucleation/growth of Pt nanoparticles under the synthesis using formic acid or formaldehyde as reducing agents. CO has been found to affect not only the dynamics of the Pt(IV) to Pt x 0 transformation but also the size of the formed particles (1.1–3.9 nm) deposited on the carbon support (ca. 20 wt% Pt). The dual role of CO due to combining the functions of a stabilizer and a reducing agent has been shown. The study demonstrates that the introduction of the dispersed carbon support to the reaction medium leads to the enhancement of the CO positive effect on the microstructure of Pt/C catalysts. In this case, the spatial distribution of Pt nanoparticles over the carbon support surface becomes more uniform that is conducive to increasing the electrochemical surface area. Thus, CO is a unique reagent used to control the microstructure of Pt nanoparticles during their wet synthesis.

This review considers the features of the catalysts with different nanoparticle structures architecture transformation under the various pre-treatment types. Based on the results of the publications analysis, it can be concluded that the chemical or electrochemical activation of bimetallic catalysts has a significant effect on their composition, microstructure, and catalytic activity in the oxygen reduction reaction. The stage of electrochemical activation is recommended for use as a mandatory catalyst pre-treatment to obtain highly active de-alloyed materials. The literature is studied, which covers possible variants of the structural modification under the influence of thermal treatment under different processing conditions. Additionally, based on the literature data analysis, recommendations are given for the thermal treatment of catalysts alloyed with various d-metals.