A series of binary PtRu catalysts with different Pt/Ru atomic ratios (from 7:3 to 3:7) were synthesized on a carbon support using the colloidal method; they were then used for electrooxidation of glycerol in acid media. X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray absorption spectroscopy analyses were used to investigate particle size, size distribution, and structural and electronic properties of the prepared catalysts. Ru added to the Pt‐based catalysts caused structural and electronic modifications over the PtRu alloy catalyst formation. The electrocatalytic activities of PtRu/C series catalysts were investigated using cyclic voltammetry. The Pt5Ru5/C catalyst shows enhanced catalytic activity at least 40 % higher than that of the Pt/C catalyst, with improved stability for glycerol electrooxidation; these improvements are attributed to structural and electronic modifications of the Pt catalysts. Using an electrocatalytic batch reactor, product analysis after the oxidation reaction was performed by high‐performance liquid chromatography to determine and compare the reaction pathways on the Pt/C and PtRu/C catalysts. To understand different catalytic activities of glycerol oxidation on the PtRu alloy surfaces, density functional calculations were performed.

Single-atom catalysts (SACs) have emerged as promising materials in heterogeneous catalysis.P revious studies reported controversial results about the relative level in activity for SACs and nanoparticles (NPs). These works have focused on the effect of metal atom arrangement, without considering the oxidation state of the SACs.H ere,w e immobilized Pt single atoms on defective ceria and controlled the oxidation state of Pt SACs,f rom highly oxidized (Pt 0 : 16.6 at %) to highly metallic states (Pt 0 :8 3.8 at %). The Pt SACs with controlled oxidation states were then employed for oxidation of CO,C H 4 ,o rN O, and their activities compared with those of Pt NPs.T he highly oxidized Pt SACs presented poorer activities than Pt NPs,w hereas metallic Pt SACs showed higher activities.The Pt SACreduced at 300 8 8Cshowed the highest activity for all the oxidations. The Pt SACs with controlled oxidation states revealed ac rucial missing link between activity and SACs.

A few studies have claimed that Pt single‐atom catalysts (SACs) can catalyze the oxygen reduction reaction (ORR) following a four‐electron pathway (O2+4H++4e−→2H2O). Here, we show that, in the presence of a seemingly negligible amount of Pt nanoparticles, the ORR can mistakenly be thought to occur via a four‐electron pathway on Pt SACs. Various weight percentages (1, 2, 4, 8 wt%) of Pt SACs were prepared on C3N4 layers deposited on a carbon support (C@C3N4). Through a combination of H2/CO uptakes and high angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) results, the amount of Pt nanoparticles could be estimated when they were mixed with Pt single atoms. Particularly, most of Pt in the 4 wt% Pt catalyst existed as single atoms, but a small number of Pt nanoparticles co‐existed. Although this catalyst seemed to follow the four‐electron pathway, the reaction actually occurred on Pt nanoparticles, not Pt single‐atoms.