# The Ethanol Oxidation Reaction Performance of Carbon-Supported PtRuRh Nanorods
## 3 Results and Discussion  
The exact compositions of PtRu, PtRh, and PtRuRh determined by SEM-EDS are displayed in Table S1. It seems that by the FAM process, carbon supported PtRu, PtRh, and PtRuRh catalysts can be prepared. The structural information of PtRu, PtRh, and PtRuRh catalysts obtained by XRD is shown in Figure S1. The peaks of XC-72R carbon black are located at 25\({}^{\circ}\) for all catalysts. For the Pt catalysts, peaks located at 39.80\({}^{\circ}\), 46.28\({}^{\circ}\) and 67.53\({}^{\circ}\) are attributed to the (111), (200) and (220) planes of face-centered cubic (fcc) Pt, respectively, (JCPDS 870646). For PtRu and PtRh, the characteristic peaks are located at 40.23\({}^{\circ}\), 46.70\({}^{\circ}\) and 68.03\({}^{\circ}\), which are obviously shifted to larger angle when compared to the Pt reference, owing to the smaller atomic radius of Ru (134 pm) and Rh (134 pm) than that of Pt (139 pm) and lattice shrinkage during alloying. In terms of the ternary catalysts, the peaks are located at 40.63\({}^{\circ}\), 47.07\({}^{\circ}\) and 68.40\({}^{\circ}\) for PtRuRh. The d-spacing calculation results are around 0.227, 0.224, 0.224, and 0.222 nm for Pt, PtRu, PtRh, and PtRuRh, respectively. The decrease in d-spacing in binary and ternary catalysts demonstrates that Ru and Rh atoms partially substitute Pt atoms in the structure. The calculated lattice parameters for catalysts are listed in Table S1, in which the prepared binary and ternary catalysts have the lattice parameter of 0.384 nm compared to 0.392 nm for Pt, related to the alloying and EOR enhancement [52]. The calculated mean grain sizes for Pt, PtRu, PtRh, and PtRuRh are 5.3, 4.6, 4.6, and 4.8 nm, respectively. Figure 1 presents the morphologies of Pt, PtRu, PtRh, and PtRuRh by HRTEM. From Figure 1a-d, it can be observed that various NRs can be successfully prepared by FAM, in which the mean aspect ratios of Pt, PtRu, PtRh, and PtRuR is 4.5 \(\pm\) 0.9, 4.7 \(\pm\) 0.9, 4.5 \(\pm\) 0.8, and 4.7 \(\pm\) 0.8, respectively. Figure 1e-h shows the morphologies after CA test, in which the mean aspect ratios of catalysts shorten into 2.1 \(\pm\) 0.7, 2.1 \(\pm\) 0.6, 1.8 \(\pm\) 0.6, and 2.0 \(\pm\) 0.7 for Pt, PtRu, PtRh, and PtRuRh, respectively, as summarized in Figure 1i-l, suggesting that during CA test, the catalysts suffer from dissolution, migration, corrosion, etc. Figure 1: High-resolution transmission electron microscopy (HRTEM) micrographs of morphologies before CA: (a) Pt (b) PtRu, (c) PtRh and (d) PtRuRh; after CA: (e) Pt, (f) PtRu, (g) PtRh and (h) PtRuRh; aspect ratios distributions: (i) Pt, (j) PtRu, (k) PtRh and (l) PtRuRh. The XPS spectra of Pt, PtRu, PtRh, and PtRuRh catalysts analyzed by XPS are displayed in Figure 2 and their surface compositions are listed in Table S2. In Figure 2, the Pt peaks located at 71.0 and 74.3 eV belong to 4f\({}_{72}\) and 4f\({}_{52}\), respectively. For other binary and ternary catalysts, slight shifts are noted due to different degrees of electron transfer between Pt and the second or third metals [53; 54]. Moreover, the addition of the second metals influences the chemical states of Pt in which the Pt oxide compositions increase or decrease owing to the Ru or Rh addition, respectively. Meanwhile, the amount of OCS, such as PtO\({}_{x}\), RuO\({}_{x}\), or RhO\({}_{x}\), is also influenced and the EOR performances are also affected. It has been reported that the presence of Ru can modify the surface electronic structure of Pt, causing the downshift of the Pt d-band center, weakening the interaction between Pt and absorbed intermediate species, and enhancing the EOR durability of Pt-based catalysts [55]. Therefore, such OCS plays an important role in determining the EOR performance. On the other side, the TPR experiments are carried out to analyze the topmost surface species of the catalysts.