## 3 Results  
### Characterization  
Figure 1 shows the FESEM micrographs of the RAWOS and RAWS catalysts. The RAWOS samples showed the presence of aggregated structures of RuO\({}_{\mathrm{x}}\) nanomaterials inside and on the surface of the \(\gamma\)-Al\({}_{2}\)O\({}_{\mathrm{3}}\) support. By contrast, the PEG-stabilized RAWS sample exhibited a finger-like protrusion of RuO\({}_{\mathrm{x}}\) on the surface of the \(\gamma\)-Al\({}_{2}\)O\({}_{\mathrm{3}}\). The TEM image of RAWOS sample (Figure 2a) clearly displayed the distinction between \(\gamma\)-Al\({}_{2}\)O\({}_{\mathrm{3}}\) (gray) and small size RuO\({}_{\mathrm{x}}\) (black) which is non-uniform in shape and size. EDX analysis was also performed in the above locations, which confirmed the particular morphological feature was due to RuO\({}_{\mathrm{x}}\). At the same time, RAWS clearly showed the presence of rod-like structures with a length and width of _ca._ 200 and 75 nm, respectively (Figure 2b). Assemblies of nanorods like this were widespread throughout catalyst samples. The approximate elemental composition measured by EDX for the corresponding catalysts can be seen in the right side of the figures. The RAWOS catalyst contains 58.34% oxygen and 9.78% Ru, whereas RAWS contains 46.49% oxygen and 50.94% Ru (atomic percentage). The observed one dimensional (1D) growth found in RAWS is proposed to originate from the formation of micelles in PEG solution, which further directs the growth of the catalyst. As noted previously in the literature, the formation of 1D structure is achieved due to the effect of PEG acting as a capping and growth directing agent. The ordered chain structure of PEG (mainly arising from oxygen in the C-O-C chains) is anticipated to adsorb easily on a ruthenium-rich surface, coordinating with the ruthenium ions, forming PEG-Ru\({}^{+3}\) complexes in the colloidal state and confining growth at specific crystal faces [32,33]. Subsequent neutralization with alkaline solution (ammonia) produces PEG-Ru(OH)\({}_{\mathrm{3}}\). Finally heat treatment at high temperature (650 \({}^{\circ}\)C) removes PEG and water which results in the ruthenium oxide nanomaterials. This process is shown schematically in Figure 3.  
Figure 1: The FESEM surface morphological images of RAWOS (**a**) and RAWS; (**b**) catalysts. (Abbreviations: RAWOS: RuOx/\(\gamma\)-Al2O3 without polymer stabilizer; RAWS: PEG stabilized RuOx/\(\gamma\)-Al2O3). Figure 2: The TEM images of (**a**) RAWOS and (**b**) RAWS catalysts, and the EDX spectra of (**c**) RAWOS and (**d**) RAWS catalysts along with the elemental composition. The phase and crystal structure of the ALVIR, RAWOS and RAWS catalysts were analyzed by using XRD and given in Figure S1. The diffraction pattern of the as-received alumina shows prominent diffraction peaks at 2\(\theta\) = 36.7, 45.8 and 66.9\({}^{\circ}\) corresponding to the (311), (400) and (440) reflections of \(\gamma\)-Al\({}_{2}\)O\({}_{3}\), respectively (_cf._ JCPDS card no. 00-010-0425). Commonly, commercial \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) is mesoporous with a higher surface area and is the most thermodynamically stable phase of alumina [34, 35, 36]. The XRD diffractograms of both the synthesized and heat-treated catalyst materials displayed identical peaks although reflections corresponding to RuOx could not be observed clearly, which may due to the inclusion of Ru atoms in the interstitial sites of alumina or it may simply due to the lesser amount of RuOx (1 wt.%) [37]. In case of the X-ray diffractometer employed in this work, it was found that the catalyst loading should be greater than 7 wt.% to clearly identify RuOx diffraction peaks and to calculate the lattice parameters. The FTIR spectra of the ALVIR, RAWOS and RAWS catalysts are shown in Figure S2a-c, respectively. As-received alumina exhibited prominent bands at 550 cm\({}^{-1}\) and 790 cm\({}^{-1}\) corresponding to the Al ions in octahedral and tetrahedral surrounding (Al-O vibrations), respectively [38].