2.1. Preparation of porous silica templates

Mesoporous silica SBA-15 was prepared using a previously reported method [4], which was further adopted as the template for preparing mesoporous CMK-3. First, tetraethyl orthosilicate (TEOS; 2.3 g, 399.0%, Aldrich), the silica source, was added to an aqueous solution containing HCl (8.0 g, 37% HCl in 30.0 g H₂O) and a triblock copolymer surfactant (1.0 g, P123; Acros) at 313 K. Second, the solution was aged at 373 K for 2 days after stirring for 2 h. Third, the suspension powder was filtered, washed, and dried. Finally, the product was calcined in air at 833 K for 6 h to remove the P123 soft template.

2.2. Preparation of mesoporous carbon CMK-3

The mesoporous CMK-3 adopted in this study was synthesized via a replication/carbonization process using SBA-15 as the hard template, referring to previously reported techniques [23]. First, the calcined SBA-15 was impregnated with a sucrose/H₂SO₄/H₂O solution in a weight ratio of 1:1.25:0.14:5 (SBA-15/ sucrose/H₂SO₄/H₂O). Second, the mixture was carbonized at 373 K (6 h) and 433 K (6 h). The above procedures were repeated prior to subjecting the sample to graphitization by pyrolysis at 1173 K for 1 h in an Ar environment. Finally, the mesoporous CMK-3 was obtained by removing the SBA-15 template by washing with a solution of 15% HF at 303 K.

2.3. Preparation of Pt–RuO_u–SnO_v/CMK-3 porous catalysts

The mesoporous catalysts, Pt–RuO_u–SnO_v/CMK-3 (where the subscripts u and v represent oxygen ratios in ruthenium and tin oxides, respectively), were prepared by referring to our previously reported reduction processes [4, 6, 7]. To obtain nominal metal loading, a mixture of metal chlorides including H₂PtCl₆⋅6H₂O (99.9%, Acros), RuCl₃ (99.9%, Acros), and SnCl₄⋅5H₂O (99.9%, Acros), in appropriate amounts depending on the desired catalyst composition, was dissolved in acetone and mixed with CMK-3. A uniform dispersion of the metal chlorides in CMK-3 was obtained by grinding the blend until the acetone evaporated, which yielded a uniform dispersion of the metal chlorides in CMK-3. Finally, the mesoporous catalysts were reduced in an H₂ environment in an oven at 200 °C for 6 h. The resulting composites of Pt, RuO_u, SnO_v, and CMK-3 were designated P_wR_xS_y/C3, where the subscript numbers w, x, and y represent the designated mass fractions of Pt, Ru, and Sn, respectively.

2.4. Physicochemical characterization

X-ray diffraction (XRD) powder patterns for the synthesized electrocatalysts were obtained on a PANalytical X’Pert Pro X-ray diffractometer using a Cu Kα source (𝜆 = 0.1541 nm). The microstructure and surface morphology of specimens were observed using transmission electron microscopy (TEM; JEOL JEM 2100F; accelerating voltage of 200 kV) and scanning electron microscopy (SEM, JSM-7100F). The mass fraction of each composition in mesoporous P_wR_xS_y/C3 catalysts was analyzed by an energy dispersive X-ray spectrometer. The textural properties (i.e., SSA and pore size dispersion (PSD)) of the samples were determined by Brunauer–Emmett–Teller (BET) N₂ adsorption–desorption isotherms using a Quantachrome Autosorb-1 analyzer. The samples were degassed at 473 K for ⩾12 h under vacuum followed by N₂ adsorption–desorption experiments conducted at 77 K. X-ray photoelectron spectroscopy (XPS) characterization was carried out with a Physical Electronics PHI 5600 multi-technique system using an Al monochromatic X-ray source at a power of 350 W.

2.5. Electrochemical characterization of P_wR_xS_y/ C3 electrocatalysts

Cyclic voltammetry (CV) and chronoamperometry (CA) experiments were carried out to characterize MOR in a three-electrode glass cell with a CHI 6273E galvanostat/potentiostat. The counter electrode and reference electrode were Pt wire and Ag/AgCl, respectively. The glassy carbon thin-film working electrode was prepared by subjecting a mixture of the Pt-loaded electrocatalyst sample (10 mg) in deionized water (5 mL) to ultrasonication for 30 min. A 20 μL aliquot of the catalyst dispersion was drawn and injected into the glassy carbon electrode (diameter ∼5 mm). The electrode was then dried in air at 333 K for 1 h. Finally, a 1% Nafion solution (20 μL, DuPont) was added to cover the electrode. A mixed solution of 1 M CH₃OH and 0.5 M H₂SO₄ was adopted as the electrolyte for the MOR experiments. Prior to each CV and CA measurement, N₂ (99.99%) was purged for 30 min to deoxygenate all solutions. Cyclic voltammograms were recorded in 0.5 M H₂SO₄ between 0.2 and 1.0 V at a scan rate of 10 mV/s.

3.1. Microstructure examination

Figure 1a depicts the low-angle XRD patterns of the as-prepared mesoporous silica SBA-15, CMK-3, P₂₀R₀S₀/C3, P₂₀R₀S₃₀/C3, P₂₀R₁₀S₀/C3, and P₂₀R₁₀S₁₅/C3 porous catalysts. Silica SBA-15 exhibits three small-angle peaks, which are characteristic of hexagonal ordered structures [23]. On the other hand, feature peaks at (1 0 0), (1 1 0), and (2 0 0) indicate a highly ordered periodic arrangement of mesoporous symmetry CMK-3, the replica of SBA-15 [24]. In addition, all P₂₀R_xS_y/C3 catalysts exhibit (1 0 0) diffraction peaks, corresponding to ordered mesoporous CMK-3, indicating that the hexagonally ordered mesostructure was maintained in all the synthesized samples.

Figure 1b shows the corresponding wide-angle XRD results of the following P₂₀R_xS_y/C3 samples: P₂₀R₀S₀/C3, P₂₀R₀S₃₀/C3, P₂₀R₁₀S₀/C3, and P₂₀R₁₀S₁₅/C3. As can be clearly seen, all the samples exhibit the typical characteristics of a face centered cubic crystalline platinum structure. The samples exhibit diffraction peaks at 2θ = 39.9°, 46.3°, 67.7°, and 81.6°, corresponding to the (111), (200), (220), and (311) diffraction planes, respectively. Compared with the XRD pattern of the P₂₀R₀S₀/C3 catalyst, the intensities of the (200), (220), and (311) planes of the P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3 catalysts are indiscernible; the broadened peaks could be attributed to their nanosize. As seen in Figure 1b, as the Sn content increases, the intensities of the Pt₂₀Ru₀Sn_y and Pt₂₀Ru₁₀Sn_y composite planes become significantly reduced and the peaks in the XRD patterns for the Pt(111) planes are broadened accordingly. Indeed, the Pt crystalline features diminish compared to the diffraction peaks of the P₂₀R₀S₀/C3 sample. The XRD peaks around 2θ = 25°, 34°, and 52° in Pt₂₀R₀S₃₀/C3 and P₂₀R₁₀S₁₅/C3 belong to the (110), (101), and (211) diffraction lines of tetragonal SnO₂, respectively [6], indicating the presence of SnO₂ in the catalysts. The average crystal size (ACS) (Table 1) in all the P₂₀R₀S_y/C3 (y = 0–40) and P₂₀R₁₀S_y (y = 0–20) catalysts was calculated by Scherrer’s equation tabulated in our previous report [25]. It is believed that the intrinsic stability of the SnO₂ crystal helps to prevent Pt-based composites from agglomeration during sample preparation. Therefore, it is reasonable that the ACS decreased as the Sn content increased.

Figures 2a and 2c illustrate the N₂ adsorption–desorption isotherms and the corresponding pore size distribution curves (Figures 2b and 2d) calculated from the isotherm adsorption branch by the Barrett–Joyner–Halenda (BJH) method for the P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3 catalysts. The N₂ adsorption–desorption isotherm of CMK-3 is close to type IV with an H1-type hysteresis loop, but the capillary condensation step is well defined. The ordered mesoporous carbon material CMK-3 has a much larger surface area than the Pt-loaded samples, where the decrease in surface area is mainly attributed to the average density increment caused by the heavy metals (i.e., Pt, Ru, and Sn). As shown in Table 1, the SSAs declined generally according to the percentage of metal. For example, P₂₀R₀S₀/C3 contains 80% of CMK-3 and thus the SSA_P20R0S0/C3 is approximately 80% of SSA_CMK-3. Figures 2b and 2d also show that the PSDs of all the catalysts are essentially identical. Overall, these results demonstrate clearly that our process maintains the CMK-3 mesostructure even at high Pt/Ru/Sn loadings.

Figure 3 shows typical high-resolution TEM (HRTEM) images of the CMK-3, P₂₀R₀S₃₀/C3, and P₂₀R₁₀S₁₅/C3. TEM images confirm that CMK-3 is a highly ordered mesostructure that exhibits an inverse replica structure of the SBA-15 template (Figure 3(a) side view and (inset) cross-section view). The images also clearly show that Pt–SnO₂ NPs are well dispersed on CMK-3 with discernible internal pore structures (Figure 3(b)). Further, after the dispersion of Pt–RuO_u–SnO₂ NPs on the carbon material support, all the NPs are uniformly distributed inside the pores of CMK-3 without noticeable aggregation (Figure 3(c)). Based on these observations, it can be determined that the average particle size of ∼3–5 nm of the metal alloy NPs is consistent with that calculated from Scherrer’s equation (Table 1). The low- and high-magnification SEM images of the Pt-loaded CMK-3 catalysts are shown in Figure 4. All the samples exhibit a similar configuration and pore size with CMK-3, indicating that the morphology was maintained during the carbonization step and the subsequent removal of the silica SBA-15 template without any significant modification or alteration, even at high metallic loadings. Nanoparticle dispersion can be clearly observed from the high-magnification image of the P₂₀R₁₀S₁₅/C3 sample (Figure 3c). The good dispersion of the metal NPs is conducive to avoiding particle agglomeration and maintaining a high active surface area of the composite [26]. The presence of metal elements on the porous CMK-3 framework was revealed by EDS elemental mapping (Figure 5), which indicates the desired amount of metals. Besides, they also confirmed that metallic components such as Pt, Sn, and Ru were dispersed uniformly on the mesoporous carbon CMK-3 for the P₂₀R₀S_y/C3 and P₂₀R_xS_y/C3 catalysts.

Thermogravimetric weight loss analyses of the P₂₀R₀S_y/C3 and P₂₀R_xS_y/C3 catalysts recorded by TGA experiments under an air atmosphere are shown in Supplementary Figures S1a and S1b, respectively. The maximum weight loss of pristine CMK-3 occurred at approximately 600 °C, whereas the maximum weight loss of the P₂₀R₀S_y/C3 and P₂₀R_xS_y/C3 catalysts occurred between 350 °C and 450 °C. These results suggest that the Pt–Ru–SnO₂ NPs are active and can potentially accelerate the oxidation reaction. As shown in the insets of Supplementary Figures S1a and S1b, the residue after the decomposition of carbon (CMK-3) was found to be in the range of 19–48 wt% for P₂₀R₀S_y/C3 and 28–51 wt% for P₂₀R₁₀S_y/C3 as the Sn content increased, respectively. The residual weight percentage approximately represents the total weight of Pt, Ru, and Sn, which is consistent with the EDS mapping results.

3.2. Effect of Sn ratio on catalyst chemical states

XPS was used to examine the chemical states of the elements, their contents, and valence states. Figure 6 shows the XPS Pt 4f peaks of the Pt₂₀/C3 catalyst. Deconvolution of the Pt 4f XPS doublet (4f_7/2 and 4f_5/2) gives rise to two pairs of peaks, corresponding to dominant Pt⁰ atoms and a smaller number of surface Pt(II) ions, respectively. The principal peaks with lower binding energies at 71.4 eV (4f_7/2) and 75.1 eV (4f_5/2) can be attributed to zero-valence Pt (Pt⁰), and the deconvoluted peaks at 72.2 and 76.0 eV and at 74.0 and 77.5 eV can be assigned to Pt in the 2⁺ and 4⁺ oxidation states, respectively [27]. The Pt peak found in its zero-valence state and that found in its ionic form are most commonly assigned as Pt(OH)₂ and PtO₂ and/or Pt–O–Sn phases [28, 29, 30]. Figure 7 shows the XPS Pt 4f peaks of the P₂₀R₀S_y/C3 (Sn wt% = 0, 10, 20, 30) and P₂₀R₁₀S_y/C3 (Sn wt% = 0, 10, 15, 20) catalysts. It is clear that the overall Pt peak shifts slightly toward lower binding energy following the inclusion of Sn NPs, that is, as the “y” values increase in P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3. This shift also suggests that alloying Pt with Sn can alter the electronic structure of Pt due to lattice strain and charge transfer [31]. As seen in Figure 7, increasing the Sn content tends to reduce Pt from an oxidized state to a metallic state in both P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3. This result is consistent with Zhou’s suggestion, by which the interaction between Pt and the SnO₂ NPs may prevent Pt surface oxidation, which leads to Pt–O bonds. Moreover, the result suggests that Pt can be more efficiently utilized by increasing the Sn content in both P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3. In short, the XPS results suggest higher catalytic activity may be achieved with a higher Sn content in the catalyst.

The chemical states of Sn in the catalyst were also examined by XPS, as shown in Figures 8 and 9. Figure 8 shows the XPS Sn 3d peak deconvolution peaks of the P₂₀R₀S_y/C3 (Sn wt% = 10, 15, 20, 30) catalysts. The Sn 3d spectra clearly exhibit intense doublets attributable to 3d_3/2 (494.7 eV) and 3d_5/2 (486.4 eV), indicating the presence of Sn⁴⁺ in SnO₂ [32, 33, 34]. It is clear that the metal state of tin (Sn⁰) only appears in P₂₀R₀S₁₀/C3. A further increase in the Sn content would lead to a greater amount of SnO₂, which is consistent with our expectation on account of previously reported XRD patterns [6]. Further, the XPS studies on the P₂₀R₁₀S₁₀/C3 catalysts also agree with this finding.

Figure 9 shows the XPS wide spectra with binding energies between 480 and 500 eV, where the Ru 3p_1/2 spectrum overlaps with Sn 3d_3/2 and Sn 3d_5/2 spectra. Since the binding energies of Sn⁰, Ru⁰, RuO₂, and RuO₂⋅zH₂O (z represents the molar ratio of hydrate) overlap within this range, it is exceedingly challenging to distinguish them accurately. For an easy comparison, however, the pair of sharp peaks at 486 and 495 eV can be attributed to SnO₂, and a pair of broad peaks is designated to represent the mixture of Sn⁰, Ru⁰, RuO₂, and RuO₂⋅zH₂O, as shown in Figure 9a. Except for the major SnO₂ phase, mixed phases are also present in the P₂₀R₁₀S₁₀/C3 catalyst. Additionally, the aforementioned mixed phases decrease as the Sn content increases from 10 to 20, as shown in Figures 9a–c. In other words, the decreasing tendency for the presence of Sn⁰ in P₂₀R₁₀S_y/C3 coincides with that in P₂₀R₀S_y/C3.

The effect of the Sn content may also influence the chemical state of Ru. To this end, Ru 3p_3/2 XPS analyses were also performed for the P₂₀R₁₀S_y/C3 catalysts (Figure 10). It is clear that RuO₂ is the major phase in P₂₀R₁₀S₀/C3, and Ru⁰ and RuO₂⋅zH₂O phases are equivalent. The addition of 10 wt% Sn decreases both the RuO₂⋅zH₂O and RuO₂ phases while Ru⁰ becomes the major phase. This is reasonable given that the standard reduction potential of Ru is greater than that of Sn. Further, the addition of 15 wt% and 20 wt% Sn did not show obvious effects on the Ru⁰/RuO₂⋅zH₂O/RuO₂ ratio. Ruthenium oxide and hydrated ruthenium oxide are considered to be the most effective choice for generating OH groups, which lead to best CO tolerance [35, 36]. Therefore, the addition of Sn may negate the positive effect of Ru on CO tolerance (vide infra).

3.3. Effect of Sn ratio on MOR mass activity and CO tolerance

Figure 11a shows the CV curves of the P₂₀R₀S_y/C3, and Figure 11b shows the CV curves of the P₂₀R_xS_y/C3 and commercial 30 wt% Pt/XC-72 samples in an acidic methanol medium (0.5 M H₂SO₄ and 1 M CH₃OH). Here, the effects of the Sn content on the catalytic activities of both P₂₀R₀S_y/C3 (y = 0–40 wt%) and P₂₀R₁₀S_y/C3 (y = 0–20 wt%) were investigated for the MOR. All the CV curves exhibit two representative oxidation peaks, denoting the forward oxidation current (I_f) ∼ 0.6 V and the backward oxidation current (I_b) ∼ 0.4 V. The I_f arises from the oxidation of methanol on the catalyst NP surface, during which a large number of oxygen-containing species such as CO₂ and CO are produced. The I_b value can be attributed to the further oxidation and removal of incompletely oxidized carbonaceous species (e.g., CO) [7]. These current values (I_f and I_b) and the I_f∕I_b ratio are significantly influenced by the Sn wt%, as depicted in Table 1. Overall, the I_f increased following the addition of Sn to both the P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3 systems. These results suggest that Pt–SnO₂ NPs provide more MOR active sites than pure Pt particles. The P₂₀R₀S₃₀/C3 and P₂₀R₁₀Sn₁₅/C3 catalysts with 30 wt% and 15 wt% Sn are the optimized conditions for the P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3 systems, respectively. Increasing the Sn wt% further leads to a slight decline in the I_f value for both systems. These trends match the variation in the ACS calculated by Scherrer’s equation, suggesting that the MOR activities of P₂₀R₀S_y/C3 and P₂₀R_xS_y/C3 depend greatly on the SSA of the alloy NPs. Besides, the optimized P₂₀R₁₀S_y/C3 demonstrates higher MOR activity than commercial 30 wt% Pt/XC-72, indicating that P₂₀R₁₀S_y/C3 is a competitive electrocatalyst.

On increasing the Sn content, clear increases in the I_f∕I_b ratio were observed for both types of catalysts. For the P₂₀R₀S_y/C3 catalysts, the I_f∕I_b ratio increased dramatically from 1.6 to 2.3 following the addition of 10 wt% Sn. Increasing the amount of Sn further to 15, 20, and 30 wt% led to only a slight increase in the ratio (to 2.5, 2.6, and 2.5, respectively). Notably, these observations are consistent with a bifunctional mechanism [37]. It has also been reported that the electronegativity difference induced by the Sn content may contribute to weaker absorption of carbonaceous intermediates on the Pt alloy surface [12]. Zhou et al. suggested that SnO₂ may generate more OH groups, leading to more effective oxidation of chemisorbed CO at the Pt–SnO₂ interface [38]. For the P₂₀R_xS_y/C3 catalysts, the P₂₀R₁₀S₀/C3 catalyst exhibits the largest I_f∕I_b ratio achieved in our study. The addition of 10 wt% Sn decreased the I_f∕I_b ratio from 2.8 to 1.9. Further increasing the amount of Sn to 15 wt% (i.e., P₂₀R₁₀S₁₅/C3) increased the I_f∕I_b ratio to 2.7, which is almost identical to the analogous value for P₂₀R₁₀S₀/C3. As a result, both P₂₀R₀S_y/C3 and P₂₀R₁₀S_y/C3 catalysts demonstrate outstanding performance for both the MOR activity and CO tolerance. In short, these results suggest that Sn can potentially be used to replace Ru in Pt-based catalysts in order to improve the MOR activity.

Although the I_f∕I_b ratio clearly increased following the addition of Sn (e.g., P₁₀R₀S_y/C3), the I_b values also increased slightly, suggesting that more CO species were adsorbed and that CO tolerance improved. However, it was previously reported that the co-addition of Ru can further augment the performance of Pt alloys [39]. Thus, three-metal Pt–RuO₂–SnO₂ composite catalysts have also been examined as P₂₀R₁₀S_y/C3 catalysts in this study. The results show an obvious increase in I_b and I_f∕I_b as the Sn content increases. The I_f∕I_b ratio of P₂₀R₁₀S₁₅/C3 (∼2.7) is second only to that of P₂₀R₁₀S₀/C3 (∼2.8), and it is a great improvement over that of P₂₀R₀S₀/C3 (∼1.6). In short, the MOR activities of both the two-metal P₂₀R₀S_y/C3 and three-metal P₂₀R_xS_y/C3 alloys, as evidenced by their I_f values, have been improved by the addition of an optimal amount of Sn. In addition, their CO tolerance, as evidenced by the I_f∕I_b ratio, is almost identical to that of P₂₀R₁₀S₀/C3. As predicted, however, the addition of Sn did eliminate the positive effect of Ru on CO tolerance (vide supra); thus, Pt₂₀Ru₁₀/C3 still shows the highest I_f∕I_b ratio observed in this study.

3.4. Effect of Sn ratio on long-term stability and cyclic durability

The long-term stability of our proposed mesoporous catalysts Pt₂₀Ru_xSn_y and commercial 30 wt% Pt/XC-72 was examined by chronoamperometric measurements at a forward peak potential of 0.7 V for 2000 s in 0.5 M H₂SO₄ and 1 M CH₃OH. Figure 12 shows the specific current density versus time (I–t) curves. The current densities of the P₂₀R₀S₀/C3, P₂₀R₀S₃₀/C3, P₂₀R₁₀/C3, and P₂₀R₁₀S₁₅/C3 nanocatalysts at 2000 s are 1 mA/g, 4 mA/g, 5 mA/g, and 9 mA/g, respectively. The long-term stability of ₂₀R₀S₃₀/C3, P₂₀R₁₀/C3, and P₂₀R₁₀S₁₅/C3 is obviously better than that of commercial 30 wt% Pt/XC-72 (Figure 12). Although P₂₀R₀S₀/C3 achieved steady state immediately after the reaction began, the current densities of the three other catalysts declined slightly to various extents before stabilizing. This initial fast decay can be attributed to the adsorption of MOR intermediates such as CO_ads, CH₃OH_ads, and CHO_ads during the electrochemical MOR [40, 41]. The current decayed gradually for an extended period of time before the pseudo-steady-state was achieved; this decay can be attributed to adsorbed SO42− anions on the catalyst’s surface, which can restrict the MOR [40]. The lower stability can also be partly caused by larger and/or agglomerated metal NPs on the carbon support. Under anodic oxidation conditions in the acidic medium, degradation of catalytic performance generally stems from the tendency of noble metal NP aggregation due to Ostwald ripening [42, 43].

Among all these catalysts, only P₂₀R₀S₀/C3 shows poor durability. Due to CO poisoning, P₂₀R₀S₀/C3 demonstrates a steep decline in its current density to 1 mA⋅g⁻¹. The addition of 30 wt% Sn (i.e., P₂₀R₀S₃₀/C3) effectively enhances the catalyst’s durability, where the current at 2000 s reaches 4 mA/g. Notably, this density is almost identical to that achieved by the well-known Pt₂₀Ru₁₀ catalyst composition (i.e., P₂₀R₁₀S₀/C3; 5 mA⋅g⁻¹ at 2000 s). Although P₂₀R₀S₃₀/C3 exhibits 80% performance of the P₂₀R₁₀S₀/C3 catalyst, the price of Sn is only a fraction (1/114) of the cost of the precious metal Ru (Ru: 66 USD/ounce; Sn: 0.58 USD/ounce). Given the current price of Pt (980 USD/ounce), our proposed composition could reduce the anode catalyst costs by up to 6%. Clearly, the results suggest that it is economically prudent to replace Ru by Sn in DMFC anode catalysts.

Furthermore, the P₂₀R₁₀S₁₅/C3 catalyst shows the most moderate decline among these catalysts (Figure 8). This result indicates that the P₂₀R₁₀S₁₅/C3 catalysts have the highest durability for the MOR relative to the other catalysts, which may be due to the synergistic effect involving the Pt, Ru, and Sn atoms. Due to the activation of interfacial water preferentially adsorbed at the SnO₂ sites, the P₂₀R₁₀S₁₅/C3 catalyst demonstrates superior resistance to CO poisoning and exhibits a higher current density [12]. In addition, an abundance of metal oxides (i.e., SnO₂ in this study) can protect Pt NPs from aggregation. Thus, the P₂₀R₁₀S₁₅/C3 catalysts with an optimal Sn content demonstrated the best stability during the MOR.

Finally, the cyclic durability of our proposed electrocatalyst and commercial 30 wt% Pt/XC-72 was also examined, as shown in Supplementary Figure S2, which indicates that the MOR activity improved by 15% after 500 cycles. However, the MOR activity of the commercial 30 wt% Pt/XC-72l reduced to 40% of its original value. It can be suggested that our proposed catalyst composition provides a potential route to improve the cyclic durability of DMFC.