Initial Electrochemical Surface Area Research Articles

A structured catalyst support combining electrochemically exfoliated graphene oxide and carbon black for enhanced performance and durability in low-temperature hydrogen fuel cells

Reduced electrochemically exfoliated graphene oxide (rEGO) is combined with carbon black (CB) as a hybrid support material to improve platinum (Pt) catalyst electrochemical activity and durability. Pt/rEGO2-CB3 (rEGO/CB ratio 2/3) retains 71% of initial electrochemical surface area (ECSA) and maintains higher oxygen reduction reaction (ORR) activity compared to Pt/CB after 30000 cycles of the accelerated stress test (AST). In addition, Pt/rEGO2-CB3 shows a 1.8 times improvement in the hydrogen fuel cell performance compared with Pt/CB and is more stable after 24 h at a continuous 0.60 V. The Pt/rEGO2-CB3 promotes the 4e− reaction pathway demonstrated by linear sweep voltammetry (LSV), which leads to greater ORR activity. In addition, the combination of rEGO and CB leads to both enhanced transport properties and improved stability. The Pt particles on both CB and rEGO are less likely to agglomerate in the composite support than in either of the two carbon supports when used alone.

Preferential Protection of Low Coordinated Sites in Pt Nanoparticles for Enhancing Durability of Pt/C Catalyst

Protecting low coordinated sites (LCS) of Pt nanoparticles, which are vulnerable to dissolution, may be an ideal solution for enhancing the durability of polymer electrolyte fuel cells (PEMFCs). However, the selective protection of LCSs without deactivating the other sites presents a key challenge. Herein, we report the preferential protection of LCSs with a thiol derivative having a silane functional group, (3-mercaptopropyl) triethoxysilane (MPTES). MPTES preferentially adsorbs on the LCSs and is converted to a silica framework, providing robust masking of the LCSs. With the preferential protection, the initial oxygen reduction reaction (ORR) activity is marginally reduced by 8% in spite of the initial electrochemical surface area (ECSA) loss of 30%. The protected Pt/C catalyst shows an ECSA loss of 5.6% and an ORR half-wave potential loss of 5 mV after 30,000 voltage cycles between 0.6 and 1.0 V, corresponding to a 6.7- and 2.6-fold durability improvement compared to unprotected Pt/C, respectively. The preferential protection of the vulnerable LCSs provides a practical solution for PEMFC stability due to its simplicity and high efficacy.

Pt supported on boron, nitrogen co-doped carbon nanotubes (BNC NTs) for effective methanol electrooxidation

The research for electrocatalyst with high electroactivity and great CO-resistance ability for direct methanol fuel cells (DMFCs) is still a huge challenge. In this report, we develop Boron, Nitrogen co-doped carbon nanotubes (BNC NTs) as a support for Pt. Owing to the doping of boron, the catalyst not only provides extremely active sites for methanol oxidation reactions (MOR) but also protects Pt nanoparticles from agglutinating, performing superior electroactivity and excellent ability to anti CO poisoning. The X-ray photoelectron spectroscopy (XPS) results demonstrate the strong electron effect between Pt and B. Notably, the Pt/BNC NTs catalyst exhibits higher catalytic activity towards MOR and more superior durability in comparison with Pt/NC NTs and commercial JM Pt/C catalyst. The accelerated durability test (ADT) illustrates that Pt/BNC NTs catalyst can improve the issue of electrochemical surface area (ECSA) conservation, with only 30% diminish in comparison with the initial ECSA after 5000 cycles. The experiment result demonstrate that boron doping is the key step to improve the catalytic activities and CO-resistance ability due to the combination effects, involving firm B–C and N–C bonds, the stronger electron transfer in the nanotube structure among Pt, B and N, the stronger adsorption intensity of oxygen species from doped B.

Improved bi-functional oxygen electrocatalytic performance of Pt–Ir alloy nanoparticles embedded on MWCNT with Pt-enriched surfaces

Multi-walled carbon nanotube supported Pt–Ir nanoparticles (Pt–Ir/MWCNT) with different elemental ratios were synthesized by one-pot co-reduction approach under ambient conditions. The Pt–Ir catalysts exhibit improved bi-functional activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and its electrocatalytic performance was clearly established using different physiochemical characterization techniques. The Pt–Ir composition of 2:1 has a higher electrochemical surface area (ECSA) of about 85.3 m2/g compared to other compositions (3:1 and 1:1) and Pt/MWCNT due to the effect of particle size distribution. The improved ORR/OER activity was found to be 139.4 and 740 mA/mg, respectively, for Pt–Ir(2:1)/MWCNT with the potential difference of 760 mV for oxygen bi-functional activity. Furthermore, Pt–Ir(2:1)/MWCNT showed much better stability for ORR compared to other compositions and Pt/MWNCT catalysts, i.e., around 76% of its initial ECSA retained with <20 mV shift in half-wave potential was obtained even after 10,000 potential cycles in acidic medium. It is believed that the Pt enriched surface, amount of Ir content, induced electronic and geometric effects play a vital role on the electrocatalytic activity enhancement of Pt–Ir(2:1)/MWNCT as effective bi-functional oxygen electrode.

Improved activity and stability of Ag–Rh network-like nanoalloy as support-free electrocatalyst for oxygen reduction in alkaline fuel cells

In this study, a simple and environmentally amicable synthesis procedure for support-free silver–rhodium (Ag–Rh) bimetallic network-like nanoalloy was used to catalyze an oxygen reduction reaction in an alkaline medium. The support-free network-like morphology of Ag–Rh nanoalloy exhibits a higher electrochemical surface area (ECSA) of 65.6 m2/g than carbon (VC) supported Ag–Rh (23.8 m2/g). In comparison to the reported benchmark Ag-based electrocatalysts, it presents an improved mass and specific activity of 971.1 mA/mg and 1.45 mA/cm2, respectively. Based on the durability test, the support-free Ag–Rh catalyst retains ∼70% of its initial ECSA after 7000 potential cycles, and Ag–Rh/VC possesses only 20% after 5000 potential cycles due to the surface oxidation of carbon support. Hence, the superior electrocatalytic performance attributed to the support-free morphology and alloy formation with Rh was clearly demonstrated, which could potentially be the choice of the cathodic electrocatalyst for alkaline fuel cells.

Boosting Pt oxygen reduction reaction activity and durability by carbon semi-coated titania nanorods for proton exchange membrane fuel cells

We report a simple, scalable approach to improve interfacial characteristics of carbon semi-coated titania nanorods-supported-Pt with superior peak power density as compared to Pt/C with thin metal loading of 150 μg cm−2. Thin layer of carbon coated titania nanorod is synthesized by hydrothermal method. Carbon coated titania nanorods boosts the Pt oxygen reduction reaction activity than carbon. The crystal structure, dispersion of platinum nanoparticles, surface morphology and oxidation state are studied by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. Studies using conventional three electrode setup shows that Pt/CCT-30 retains 48% of initial electrochemical surface area even after 40,000 potential cycles between 0.6 and 1.2 V. The solid fuel cell mode accelerated stress durability studies show that thin layer of carbon coated titania nanorods-Pt (Pt/CCT 30) significantly enhances stability and preserves 75% of initial fuel cell performance even after 10,000 potential cycles between 1 and 1.5 V. In comparison, only 20% of performance is retained for Pt supported on carbon after 3000 cycles.

PtRu nanoparticles embedded in nitrogen doped carbon with highly stable CO tolerance and durability

As is well known, the lower durability and sluggish methanol oxidation reaction (MOR) of PtRu alloy electrocatalyst blocks the commercialization of direct methanol fuel cells (DMFCs). Here, we design a new PtRu electrocatalyst, with highly stable CO tolerance and durability, in which the PtRu nanoparticles are embedded in nitrogen doped carbon layers derived from carbonization of poly(vinyl pyrrolidone). The newly fabricated electrocatalyst exhibits no loss in electrochemical surface area (ECSA) and MOR activity after potential cycling from 0.6–1.0 V versus reversible hydrogen electrode, while commercial CB/PtRu retains only 50% of its initial ECSA. Meanwhile, due to the same protective layers, the Ru dissolution is decelerated, resulting in stable CO tolerance. Methanol oxidation reaction (MOR) testing indicates that the activity of newly fabricated electrocatalyst is two times higher than that of commercial CB/PtRu, and the fuel cell performance of the embedded PtRu electrocatalyst was comparable to that of commercial CB/PtRu. The embedded PtRu electrocatalyst is applicable in real DMFC operation. This study offers important and useful information for the design and fabrication of durable and CO tolerant electrocatalysts.

High Durability and Performance of a Platinum Electrocatalyst Supported on Sulfonated Macromolecules Coated Carbon Nanotubes

AbstractLow durability and fuel cell performance block the widespread application of polymer electrolyte fuel cells (PEFCs). Here, we deposit platinum nanoparticles on carbon nanotubes (CNTs) before coating by end‐capped hyperbranched sulfonated macromolecules (E‐HBM), which could provide sufficient proton conductivity in catalyst layer thanks to the presence of −SO3H groups. The fabricated electrocatalyst loses 43 % of initial electrochemical surface area (ECSA) after 200 000 potential cycles from 1.0 V to 1.5 V vs. RHE, which is 3 and 20 times higher than that of noncoated and commercial electrocatalysts, respectively. The mass and specific activities of newly fabricated electrocatalyst measured before and after durability test are 1.4 times higher than that of commercial carbon black/Pt. Nafion ionomer‐free membrane electrode assembly is fabricated from the newly designed electrocatalyst, and its fuel‐cell performance reaches 668 mW cm−2 with Pt loading of 0.1 mg cm−2, which is twice higher than that of commercial CB/Pt thanks to the homogeneous conductive macromolecules (E‐HBM) layers on CNTs acting as ionomer and facilitating the proton delivery in the catalyst layer.

Stabilization of PtRu electrocatalyst by nitrogen doped carbon layer derived from carbonization of poly(vinyl pyrrolidone)

Improvements on durability and CO tolerance of the electrocatalyst are crucial for widespread commercialization of direct methanol fuel cells (DMFCs). In this work, we describe a new method to stabilize the PtRu electrocatalyst, in which the PtRu nanoparticles are coated by nitrogen doped carbon layer derived from the carbonization of poly(vinyl pyrrolidone). The coated electrocatalyst shows stable electrochemical surface area (ECSA) and methanol oxidation reaction (MOR) activity after 4200 potential cycles from 0.6 V to 1.0 V vs. RHE; while the non-coated and commercial electrocatalyst lose almost 50% of initial ECSA and MOR activity. Meanwhile, the coated electrocatalyst shows twice higher CO tolerance before and after durability test due to the deceleration of the Ru dissolution proved by the XPS measurement after durability test. The mechanism of the stabilization of Ru was the electron delocalization of Ru caused by the carbonization process of PVP, which changes the electronic structure of Ru and makes Ru difficult to be dissolved. The maximum power density of the coated electrocatalyst is 1.7 times higher than that of commercial CB/PtRu, suggesting the coated electrocatalyst is suitable for real DMFC application. The demonstrated method could be easily extended to obtain extraordinary durability of other electrocatalysts.

Ultrathin nitrogen doped carbon layer stabilized Pt electrocatalyst supported on N-doped carbon nanotubes

The enhancements in fuel cell performance and durability are crucial for the commercialization of polymer electrolyte fuel cells (PEFCs). Here, we deposit platinum nanoparticles on nitrogen doped carbon nanotubes (N-CNT) and continuously coat the electrocatalyst with nitrogen doped carbon (NC) layer derived from the carbonization of poly(vinyl pyrrolidone) (PVP). The NC-coated electrocatalyst shows stable electrochemical surface area (ECSA) during the potential cycling from 0.6 V to 1.0 V vs. RHE; while, the commercial and non-coated electrocatalysts lose 50% and 33% of initial ECSAs, respectively. Moreover, the NC-coated electrocatalyst shows higher oxygen reaction reduction (ORR) activity compared to non-coated electrocatalyst due to the additional nitrogen atoms in the electrocatalyst. The maximum power density of the coated electrocatalyst reaches 676 mW cm−2 with Pt loading of 0.1 mg cm−2, indicating that the mass power density of the electrocatalyst is one of the highest values in recently published literature. The NC layer is significantly important for simultaneous enhancements in durability and fuel cell performance.

Electrocatalyst composed of platinum nanoparticles deposited on doubly polymer-coated carbon nanotubes shows a high CO-tolerance in methanol oxidation reaction

High CO-tolerance and durability of anodic fuel cell electrocatalysts is one of the important factors for commercialization of direct methanol fuel cells (DMFCs). In this study, we describe the preparation of an electrocatalyst composed of poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole] (PyPBI) and poly(vinylphosphonic acid) (PVPA) coated multi-walled carbon nanotubes (MWNTs) on which ∼3 nm Pt nanoparticles (PtNPs) are deposited. The fabricated electrocatalyst shows 1.5-times higher CO tolerance compared to the commercial CB/Pt, which would be due to the wrapping of the CNTs with PVPA by the aid of PyPBI. Meanwhile, the electrocatalyst almost maintains its initial electrochemical surface area (ECSA) and mass activity of the methanol oxidation reaction (MOR) after 10,000 potential cycling in the range of 1–1.5 V vs. RHE. In contrast, the commercial CB/Pt shows almost a 50% loss in its ECSA and mass activity. These results indicate that the durability of the newly fabricated electrocatalyst is quite high and the obtained high CO-tolerance and durability are important for the design of an electrocatalyst for DMFC applications.

Production of high-performance and improved-durability Pt-catalyst /support for proton-exchange-membrane fuel cells with pulsed laser deposition

Pulsed laser deposition in Ar atmosphere is used to deposit Pt nanoparticles onto gas diffusion layer, and its application to proton-exchange-membrane fuel cell is optimized and characterized. When used at anode side, with a Pt loading of 17 μg cm−2 the fuel-cell current density at 0.6 V reaches 1.08 A cm−2, which is close to that of a cell with the anode made by conventional slurry process using E-TEK Pt /C of 200 μg cm−2 Pt loading. The usage of Pt is decreased by 12 fold. Such a low usage of Pt prepared by pulsed laser deposition can be ascribed to the prevention of forming isolated regions that occurs with Pt /C slurry, good dispersion of Pt particles on support, and small particle sizes of 2–3 nm. Furthermore, using accelerated degradation test, it is found that the pulsed laser deposition sample retains 60% of its initial electrochemical surface area after 5000 potential cycles, much higher than that with E-TEK Pt /C, which retains only 7% of its initial electrochemical surface area. The higher electrochemical durability can be attributed to the higher degree of graphitization in the gas diffusion layer used as compared with the carbon black in E-TEK Pt /C, which leads to stronger binding of the Pt nanoparticles onto the carbon support and stronger corrosion resistance of the carbon support.

Nano-size boron carbide intercalated graphene as high performance catalyst supports and electrodes for PEM fuel cells

The low utilization and stability of noble-metal catalysts is always a big barrier to commercialize proton exchange membrane (PEM) fuel cells. Here we report a positive progress on stabilizing the catalyst by modulating 2D graphene as an advanced support of Pt nanoparticles, where the interlayer of graphene is near perfectly intercalated by nano-B4C ceramics. The strong restriction effect of nano-ceramics in graphene interlayers, can greatly improves the usage and electrochemical stability of Pt catalysts. As results, our new graphene/B4C supported Pt catalyst (Pt-RGO/B4C) shows greatly enhanced electrochemical surface area (121 m2 g−1) and mass activity (185 A g−1 Pt) towards oxygen reduction reaction (ORR), which is remarkably higher than the reduced graphene oxide (RGO) supported Pt (Pt/RGO) catalyst and the commercial Pt/C catalyst. In addition, the Pt-RGO/B4C electrode also possesses higher fuel cell performance than the Pt/RGO electrode. Especially, after the electrochemical acceleration test for 10000 cycles, our new catalyst presents an excellent stability, even retains 45.2% initial electrochemical surface area, while the Pt/RGO and Pt/C are only 29.7 and 23.4%, respectively. These indicate our unique catalyst is promising to allow the PEM fuel cell have high ORR activity and stability.

Pt Monolayer Shell on Nitrided Alloy Core—A Path to Highly Stable Oxygen Reduction Catalyst

The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC). Here we report on a novel route to synthesize highly active and stable oxygen reduction catalysts by depositing Pt monolayer on a nitrided alloy core. The prepared PtMLPdNiN/C catalyst retains 89% of the initial electrochemical surface area after 50,000 cycles between potentials 0.6 and 1.0 V. By correlating electron energy-loss spectroscopy and X-ray absorption spectroscopy analyses with electrochemical measurements, we found that the significant improvement of stability of the PtMLPdNiN/C catalyst is caused by nitrogen doping while reducing the total precious metal loading.

Effect of Particle Size and Operating Conditions on Pt3Co PEMFC Cathode Catalyst Durability

The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes with the smallest Pt3Co particle size was the highest and that of the largest Pt3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt3Co over the 4.9 nm Pt3Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported.

Titanium cobalt nitride supported platinum catalyst with high activity and stability for oxygen reduction reaction

We describe a facile route to the development of novel robust non-carbon titanium cobalt nitride (Ti0.9Co0.1N) used as a support for Pt, and the catalyst exhibits high activity and stability for the oxygen reduction reaction (ORR). XRD and TEM results show that the synthesized Ti0.9Co0.1N is formed as a single-phase solid solution with high purity. The XPS measurements verified the strong metal/support interaction between Pt nanoparticles (NPs) and the Ti0.9Co0.1N support. Most importantly, Ti0.9Co0.1N supported Pt catalyst (Pt/Ti0.9Co0.1N) exhibits a much higher mass activity and durability than that of the commercial JM Pt/C electrocatalyst for ORR. The accelerated durability test (ADT) reveals that the novel Ti0.9Co0.1N support can dramatically enhance the durability of the catalyst and maintain the electrochemical surface area (ECSA) of Pt. Pt/Ti0.9Co0.1N shows great improvement in ECSA preservation, with only 35% of the initial ECSA drop even after 10 000 ADT cycles. The experimental data indicate that the electronic structure of Pt can be modified by Co doping, and there exists a strong interaction between Pt and the Ti0.9Co0.1N support, both of them are playing an important role in improving the activity and durability of the Pt/Ti0.9Co0.1N catalyst.

Nitrogen Post Modification of PtRu/Carbon Catalysts for Improved Methanol Oxidation Reaction Performance in Alkaline Media

This work compares the methanol oxidation performance and stability of a commercial PtRu/Carbon catalyst post modified with nitrogen against an unmodified counterpart in alkaline media. Commercially available Hi-Spec JM10000 (PtRu) was modified with nitrogen via ion implantation in order to modify those areas not shielded by the pre-existing catalyst. The effects of this process on the structure and chemical composition of the catalyst and carbon support were explored using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), while the electrochemical performance and stability of the catalyst were then investigated using rotating disk electrode experiments. Compared to the unmodified catalyst, the N-modified sample had a higher initial electrochemical surface area, likely resulting from the ablation and redeposition of PtRu during the implantation process. Accelerated degradation test (ADT) results showed that nitrogen modification reduced surface area loss, helped to retain ruthenium, and improved methanol oxidation performance by nearly double. The benefits of nitrogen doping to improve state-of-the-art electrocatalysts combined with advantages of alkaline media improve the viability of widespread commercialization of direct methanol fuel cells.

Pd@Pt core–shell tetrapods as highly active and stable electrocatalysts for the oxygen reduction reaction

Enhancing the electrocatalytic activity and stability of cathodic Pt electrocatalysts in proton exchange membrane fuel cells is an attractive research topic because of the importance of the oxygen reduction reaction (ORR) in PEMFCs. In this work, Pd@Pt core–shell tetrapods (CSNTPs) are prepared by a facile seeded growth process. During the synthesis, Pd tetrapods act as seeds to guide the growth of the dendritic Pt shell. Various physical techniques confirm that the as-prepared Pd@Pt CSNTPs have a core–shell structure and surface dendritic morphology. Moreover, the electrocatalytic activity and durability of the Pd@Pt CSNTPs for the ORR in acidic media were systemically studied by various electrochemical techniques such as cyclic voltammetry, ORR polarization measurements, and accelerated durability test (ADT). After an 8000 cycle ADT, Pd@Pt CSNTPs only lose 13% of their initial electrochemical surface area, whereas commercial Pt black loses 78%. Compared to Pt black, Pd@Pt CSNTPs show remarkably enhanced electrocatalytic activity and durability for the ORR owing to their specific structural characteristics and the synergistic effect between the Pt shell and Pd core.

PEMFC cathode catalyst contamination evaluation with a RRDE-methyl methacrylate

This study was undertaken to provide insight into the mechanism of methyl methacrylate (MMA) contamination on the cathodes in proton exchange membrane fuel cells (PEMFCs). The effect of various concentrations of MMA on the oxygen reduction reaction (ORR) was investigated using a rotating ring-disk electrode (RRDE). The adsorption of MMA on the Pt/C electrode leads to a reduction in the electrochemical surface area (ECSA) and a decrease in the mass activity of the ORR. Increasing the MMA concentration causes an increase in its coverage on Pt and a decrease in the ORR mass activity. At high MMA concentration (0.1 M), the O2 transportation is also affected, resulting in a large decrease in the diffusion limiting current. For all of the MMA concentrations measured, a shift in the ORR reaction pathway from a 4-electron to 2-electron mechanism is observed, as indicated by the increase in the H2O2 production on the ring. Using the RRDE measurements and the Levich plots, the total charge transfer number is confirmed to decrease from 4 for the clean electrode to lower values due to the increase in the H2O2 side reactions. The shift in the reaction pathway is hypothesized to be caused by the inhibition of dual adsorption of the O2 molecules, due to steric hindrance induced by MMA adsorption on the Pt/C electrode. Tafel evaluation indicates a continuous increase in the slope with an increase in the MMA concentration, which indicates that the passage of electrons for the ORR at the electrode surface is altered by the adsorption of MMA. A recovery effect was also investigated and a water rinsing process was used to recover the electrode. Only a partial recovery was obtained with a water rinse followed by potential cycling over the same potential range as the initial ECSA measurements. The unrecovered performance is attributed to MMA remnants on the catalyst surface, which can be removed by potential cycling over a wider potential range with a larger anodic potential limit.

Pt/SnO2 Electrocatalysts on Conductive Fillers

For polymer electrolyte fuel cells (PEFCs), the electrocatalysts on which Pt nano-particles are homogeneously dispensed on carbon black (Pt/C) are widely used. However, during the fuel cell start-stop cycles, the potential of the cathode can reach up to ca. 1.5VRHE, resulting in a severe carbon corrosion. Tin oxide (SnO2) has been studied as an alternative support material because of its thermochemical stability. We have demonstrated negligible degradation within 60,000 cycles in a half-cell test [1-3], indicating that Pt/SnO2 electrocatalyst can exhibit considerable durability. However, relatively low electrical conductivity in such semiconducting oxides often leads to poor cell performance. Here, we aim to develop Pt/SnO2 electrocatalyst with both high durability and high activity, using conductive fillers as backbones of electrocatalysts. We selected vapor grown carbon fibers (VGCF) and acetylene black (AB) as possible conductive fillers. SnO2/VGCF and SnO2/AB were synthesized via the ammonia co-precipitation method. Then, the impregnation of Pt particles was made using a Pt(acac)2 method to prepare both Pt/SnO2/VGCF and Pt/SnO2/AB. Nanostructure of electrocatalysts was observed by STEM. To evaluate the electrochemical activity of these electrocatalyst, electrochemical surface area (ECSA) was measured by cyclic voltammetry (CV). The durability of electrocatalysts under the cathode condition was evaluated, where the electrocatalysts were subjected to the potential cycles between 1.0 and 1.5 VRHE at a scan rate of 50 mV s-1 in the measurements. Figure 1 shows the nanostructure of Pt/SnO2/VGCF, revealing the selective impregnation of Pt particles on SnO2 rather than the conductive fillers. Figure 2 shows the ECSA of various electrocatalysts as a function of the number of cycles. ECSA of Pt/SnO2/VGCF was about three times as large as that of Pt/SnO2 before CV cycles. After 60,000 cycles, the former is about five times as large as the latter. With respect to the retention of ECSA before and after the CV cycles, Pt/SnO2/VGCF kept 65.0% of the initial ECSA value and Pt/SnO2/AB kept 58.7%. These results indicate that electron-conductive fillers can be used as the conductive backbones of the PEFC electrocatalysts using semiconducting oxide supports. Acknowledgement Financial support by the Grant-in-Aid for Scientific Research (S) (No. 23226015), JSPS Japan, is gratefully acknowledged.