Synthesis and characterization of Pt nanoparticles on sulfur-modified carbon nanotubes for methanol oxidation

Pt nanoparticles supported on carbon nanotubes (Pt/CNTs) have been synthesized from sulfur-modified CNTs impregnated with H₂PtCl₆ as Pt precursor. The dispersion and size of Pt nanoparticles in the synthesized Pt/CNT nanocomposites are remarkably affected by the amount of sulfur modifier (S/CNT ratio). The results of X-ray diffraction and transmission electron microscopy indicate that an S/CNT ratio of 0.3 affords well dispersed Pt nanoparticles on CNTs with an average particle size of less than 3 nm and a narrow size distribution. Among different catalysts, the Pt/CNT nanocomposite synthesized at S/CNT ratio of 0.3 showed highest electrochemically active surface area (88.4 m² g⁻¹) and highest catalytic activity for methanol oxidation reaction. The mass-normalized methanol oxidation peak current observed for this catalyst (862.8 A g⁻¹) was ∼ 6.5 folds of that for Pt deposited on pristine CNTs (133.2 A g⁻¹) and ∼ 2.3 folds of a commercial Pt/C (381.2 A g⁻¹). The results clearly demonstrate the effectiveness of a relatively simple route for preparation of sulfur-modified CNTs as a precursor for the synthesis of Pt/CNTs, without the need for tedious pretreatment procedures to modify CNTs or complex equipments to achieve high dispersion of Pt nanoparticles on the support.     

Structural designing of Pt-CeO2/CNTs for methanol electro-oxidation

In an attempt to utilize CeO₂ as a co-catalyst with Pt for methanol electro-oxidation, Pt-CeO₂/CNTs were prepared through structural designing by adsorbing Pt nanoparticles on CeO₂ coated CNTs. X-ray Diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) were used to analyze the composition of the prepared catalysts. Zeta potential analysis, high resolution transmission electron microscopy (HRTEM) and cyclic voltammetry (CV) methods indicated that Pt nanoparticles are selectively adsorbed on CNTs other than CeO₂ surface. Pt-CeO₂/CNTs were compared with Pt supported on CNTs in terms of electrochemical active surface (EAS) areas, methanol electro-oxidation activity, and chronoamperometry, results indicating that CeO₂ can enhance the catalytic activity of Pt for methanol electro-oxidation with no apparent decrease of EAS. The CO stripping test showed that CeO₂ can make CO stripped at a lower potential, which is helpful for CO and methanol electro-oxidation.     

Effect of noble metal species and compositions on manganese dioxide-modified carbon nanotubes for enhancement of alcohol oxidation

By integrating the effects of alloying, chemical composition and support, a series of mono- and bi-metallic catalyst nanoparticles electrodeposited on α-manganese dioxide (MnO₂)-modified carbon nanotube (CNT) supports were synthesized to improve the efficiency of direct alcohol fuel cells. Small and dispersed nanoparticles on the CNT/MnO₂ surfaces with high electrochemically active surface area (ECSA) were successfully obtained in this work. The support materials were characterized by Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD), while the as-prepared catalysts were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and chronoamperometry (CA) were used to study the activity and stability of the catalysts, respectively. The results showed that a combination of Pt, Pd, Au and MnO₂ on the CNTs significantly affected the topography of the composite catalyst surfaces, and their electrochemical measurements showed excellent electrocatalytic activity toward the reaction. For methanol and ethanol oxidation in acid solution, CNT/MnO₂/1M3Pt (M = Pd or Au) catalysts revealed greater activity improvement compared to the other prepared catalysts. For the bimetallic CNT/MnO₂/xMyPt catalysts, the values of the forward peak current (I_f)) and the ratio of the forward peak current to the reverse peak current (I_f/I_b) were higher, while their onset potentials (E_o) were lower compared to those of the monometallic CNT/MnO₂/4Pt catalyst. Moreover, CO oxidation on these bimetallic catalysts was also confirmed to be poisoning resistant. These results indicate that our prepared catalyst showed excellent electrocatalytic performance, reliability, and stability. The catalytic activity improvement was based upon the unique integrated structural and functional properties and the synergistic effect of different compositions in the catalyst system.     

Multiwalled carbon nanotube-supported Pt/Sn and Pt/Sn/PMo12 electrocatalysts for methanol electro-oxidation

Carbon nanotube (CNT) containing electrocatalysts, Pt/Sn/PMo₁₂/CNT, Pt/Sn/CNT, and Pt/CNT, were prepared by a microwave-heated polyol process. The electrocatalysts were characterized by X-ray diffraction, energy dispersive spectroscopy, scanning and transmission electron microscopy, and cyclic voltammetry. We found that the addition of PMo₁₂ can help Pt-Sn nanoparticles to disperse very uniformly on the outer walls of CNTs. The Pt/Sn/PMo₁₂/CNT catalyst exhibited the lowest onset potential for electro-oxidation of adsorbed C intermediates, compared to the Pt/Sn/CNT and Pt/CNT catalysts. It also generated much higher current density for methanol oxidation at room temperature compared to Pt/Sn/CNT and Pt/CNT catalysts, which were prepared by the same method.     

Sulfated zirconium oxide as electrode and electrolyte additive for direct methanol fuel cell applications

Sulfated zirconium oxide (S-ZrO₂) was used as electrode and electrolyte additive for direct methanol fuel cells (DMFCs). Composite Nafion electrolyte membranes and Pt electrocatalysts, both containing S-ZrO₂ at different content, were prepared. The morphology and catalytic activity of prepared catalysts were investigated by scanning electron microscopy, and voltammetric technique. Results indicated that Pt/S-ZrO₂ catalysts showed enhanced efficiency towards oxygen reduction reaction and increased methanol tolerance as compared to bare platinum. Pt/S-ZrO₂-based carbon cloth electrodes were prepared and assembled as cathode in a DMFC, with Nafion/S-ZrO₂ as composite electrolyte membrane. With respect to bare platinum and Nafion, higher values of current and power density were recorded at 110 °C. The use of S-ZrO₂ both as catalyst and electrolyte additive provided enhanced membrane/electrode interface stability, as revealed by EIS spectra recorded during cell operation.     

Effect of preparation conditions on the performance of nano Pt‒CuO/C electrocatalysts for methanol electro-oxidation

Nano PtCuO particles were deposited on Vulcan XC-72R carbon black using the impregnation and microwave irradiation methods. The prepared catalysts were characterized by XRD, TEM and EDX analyses. TEM images indicated that the microwave method provides homogeneously distributed catalyst particles in smaller size, compared to the one prepared by the impregnation method. The electrocatalytic activity of Pt?CuO/C electrocatalysts was investigated to oxidize methanol in 0.5 M H₂SO₄ solution by applying cyclic voltammetry and chronoamperometry techniques. The oxidation current density of Pt?CuO/C electrocatalyst, prepared by the microwave method, showed two folds increment with a potential shift in the negative direction by 69 and 36 mV at the first and second oxidation peaks, respectively, relative to those at the catalyst prepared by the impregnation method. The effect of varying methanol concentration on the resulting oxidation current density of Pt?CuO/C electrocatalysts was studied. Some kinetic information about the reaction order with respect to methanol and Tafel slope values was calculated. Slower current density decay was observed in the chronoamperogram of Pt?CuO/C electrocatalyst, prepared by the microwave method, reflecting a lower degree of surface poisoning.     

Rapeseed meal-based autochthonous N and S-doped non-metallic porous carbon electrode material for oxygen reduction reaction catalysis

The heteroatom-doped porous carbon material as an alternative to commercial Pt/C catalysts in oxygen reduction reaction has attracted extensive attention. In this study, the rapeseed meal-based material (ARM-900) prepared by carbonization with high temperature and activation with ZnCl₂ had a porous structure and was doped with N and S heteroatoms. Compared to commercial Pt/C catalysts (onset potential of 0.95 V vs. RHE and limiting diffusion current of ?5.7 mA cm^?2), ARM-900 demonstrated excellent electrocatalytic performance with an onset potential of 0.98 V vs. RHE and limiting diffusion current of ?8.1 mA cm^?2 in O₂ saturated 0.1 M KOH solution. Meanwhile, ARM-900 had higher durability and more superior methanol tolerance than Pt/C catalyst. The excellent ORR performance of ARM-900 was derived from the formation of abundant pore structure and the doping of the autochthonous N and S heteroatoms. MFCs with ARM-900 as the cathode had the maximum power density of 808 mW/m², which was obviously better than Pt/C (709 mW/m²). This study provided an environment-friendly and effective strategy for the reuse of rapeseed meal and the preparation of N and S-doped non-metallic ORR catalysts.     

Titanium carbide nanoparticles supported Pt catalysts for methanol electrooxidation in acidic media

Titanium carbide (TiC) nanoparticles supported Pt catalyst for methanol electrooxidation is investigated for the first time. The resultant TiC/Pt catalysts are prepared by using a simple electrodeposition to load Pt nanoparticles on TiC nanocomposite. The electrodes are characterized by scanning electron microscopy and cyclic voltammetry. It is found that the TiC/Pt catalysts help alleviate the CO poisoning effect for methanol electrooxidation with a higher ratio of the forward anodic peak current (I_f) to the reverse anodic peak current (I_b). The improvement in the catalytic performance is attributed to the fact that TiC ameliorates the tolerance to CO adsorption on Pt nanoparticles. One possible mechanism to improve the CO tolerance of Pt taking TiC as supporting material in methanol electrooxidation is also proposed. The results suggest that TiC could be practical supporting materials to prepare electrocatalysts that are suitable for the methanol electrooxidation applications.     

Functionalization of electrochemically prepared titania nanotubes with Pt for application as catalyst for fuel cells

Titania nanotubes (TiNTs) were prepared by electrochemical anodization and were used as a support for depositing Pt. After annealing the TiNTs changed to crystalline anatase phase and were doped with carbon. The TiNTs/Pt/C was tested as electrode for electrochemical catalysis of methanol oxidation. The composite catalyst activities were measured by cyclic voltammetry in 1 M CH₃OH + 1 M H₂SO₄. The results demonstrated that TiNTs/Pt/C can greatly enhance the catalytic activity of methanol oxidation. The CO stripping led to the increase in the current peak of methanol oxidation due to activating the catalyst surface by point defect formation. Moreover, the higher ratio of the forward anodic peak current to the reverse anodic peak current indicates more effective removal of the poisonous species.     

Fabrication of a bimetallic Cu/Pt particle-modified carbon nanotube paste electrode and its use for the electrocatalytic oxidation of methanol

In this work, carbon nanotube paste electrode (CNTPE) was used as a substrate for deposition of bimetallic Cu/Pt particles. At first, a Cu film was prepared by electrochemical reduction of Cu ions onto the CNTPE in 0.1 M H₂SO₄ solution. Cu/Pt catalysts were prepared by partial galvanic replacement of Cu with Pt by simply immersion of the Cu-coated CNTPE in 2.0 mM H₂PtCl₆ solution. The nature and surface morphology of the bare CNTPE and fabricated Cu/Pt species were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The Cu/Pt-modified CNTPE exhibits remarkable electrocatalytic activity towards methanol oxidation. It has been shown that carbon nanotubes improve the electrocatalytic activity of the catalysts towards oxidation. Then, the influence of various parameters such as Cu source concentration, electrodeposition time, replacement time, and methanol concentration on its oxidation as well as long-term stability of the modified electrode have been investigated by electrochemical methods.     

Methanol oxidation efficiencies on carbon-nanotube-supported platinum and platinum-ruthenium nanoparticles prepared by pulsed electrodeposition

Dense carbon nanotubes (CNTs, 30-50 nm in diameter, 6-8 μm in length) were grown via a thermal chemical vapor deposition process on titanium treated carbon cloths. Catalysts in the form of either nano-scale platinum (Pt) or platinum-ruthenium (Pt-Ru) particles were then deposited on the CNT surfaces by pulse-mode potentiostatic electrodeposition. Surface morphologies of the prepared electrodes were examined by scanning electron microscopy and transmission electron microscopy. Well dispersed catalysts, Pt alone (particle sizes of 7-8 nm) or Pt-Ru (particle sizes of 3-4 nm) nanoparticles, were successfully electrodeposited on the CNT surfaces in citric acid aqueous solutions. In addition, electrochemical characteristics of the specimens were investigated by cyclic voltammetry in argon saturated sulfuric acid aqueous solutions and in mixed sulfuric acid and methanol aqueous solutions. The catalytic activity of the Pt-Ru/CNTs electrode for methanol oxidation was 1038.25 A g⁻¹_Pt in a mixed solution containing 0.5 M sulfuric acid and 1.0 M methanol.     

Carbon nanotube-supported Pt-Alloyed metal anode catalysts for methanol and ethanol oxidation

To improve the electrocatalytic activity of alcohol oxidation, functionalized carbon nanotubes (CNTs) decorated with various compositions of metal alloy catalyst nanoparticles (Pt_xM_y, where M = Au and Pd; x and y = 1–3) have been prepared via reduction. The CNTs were treated with an nitric acid solution to promote the oxygen-containing functional groups and further load the metal nanoparticles. X-ray diffraction (XRD) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to probe the formation of catalyst microstructure morphologies. A uniform dispersion of the spherical metal particles with diameters of 2–6 nm was acquired. The catalytic properties of the catalyst for oxidation were thoroughly studied by electrochemical methods that involved in the cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). To maximize the electrocatalytic performance and minimize the metal integration of the loaded CNTs, various compositions of active catalysts with large active surface areas are expected to increase the activity of the enhanced catalysts for alcohol oxidation. Most of the prepared bimetallic catalysts have better alcohol oxidation kinetics than commercial PtRu/C. Among the prepared catalysts, the PtAu/CNTs and PtPd/CNTs catalysts with high electrochemically active surface area (ECSA) show excellent activities for alcohol oxidation resulting in their low onset potentials, small charge transfer resistances and high peak current densities and I_f/I_b ratios, stability, and better tolerance to CO for alcohol oxidation. The integration of Pt and different metal species with different stoichiometric ratios in the CNTs support affects the electrochemical active surface area achieved in the catalytic oxidation reactions.     

Effects of catalyst preparation route and promoters (Ce and Zr) on catalytic activity of CuZn/CNTs catalysts for hydrogen production from methanol steam reforming

Ce or Zr promoted CuZn/CNTs (carbon nanotubes) catalysts were synthesized by microwave-assisted polyol, co-precipitation and impregnation methods and were used to generate hydrogen by methanol steam reforming (MSR) process. The physico-chemical properties of the prepared catalysts were analyzed by BET, XRD, FT-IR, TEM, FE-SEM, EDX-dot mapping and H₂-TPR methods. The effect of various operating parameters on methanol conversion and selectivity of gaseous products was investigated. The results indicated that the addition of 2 wt% CeO₂ promoter on CuZn/CNTs catalyst synthesized by impregnation route (CuZn/CNTs (Imp)) increased its methanol conversion from 81.3 to 85.2%, and decreased its CO selectivity from 6.2 to 3.8% at 300 °C, WHSV of 7.5 h^?1 and S/C molar ratio of 2. In addition, the CeCuZn/CNTs catalyst prepared via the microwave-assisted polyol route (CeCuZn/CNTs (Pol)) exhibited the best catalytic activity with 98.2% hydrogen selectivity, 2.6% CO selectivity and 94.2% methanol conversion at 300 °C. Furthermore, a 48 h continuous MSR reaction at 300 °C, identified CeCuZn/CNTs (Pol) as the most stable catalyst due to its higher metal particle dispersion and better interaction between the active phase and the CNTs support.     

Displacement triangular Ag/Pd nanoplate as methanol- tolerant electrocatalyst in oxygen reduction reaction

Porous triangular Ag/Pd nanoplates with different alloy ratios, including Ag₁₈Pd₁, Ag₁₈Pd_1.5, and Ag₁₈Pd₂, were successfully prepared by a galvanic displacement reaction. These alloy nanoplates were then used as methanol-tolerant electrocatalysts in an alkaline oxygen reduction reaction (ORR). Electrochemical measurements were conducted using an ultrathin film rotating ring-disk electrode. The mass activity was found to decrease in the order Ag₁₈Pd₁ > Ag₁₈Pd₂ > Ag₁₈Pd_1.5 > Pt nanoparticles > Pd nanoparticles, similar to an observation made in a past analysis of the nanoplates in an electrolyte of free methanol; this indicates that these nanoplate catalysts are more economical than Pd nanoparticles, and even Pt nanoparticles. Additionally, compared to the reactive direction in the case of Pt and Pd nanoparticles toward methanol oxidation in an ORR electrolyte with methanol, all Ag/Pd nanoplate catalysts experienced cathodic currents, which indicate that ORRs occurred even in the presence of methanol. Despite working in a methanol-tolerant solution, the prepared alloy nanoplates still exhibited high electroactivity.     

Precise control of π-conjugated polymer/carbon nanotubes heterointerfaces for oxygen reduction reactions

Nitrogen-coordinated metal catalyst has been regarded as a promising candidate for precious platinum for oxygen reduction reaction (ORR). However, controlling the structure and composition of coordinated metals in heterogeneous catalysts remains a synthetic bottleneck. Here, we design and fabricate π-conjugated polymer/CNTs heterointerfaces by polymerizing Co-BTA on CNTs. Co-BTA contains abundant Co–N₄ moieties and provides catalytic sites for ORR. CNT acts as a support and constructs the network for electron transport. Therefore, Co-BTA/CNT exhibits outstanding catalytic activity for ORR with comparable half-wave potential to commercial Pt/C. Furthermore, Co-BTA/CNT demonstrates better durability and methanol tolerance compared with Pt/C. Importantly, zinc-air batteries with Co-BTA/CNT have a maximum discharge power of 94.5 mW cm⁻² and a high energy density of 985 Wh kg⁻¹, superior to that with commercial Pt/C (51.5  mW cm⁻², 930 Wh kg⁻¹). This work paves a new avenue for precisely controlling nitrogen-coordinated metal catalysts for electrochemical energy conversion and storage.     

Microwave-assisted polyol synthesis of Pt-Zn electrocatalysts on carbon nanotube electrodes for methanol oxidation

Bimetallic Pt-Zn catalysts with high and stable electrochemical activity towards sulfuric acid and methanol oxidation were synthesized by microwave-assisted polyol (MP) method. A catalytic chemical vapor deposition was used to directly grow multi-layered carbon nanotubes (CNTs) on carbon paper substrate. The as-grown CNT forest serves as a support for the Pt-Zn catalysts having a mean size of 3-5 nm. The catalytic activities of the supported Pt-Zn catalysts toward acid electrolyte and methanol oxidation were examined by cyclic voltammetry test with potential cycling. Experimental results confirmed that two-stage MP synthesis enables the improvement of electrochemical activity, antipoisoning ability and long-term durability of the binary catalyst. This improvement can be attributed to the bifunctional mechanism of the binary catalysts: the Zn content serves as a promoting center for the generation of Zn-OH species, and more Pt sites are thus available for methanol oxidation. Accordingly, the Pt-Zn/CNT catalyst, prepared by the MP approach, displays a potential candidate for fuel cell application due to its easy fabrication (6 min), low cost and no additional reduction process.     

An efficient Co-N/C electrocatalyst for oxygen reduction facilely prepared by tuning cobalt species content

Transition metal and nitrogen co-doped carbon catalysts for the oxygen reduction reaction (ORR) have emerged as promising candidates to replace the expensive platinum catalysts but still remain a great challenge. Herein, a novel and efficient nitrogen-doped carbon material with metal cobalt co-dopant (Co–N/C) has been prepared by pyrolyzing porphyrin-based covalent organic polymer where Co is anchored. The optimized 10%-Co-N/C catalyst through facilely and efficiently tuning the cobalt content is carefully characterized by XRD, Raman, XPS, SEM and TEM for composition and microstructure analysis. This catalyst with only 0.56% Co exhibits an excellent ORR catalytic activity with a positive half-wave potential of 0.816 V (vs. RHE) in 0.1 M KOH solution, which is comparable to that of commercial Pt/C (20 wt%). Notably, the 10%-Co-N/C catalyst displays better electrochemical stability with only a loss of 5.1% of its initial current density in chronoamperometric measurement and also gives rise to stronger methanol tolerance than Pt/C. The good ORR catalytic behaviour for this catalyst may be attributed to the dispersion of the Co-N_X active sites via adjusting the contents of cobalt species in porous organic framework.     

Hydrogen production over highly active Pt based catalyst coatings by steam reforming of methanol: Effect of support and co-support

The effect of metal oxide (CeO₂, Al₂O₃ and ZrO₂) support and In₂O₃ co-supported Pt catalysts has been investigated on steam reforming of methanol in microreactors. CeO₂, Al₂O₃ and ZrO₂ were prepared by the sol-gel method and they were used as a support, which was impregnated with In₂O₃ as co-support followed by the introduction of Pt species via the wet impregnation method. The size and dispersion of the Pt nanoparticles on In₂O₃/support have been examined by transmission electron microscopy. From these TEM and XPS results, it was found that the addition of In₂O₃ supports the formation of a high concentration of metallic Pt nanoparticles with enhanced dispersion and controlled particle size on the surface. The activity and stability of all the developed catalysts were tested for the steam reforming of methanol in microreactors at different temperatures. Under reforming conditions without prior reduction, a Pt/CeO₂ catalyst containing 15 wt % of Pt exhibited complete methanol conversion and high selectivity towards hydrogen at 350 °C. However, the CO formation was found to be very high (7.0 vol %) for this catalyst. Upon addition of In₂O₃ as a co-support to this formulation the formation of CO decreased considerably. Pt/In₂O₃/CeO₂ catalyst containing 15 wt % of Pt and 15 wt % of In₂O₃ showed excellent catalytic performance at much lower concentration of CO. This change could be closely associated with the formation of metallic Pt nanoparticles with smaller size, higher dispersion with strong interaction between Pt, In₂O₃ and support, which creates more oxygen vacancies to activate the water molecule which then react with methanol to produce H₂ and CO₂ suppressing the CO formation. Moreover, CeO₂ supported Pt/In₂O₃ catalyst displayed higher stability with lowest CO formation under continuous steam reforming operation of 100 h. The superior performance of this catalyst is thought to be due to the relative abundance of redox sites on the CeO₂ surface, which is able to create an oxygen vacancy as it possesses higher oxygen storage capacity and oxygen exchange capacity. This work demonstrates that the nature of support plays a crucial role for the continuous activation of reactants and determines the catalytic stability during methanol steam reforming.     

Electrochemical synthesis and characterization of carbon-supported Pt and Pt–Ru nanoparticles with Cu cores for CO and methanol oxidation in polymer electrolyte fuel cells

Pt and Pt–Ru shells on Cu cores supported on Vulcan carbon XC72R have been synthesized and tested as possible anode electrocatalysts for polymer electrolyte fuel cells. Pt(Cu)/C was prepared by Cu electrodeposition on the black carbon support at constant potential followed by Pt deposition on Cu by galvanic exchange, whereas Pt–Ru(Cu)/C was prepared by spontaneous deposition of Ru species on Pt(Cu)/C. The corresponding cyclic voltammograms in 0.5 M H₂SO₄ solution showed the hydrogen adsorption/desorption peaks and no Cu oxidation. The respective CO stripping peak potentials of Pt(Cu)/C and Pt–Ru(Cu)/C were about 0.1 and 0.2 V more negative than those corresponding to Pt/C and Ru-decorated Pt/C. The best conditions for CO oxidation were found for Cu deposition potentials between −0.2 and −0.4 V vs. Ag/AgCl/KCl(sat). The Pt economy of the Pt–Ru(Cu)/C system was proved for the methanol oxidation, with specific currents more than twice those obtained on the Ru-decorated commercial Pt/C catalysts.     

Design and preparation of highly active carbon nanotube-supported sulfated TiO2 and platinum catalysts for methanol electrooxidation

A novel electrocatalyst structure of carbon nanotube-supported sulfated TiO₂ and Pt (Pt-S-TiO₂/CNT) is reported. The Pt-S-TiO₂/CNT catalysts are prepared by a combination of improved sol-gel and ethylene glycol reduction methods. Transmission electron microscopy and X-ray diffraction show that the sulfated TiO₂ is amorphous and is coated uniformly on the surface of the CNTs. Pt nanoparticles of about 3.6 nm in size are homogenously dispersed on the sulfated TiO₂ surface. Fourier transform infrared spectroscopy analysis proves that the CNT surfaces are modified with sulfated TiO₂ and a high concentration of SO_x, and adsorbed OH species exist on the surface of the sulfated TiO₂. Electrochemical studies are carried out using chronoamperometry, cyclic voltammetry, CO stripping voltammetry and impedance spectroscopy. The results indicate that Pt-S-TiO₂/CNT catalysts have much higher catalytic activity and CO tolerance for methanol electrooxidation than Pt/TiO₂/CNTs, Pt/CNTs and commercial Pt/C.