CO-like Species Research Articles

Controlled synthesis of reduced graphene oxide-supported bimetallic Pt–Au nanoparticles for enhanced electrooxidation of methanol

Controlled construction of bimetallic interfaces on conductive carbon supports is extremely important for achieving better synergistic effect required for electrooxidation of small organic molecules for energy applications. Herein, controlled synthesis of reduced graphene oxide (RGO)-supported bimetallic Pt–Au nanoparticles (Pt–Au/RGO) for electrooxidation of methanol using a facile and practical approach was described. By carefully adapting sequential and simultaneous reduction steps H2PtCl6 and AuCl3were reduced on RGO support using ammonia borane (AB) and ascorbic acid (AA) as reducing agents. Three types of Pt–Au/RGO catalysts were prepared and labeled as PtAu/RGO-AB1, PtAu/RGO-AB, and PtAu/RGO-AA. The reduction process was carried at ambient conditions, without the use of surfactants, and the catalysts obtained were analyzed through various techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS). The PtAu/RGO-AB1 catalyst showed remarkable uniformity on the RGO sheets, with an average particle size of 2–3 nm. The electrochemical behavior of Pt–Au catalysts supported on reduced graphene oxide (RGO) for methanol oxidation was systematically investigated via cyclic voltammetry and chronoamperometry techniques. Among the studied catalysts, PtAu/RGO-AB1 exhibited high electrochemical active surface area (ECSA) of 92.47 m2/g, along with the highest mass and ECSA-normalized activities for the electrooxidation of methanol. PtAu/RGO-AB1 manifested exceptional resistance to accumulated CO-like species, as evidenced by its higher forward peak current density to reverse peak current density ratio (If/Ib) of 2.20. The facile and effective synthesis strategy described here provides a promising method for fabricating well-defined multi-component nanostructured electrocatalysts with potential applications for various fuel cell reactions.

Effect of Supporting Pd Nanoparticles on WOx Nanorods on Their Stability and Catalytic Activity Towards the Electrochemical Oxidation of Concentrated Formic Acid

Direct formic acid fuel cells (DFAFC) are considered one of the most promising fuel cells to penetrate the market due to their desired and unique properties. Formic acid (FA) could be easily produced from different sources (especially biomass) and is non-toxic. The FA-based fuel cell has a high open circuit potential in comparison to methanol and Ethanol1, high energy conversion efficiency, and fast kinetics. However, the major drawback that affects using DFAFCs is the catalysts' stability and reaction intermediates' poisoning effect, especially at high concentrations of FA.FA has a dual pathway mechanism: either the simple and desired pathway of direct oxidation to CO2 2 or the unfavorable indirect oxidation to poisonous CO-like species that strongly adsorb on the catalyst surface, deactivating it,3 before it is hardly oxidized in a second step to give CO2. Therefore, the catalyst should be designed to direct the reaction towards the direct pathway and facilitate the poisoning species removal. The most active catalyst for FA oxidation in acidic media is palladium4 but it is highly susceptible to CO poisoning, especially as the FA concentration increases due to the high contribution of the indirect pathway. In addition, palladium nanoparticles supported on carbon material are known to suffer from dissolution in the acidic media making the electrode unstable for long-term application.5 In this presentation, the synthesis of nonstoichiometric WOx nanorods using hydrothermal methods will be reported. The Pd nanoparticles are synthesized and loaded on the WOx nanorods using ethanol as both a solvent and a reducing agent to produce a surfactant-free Pd surface. The synthesized materials are evaluated using XRD, TEM, FT-IR, EDS, and XPS. The effect of WOx nanorods as catalyst support on Pd nanoparticles activity and stability towards the oxidation of different concentrations (1-4 M) of FA in acidic media are evaluated using cyclic voltammetry (CV) and chronopotentiometry (CP), and compared with that of carbon-supported Pd catalyst. The Pd behavior in both cases will be correlated to its chemical and physical properties and thoroughly discussed.

Design of Pt-Sn-Zn Nanomaterials for Successful Methanol Electrooxidation Reaction.

This work highlights the potential for the synthesis of new PtSnZn catalysts with enhanced efficiency and durability for methanol oxidation reaction (MOR) in low-temperature fuel cells. In this research, PtZn and PtSnZn nanoparticles deposited on high surface area Vulcan XC-72R Carbon support were created by a microwave-assisted polyol method. The electrochemical performances of synthesized catalysts were analyzed by cyclic voltammetry and by the electrooxidation of adsorbed CO and the chronoamperometric method. The physicochemical properties of obtained catalysts were characterized by transmission electron microscopy (TEM), thermogravimetric (TGA) analysis, energy dispersive spectroscopy (EDS) and by X-ray diffraction (XRD). The obtained findings showed the successful synthesis of platinum-based catalysts. It was established that PtSnZn/C and PtZn/C catalysts have high electrocatalytic performance in methanol oxidation reactions. Catalysts stability tests were obtained by chronoamperometry. Stability tests also confirmed decreased poisoning and indicated improved stability and better tolerance to CO-like intermediate species. According to activity and stability measurements, the PtSnZn/C catalyst possesses the best electrochemical properties for the methanol oxidation reaction. The observed great electrocatalytic activity in the methanol oxidation reaction of synthesized catalysts can be attributed to the beneficial effects of microwave synthesis and the well-balanced addition of alloying metals in PtSnZn/C catalysts.

Effect of MoO3 on Pd nanoparticles for efficient formic acid electrooxidation

Palladium is a promising formic acid electro-oxidation (FAO) catalyst due to its higher initial activity than platinum. However, suffering from the adsorption of hydrogen and CO-like species, the activity and stability of Pd are still unsatisfied. Herein, palladium nanoparticles deposited on carbon supported molybdenum trioxide (Pd–MoO3/C) is prepared with MoO3 as the promoter for FAO. X-ray photoelectron spectroscopy analysis proves the close contact between Pd and MoO3, which generates the hydrogen spillover effect and forms the Pd–Mo structure. The hydrogen spillover effect enhances the desorption of hydrogen from Pd and facilitates the FAO activity. Both the spillover effect and Pd–Mo structure contribute to the removal of COad and facilitate the durability and anti-CO poisoning ability of the catalyst. With the optimized ratio of MoO3 to carbon black, the Pd–MoO3/C-20 catalyst owns the best specific activity of 5.86 mA cm−2, which is 1.86 times of Pd/C.

Electrochemistry of ethanol and dimethyl ether at a Pt electrode in a protic ionic liquid: the electrode poisoning mechanism.

A protic ionic liquid (PIL), N,N-diethyl-N-methyl ammonium trifluoromethane sulfonate, [dema][TfO] was synthesized and confirmed using 1H-NMR and ion chromatography (IC). The surface electrocatalysis of ethanol (EtOH) and dimethyl ether (DME) was investigated on a polycrystalline Pt electrode in a PIL using a cyclic voltammetry technique. The voltammetry response shows that surface Pt-oxides/hydroxides (PtOH/PtO) are formed due to the oxidation of trace water (240 ppm determined by coulometric Karl-Fischer (FT) titration) in [dema][TfO] which plays a pivotal role during the electrocatalytic oxidation of EtOH and DME in the PIL. Oxidation of EtOH and DME coincides with coverage of the Pt surface by the adsorbed oxide species that helps to activate both processes by oxidizing the adsorbed poisoning CO and CO-like intermediate species via a 'bifunctional' reaction mechanism. The influence of temperature was investigated to obtain quantitative and qualitative information on the kinetics of EtOH oxidation. Higher activation energies are measured for EtOH oxidation in [dema][TfO] than in aqueous electrolytes due to the low water content and high viscosity of the PIL. This study gave a basic insight into the mechanism of EtOH and DME oxidation reactions, and the Pt-electrode poisoning species formation mechanism in the neoteric electrolyte medium is electrochemically investigated and reported.

Electro-Design of Bimetallic PdTe Electrocatalyst for Ethanol Oxidation: Combined Experimental Approach and Ab Initio Density Functional Theory (DFT)-Based Study.

An alternative electrosynthesis of PdTe, using the electrochemical atomic layer deposition (E-ALD) method, is reported. The cyclic voltammetry technique was used to analyze Au substrate in copper (Cu2+), and a tellurous (Te4+) solution was used to identify UPDs and set the E-ALD cycle program. Results obtained using atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques reveal the nanometer-sized flat morphology of the systems, indicating the epitaxial characteristics of Pd and PdTe nanofilms. The effect of the Pd:Te ratio on the crystalline structure, electronic properties, and magnetic properties was investigated using a combination of density functional theory (DFT) and X-ray diffraction techniques. Te-containing electrocatalysts showed improved peak current response and negative onset potential toward ethanol oxidation (5 mA; −0.49 V) than Pd (2.0 mA; −0.3 V). Moreover, DFT ab initio calculation results obtained when the effect of Te content on oxygen adsorption was studied revealed that the d-band center shifted relative to the Fermi level: −1.83 eV, −1.98 eV, and −2.14 eV for Pd, Pd3Te, and Pd3Te2, respectively. The results signify the weakening of the CO-like species and the improvement in the PdTe catalytic activity. Thus, the electronic and geometric effects are the descriptors of Pd3Te2 activity. The results suggest that Pd2Te2 is a potential candidate electrocatalyst that can be used for the fabrication of ethanol fuel cells.

Enhancing Ethanol Electrooxidation Stability over PtIr/GN Catalysts by In Situ Formation of IrO2 at Adjacent Sites

PtIr alloy is considered as one of the most promising catalysts for ethanol electrooxidation due to its excellent C–C bond breaking and dehydrogenation abilities. However, a small amount of intermediate species produced by ethanol oxidation can still poison Pt, thereby affecting the stability of ethanol oxidation. Here, graphene supported PtIr nanoparticles (PtIr/GN) with a Pt: Ir atomic ratio of 3:1 is synthesized by a simple hydrothermal reduction and thermal annealing. The physicochemical analyses show that IrO2 is formed in situ in PtIr/GNs (O) during annealing and located adjacent to PtIr alloys. IrO2 and PtIr are evenly dispersed on GNs. The electrochemical results indicate that PtIr/GNs (O) has higher catalytic activity and stability for ethanol electrooxidation than PtIr/GNs. After 1000 voltammetric cycles, the peak current density for PtIr/GNs (O) is 2.5 times higher than that for PtIr/GNs. The outstanding electrochemical performance of PtIr/GNs (O) is derived from PtIr alloy that promotes the cleavage of the C–C bond and weakens the adsorption of Pt to intermediate species, IrO2 that improves the tolerance of Pt to CO-like species and enhances the structural stability of Pt, and PtIr alloy and IrO2 in adjacent positions that synergistically improve the stability of catalytic ethanol oxidation.

Chain-like PtPd nanoparticles with a long-time stability as an efficient electrocatalyst for alcohols oxidation reaction

In this study, chain-like PtPd/PVA catalysts were synthesized by a two-step hydrothermal method with the assistance of polyvinyl alcohol as a green reducing agent, structure guiding agent, dispersing agent, and binder. Among all the catalysts, Pt1Pd5/PVA catalyst shows the highest mass activity (3774.2 mA mgpt−1) for methanol oxidation reaction. Also, the residual activity of Pt1Pd5/PVA catalyst after chronoamperometry (CA) test of 28 h is close to that of commercial Pt/C after CA test of 5000 s. The excellent electrocatalytic activity of Pt1Pd5/PVA catalyst is mainly attributed to the synergistic effect between Pt and Pd. This can optimize the surface electronic structure and reduce the adsorption of CO-like species over the Pt surface. Besides, the unique chain network structure of PtPd forms a conductive network of self-conducting electrons. At the same time, a large amount of PVA causes an ultra-long stability through the coating of PtPd catalyst by PVA and the interaction with PVA and PtPd. This work contributes a facile and clean method for the synthesis of stable and efficient precious metal alloy catalysts for alcohols oxidation reaction.

Surface Poisoning Induced By PGM-Based Catalyst Degradation in Alkaline Media and Self-Recovery By "CO-like" Stripping

Fuel cells are advanced CO2 emission-free generators that are currently used for automobiles. Since the cost of platinum group metal (PGM) catalysts for both hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) is too high, switching to alkaline fuel cells (AFCs) is necessary. However, the alkaline media is much more challenging for HOR since extra energy is required to generate proton from hydroxide anion [1]. In addition, the alkaline durability of PGM/C catalysts is not granted, because Pt assists the local carbon corrosion, by promoting oxidation of “CO-like species”, leading to CO2 and carbonates formation, and finally particles detachment [2]. Lower degradation rate for Pd/C was measured compared to Pt/C in neutral (Ar) or reducing (H2) environment [3-5].This work is an in-depth investigation on the differences between Pt/C and Pd/C in alkaline during AST in H2 (0-0.5 VRHE at 100 mV/s, for 1000 CVs). Figure 1 shows that prolonged cycling in this low potential region in reducing atmosphere induces “poisoning” of the PGM NPs surface by “CO-like species”; one cleaning method to recover the ECSA of Pt and Pd, is to simply strip these “CO-like species” by cycling the potential at higher values, as shown by Castanheira, et al. on Pt/C [6]. Comparing electrochemistry results and IL-TEM images suggests that stripping the “CO-like species” is a reversible process for the remaining particles that are still intact on the carbon substrates. Another cleaning method is to apply 500 CVs, from 0-1 VRHE, at 100 mV/s in Ar inert gas (Ar cleaning method). This method gives higher recovering percentage comparing to the “CO-like species” stripping one and is considered to be a better cleaning method. The reversible ECSA percentage for the catalysts from the Ar cleaning methods were calculated to be 11 % wrt. the initial ECSA of Pt/C and 14% wrt. the initial ECSA of Pd/C. Finally, the overall ECSA loss of Pt/C after cleaning was 46% (wrt. initial ECSA) while Pd/C’s case was only 8%: so, Pt assists the C corrosion better than Pd. Moreover, Pt is easy to be poisoned and is not as reversible as Pd.

Rational one-pot synthesis of ternary PtIrCu nanocrystals as robust electrocatalyst for methanol oxidation reaction

Development of self-assembled nanoarchitectures of tailored morphology and composition for diversified applications have received great interest in the last decades. Pt-based nanocrystals (NCs) exhibited enhanced catalytic performance towards different applications specially as electrocatalysts for fuel cells. Herein, ternary PtIrCu nanocrystals (NCs) were prepared via one-pot synthesis procedure and employed as electrocatalyst for methanol oxidation reaction (MOR) in acid medium. The as-prepared ternary NCs exhibited mass activity of 863 mA mg−1 which is almost 1.5, 2.2, and 6.0 times more greater than that of PtCu, PtIr, and Pt/C, respectively. Additionally, after stability test for 1000 s, the retained current density on PtIrCu NCs was 13.6 times higher than that on Pt/C. The enhanced catalytic activity and durability of ternary PtIrCu NCs compared to PtCu, PtIr, and Pt/C was assigned to the strain and electronic effects which enhance the oxidation kinetics and enhance the poisoning tolerance towards CO-like intermediate species.

Green dual-template synthesis of AgPd core–shell nanoparticles with enhanced electrocatalytic activity

A key challenge in developing an ethanol oxidation reaction is nontoxic fabrication of highly active stable and low-cost catalysts. Here we design a green synthetic strategy of AgPd bimetallic nanosphere by a dual-template cascade method. The Pd nanoshell is firstly prepared using Vapreotide acetate as a primary template, and then the Ag nanoshell acts as a secondary template for the distribution of AgPd alloy nanoparticles. The AgPd nanoparticles have core–shell structures and various sizes, and their shell thicknesses are tuned by controlling the amount of PdCl2. The six different samples are prepared, named AgPd-1, AgPd-2, AgPd-3, AgPd-4, AgPd-5, and AgPd-6, respectively. The mass current density of AgPd-5, is higher 3.87 times that of commercial Pd/C, and exhibits the best ethanol oxidation reaction activity and long-term stability. The main reasons are that the AgPd-5 possessed excellent specific surface area due to their rough structure, and Ag can remove more CO-like species. This is the first time a Vapreotide acetate/Ag-template method has been used to synthesize a AgPd core–shell structure, which would have broad application prospects for direct ethanol fuel cells.

Highly stable Pt/ITO catalyst as a promising electrocatalyst for direct methanol fuel cells

Direct methanol fuel cells (DMFCs) have attracted considerable scientific interest because of their ease of operation and implementation; however, poor electrocatalytic activity and durability are the main hindrances for their commercial feasibility. Moreover, the deactivation of active Pt sites, due to the coverage of CO-like species during the electrochemical oxidation reaction, significantly degrades the electrochemical surface area (ECSA). In the present work, stable Pt-supported tin-modified indium oxide (ITO) was synthesized as a promising electrocatalyst towards the methanol oxidation reaction (MOR) in DMFCs. It was found that 20 wt% Pt/ITO yielded much higher current density (∼0.71 mA/cm 2 ) than the state-of-the-art carbon-supported Pt (E-TEK) electrocatalyst. Furthermore, the I f / I b ratio, which featured the CO tolerance of the electrocatalyst, of 20 wt% Pt/ITO was found to be ∼1.42, which is ∼1.5-fold higher than that of 20 wt% Pt/C (E-TEK). Chronoamperometry results indicated that 20 wt% Pt/ITO manifested much higher stability than 20 wt% Pt/C (E-TEK).

4A Zeolite Support for Pt Nanoparticles towards Methanol Oxidation

The effect of 4A zeolite as a support on the electrocatalytic activity of Pt nanoparticles for the oxidation of methanol has been investigated. Pt/4A zeolite and Pt/C catalysts with the same mass of Pt are prepared by loading the Pt nanoparticles stabilized by PEG-400 on 4A zeolite and carbon black, respectively. Physical analyses reveal unevenly distributed but no large agglomerates of the Pt nanoparticles on the surface of 4A zeolite due to PEG-400 attached to the Pt nanoparticles, while the Pt nanoparticles on carbon black show a uniform distribution and a lesser degree of agglomeration. However, Pt/4A zeolite shows a much more negative onset potential and a significantly higher peak current density than Pt/C in methanol oxidation in both acidic and alkaline solutions. Pt/4A zeolite also shows high resistance to the poisoning caused by CO-like species formed in the reaction. The results indicate that 4A zeolite is superior to carbon black as a support for the Pt nanoparticles toward methanol oxidation, and further suggest that some types of zeolites could be used as efficient support materials in electrocatalysis.

Cobalt oxyhydroxide and carbon dots modified by platinum as superior electrocatalyst for methanol oxidation

The engineering of electrocatalysts with high performance for methanol oxidation reaction (MOR) is of great urgency for the development of direct methanol fuel cells (DMFCs). Here, we designed and fabricated cobalt oxyhydroxide and carbon dots modified by platinum (Pt-CoOOH-CDs/C) hybrids with low content of Pt (13 wt%) as electrocatalyst, which exhibit high activity (856.3 mA·mg−1Pt), stability (3 h) and better anti-poisoning ability for MOR. The Pt-CoOOH-CDs/C was synthesized by precipitate method followed with photochemical deposition. In the catalytic system, the Pt nanoparticles serve as the active center toward MOR, CoOOH-CDs use as the co-catalyst to oxidize CO-like poisonous species to CO2 on neighbouring Pt sites, and the cost-efficient carbon black enhances the conductivity for the system. The cost-efficient Pt-CoOOH-CDs/C system with improved kinetics for anodic methanol oxidation has promising application in alkaline DMFCs.

Efficient Direct Formic Acid Fuel Cells (DFAFCs) Anode Derived from Seafood waste: Migration Mechanism

Commercial Pt/C anodes of direct formic acid fuel cells (DFAFCs) get rapidly poisoned by in-situ generated CO intermediates from formic acid non-faradaic dissociation. We succeeded in increasing the Pt nanoparticles (PtNPs) stability and activity for formic acid oxidation (DFAFCs anodic reaction) by embedding them inside a chitosan matrix obtained from seafood wastes. Atop the commercial Pt/C, formic acid (FA) is predominantly oxidized via the undesired poisoning dehydration pathway (14 times higher than the desired dehydrogenation route), wherein FA is non-faradaically dissociated to CO resulting in deactivation of the majority of the Pt active-surface sites. Surprisingly, PtNPs chemical insertion inside a chitosan matrix enhanced their efficiency for FA oxidation significantly, as demonstrated by their 27 times higher stability along with ~400 mV negative shift of the FA oxidation onset potential together with 270 times higher CO poisoning-tolerance compared to that of the commercial Pt/C. These substantial performance enhancements are believed to originate from the interaction of chitosan functionalities (e.g., NH2 and OH) with both PtNPs and FA molecules improving FA adsorption and preventing the PtNPs aggregation, besides providing the required oxygen helping with the oxidative removal of the adsorbed poisoning CO-like species at low potentials. Additionally, chitosan induced the retrieval of the Pt surface-active sites by capturing the in-situ formed poisoning CO intermediates via a so-called “migration mechanism”.

Effect of Ni addition on electrocatalytic activity of PdCu catalysts for ethanol electrooxidation: An experimental and theoretical study

A facile and clean electrochemical method has been developed for the synthesis of ternary PdCuNi catalysts on the surface of carbon Vulcan. The composition and morphology of the PdCuNi/C were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), X‒ray diffraction (XRD), EDX element mapping and transmission electron microscopy (TEM). The effect of Cu and Ni on the electrochemical activity of ternary PdCuNi alloy electrocatalysts was investigated for ethanol oxidation reaction (EOR). Between the different compositions, Pd35%Cu14%Ni2%/C catalyst exhibits superior mass activity which is about 10 times higher than that of commercial Pd/C catalyst. The onset peak potential for ethanol oxidation on Pd35%Cu14%Ni2%/C catalyst shifts to lower potential than that of PdCu/C and Pd/C catalysts. The stability tests revealed that the existing of Cu combined with Ni can improve the poison tolerance of Pd/C catalyst by removal of adsorbed CO-like intermediate species during ethanol oxidation. The experimental work is further investigated by theoretical study based on DFT-D calculations. The experimental and theoretical results exhibited similar trends in electrocatalytic activity of catalyst composition; indicating ternary PdCuNi alloys could be a promising anode catalyst for direct ethanol fuel cells.

Efficient direct formic acid fuel cell (DFAFC) anode of nano-sized palladium complex: High durability and activity origin

The low stability of Pd-based catalysts extremely obstructs their applied application in the direct formic acid fuel cells (DFAFCs). Herein, a novel nano-sized palladium-complex (nano-Pdcomplex) with outstanding performance (activity and durability) for DFAFCs anodic reaction (Formic acid oxidation; FAO) compared to the commercial Pd-based catalysts is introduced. Morphologically, nano-sized Pd-complex shows an intersected nano-rod like structure with an average particle size ca. 17nm. Electrochemically, nano-Pdcomplex modified GC electrode (Nano-Pdcomplex/GC) has 12 times higher electrocatalytic activity, 8.0 times higher electrochemical active surface area, 3.0 times higher catalyst utilization, and ca., 16 times higher stability after 5.0h than that of traditional Pd nanoparticles modified GC electrode (PdNPs/GC) with the same Pd loading. This significant enhancement in both activity and stability is attributed to nano-Pdcomplex bulky structure hindering the agglomeration of the Pd active sites and inhibiting the adsorption of poisoning CO-like intermediate species. DFT studies shows that nano-Pdcomplex has two different geometries: (a) cis-structure which has a square planar geometry and it is inactive for FAO, and (b) trans-structure with a tetrahedral geometry and it is highly active for FAO. This study introduces a new promising category of Pd-based catalyst with high activity, catalyst utilization and durability for DFAFCs applications.

Electrochemical and in situ FTIR study of the ethanol oxidation reaction on PtMo/C nanomaterials in alkaline media

In this work, the catalytic activity of PtMo/C catalysts for the Ethanol Oxidation Reaction (EOR) in 0.5molL−1 KOH electrolyte was evaluated by electrochemical and in situ Fourier Transform Infrared Spectroscopy (FTIR) measurements. The alloys having 1:1, 2:1 and 3:1 Pt:Mo atomic ratios were synthesized by the formic acid method. X-ray diffraction analyses (XRD) showed the crystalline features of the catalysts, with crystallite sizes between 2.5 and 3.2nm. Cyclic voltammograms (CVs) indicated the alloys mass catalytic activity in the order: Pt1Mo1/C>Pt3Mo1/C>Pt2Mo1/C, in all cases higher that Pt/C. For specific catalytic activity, the performance was in the order Pt3Mo1/C>Pt1Mo1/C–Pt/C>Pt2Mo1/C. Two CO-like species namely COadsI and COadsII were evidenced from CO-stripping measurements on the alloys. In situ FTIR characterization showed that the alloys promote the oxidation of ethanol in the alkaline media mainly through a 4 electrons transfer route. CO2 was produced probably from the break-up of the CC bond and the oxidation of C1 species. Pt3Mo1/C produced moreCOadsI, followed by Pt1Mo1/C, oxidizing carbon monoxide more easily. These two alloys also had a higher CO2/CH3CHO ratio, due to a high efficiency for oxidizing C2 and C1 species to CO2. Such capabilities promoted a higher catalytic activity of Pt1Mo1/C and Pt3Mo1/C for the EOR, related to the other catalysts.

Pt/CN-doped electrocatalysts: Superior electrocatalytic activity for methanol oxidation reaction and mechanistic insight into interfacial enhancement

Nitrogen-doped ordered mesoporous carbon (NOMC) is studied as the support to synthesize a Pt/CN-doped catalyst for methanol oxidation reaction (MOR). The effects of carbon dimension and metal loading are investigated by nitrogen ad/desorption isotherms, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical methods. Both TEM and XRD results show that platinum nanoparticles (Pt NPs) are highly dispersed on NOMC with a uniform and narrow distribution, while the dimension of NOMC has a considerable effect on the dispersion of Pt. For 10wt% metal loading, the average diameter of Pt NPs on 2D-NOMC is 1.40nm; smaller than that on 3D-NOMC (1.90nm). XPS results reveal that a strong electronic interaction exists between Pt and NOMC, indicating the formation of Pt–N bonds at the interface. Such an interaction gets more pronounced in the case of low Pt loadings and low-dimensional supports; the reason is that the 2D support is more accessible to load Pt and the metal-support interface is better developed at low metal loadings.The electrochemical results are well correlated with the physiochemical characterizations. 1) The electrochemically active surface area of Pt is higher on the 2D-support than that on the 3D-one, confirming the better dispersion of Pt on NOMC-2D. 2) A positive shift in the potential is observed for the adsorption of oxygen-containing species onto Pt, which is indicative of the charge transfer from Pt to the support and the formation of Pt–N bonds. 3) Both onset and peak potentials are negatively shifted by ca. 50mV for MOR on 10wt% Pt/NOMC-2D, as compared with the commercial Pt/XC-72. The ratio of forward to backward current, a measure of poisoning tolerance, is 1.1 on Pt/NOMC-2D and 0.80 on Pt/XC-72R. This enhancement can be attributed to the bifunctional mechanism at the Pt/CN-doped interface. In MOR, CO-like intermediate species on Pt can be effectively stripped off by the adjacent active –OH species on carbon, generated at lower potentials.

Photo-excited in situ loading of Pt clusters onto rGO immobilized SnO2 with excellent catalytic performance toward methanol oxidation

Maximizing the surface area and the exposed active sites of Pt-based catalysts is one of the most effective strategies to improve their electrocatalytic performance. We here present an environmentally friendly construction of a two-dimensional Pt/SnO2/reduced-graphene-oxide (rGO) nanocomposite as a active and durable electrocatalyst. Initially, liquid-phase laser ablation generated highly reactive SnOx nanoparticles (NPs) were used as a precursor to transform the graphene oxide into rGO. Simultaneously, the initial amorphous-like SnOx can further crystallize into SnO2 NPs, which were uniformly anchored onto rGO sheets. Subsequently, the electrons photo-excited from semiconductor SnO2 were used as green reducing agents, which can in situ reduce the PtCl62+ ions to form ultrafine Pt NPs with an average size of about 1–2nm that uniformly dispersed onto SnO2 NPs. Compared with Pt/rGO catalysts without SnO2 modification, the Pt/SnO2/rGO hybrid ternary catalysts not only show larger electrochemical active surface area and higher catalytic activity toward methanol oxidation, but also exhibit better long-term cycle stability and better tolerance toward CO-like species. Such significantly enhanced electrochemical performance could be attributed to the uniformly dispersed fine Pt NPs and the synergetic effect from the hybrid noble metal-semiconductor-carbon network components.