Efficient and stable PtFe alloy catalyst for electrocatalytic methanol oxidation with high resistance to CO

Direct methanol fuel cells(DMFC) are widely considered to be an ideal green energy conversion device but their widespread applications are limited by the high price of the Pt-based catalysts and the instability in terms of surface CO toxicity in long-term operation.Herein,the PtFe alloy nanoparticles(NPs) with small particle size(~4.12 nm) supported on carbon black catalysts with different Pt/Fe atomic ratios(Pt_(1)Fe_(2)/C,Pt_(3)Fe_(4)/C,Pt_(1)Fe_(1)/C,and Pt_(2)Fe_(1)/C) are successfully prepared for enhanced anti-CO poisoning during methanol oxidation reaction(MOR).The optimal atomic ratio of Pt/Fe for the MOR is 1:2,and the mass activity of Pt_(1)Fe_(2)/C(5.40 A mg_(Pt)^(-1)) is 13.5 times higher than that of conventional commercial Pt/C(Pt/C-JM)(0.40 A mg_(Pt)^(-1)).The introduction of Fe into the Pt lattice forms the PtFe alloy phase,and the electron density of Pt is reduced after forming the PtFe alloy.In-situ Fourier transform infrared results indicate that the addition of oxyphilic metal Fe has reduced the adsorption of reactant molecules on Pt during the MOR.The doping of Fe atoms helps to desorb toxic intermediates and regenerate Pt active sites,promoting the cleavage of C-O bonds with good selectivity of CO_(2)(58.1%).Moreover,the Pt_(1)Fe_(2)/C catalyst exhibits higher CO tolerance,methanol electrooxidation activity,and long-term stability than other Pt_(x)Fe_(y)/C catalysts.

Precision tuning of highly efficient Pt-based ternary alloys on nitrogen-doped multi-wall carbon nanotubes for methanol oxidation reaction

The electrochemical methanol oxidation is a crucial reaction in the conversion of renewable energy.To enable the widespread adoption of direct methanol fuel cells(DMFCs),it is essential to create and engineer catalysts that are both highly effective and robust for conducting the methanol oxidation reaction(MOR).In this work,trimetallic PtCoRu electrocatalysts on nitrogen-doped carbon and multi-wall carbon nanotubes(PtCoRu@NC/MWCNTs)were prepared through a two-pot synthetic strategy.The acceleration of CO oxidation to CO_(2) and the blocking of CO reduction on adjacent Pt active sites were attributed to the crucial role played by cobalt atoms in the as-prepared electrocatalysts.The precise control of Co atoms loading was achieved through precursor stoichiometry.Various physicochemical techniques were employed to analyze the morphology,element composition,and electronic state of the catalyst.Electrochemical investigations and theoretical calculations confirmed that the Pt_(1)Co_(3)Ru_(1)@NC/MWCNTs exhibit excellent electrocatalytic performance and durability for the process of MOR.The enhanced MOR activity can be attributed to the synergistic effect between the multiple elements resulting from precisely controlled Co loading content on surface of the electrocatalyst,which facilitates efficient charge transfer.This interaction between the multiple components also modifies the electronic structures of active sites,thereby promoting the conversion of intermediates and accelerating the MOR process.Thus,achieving precise control over Co loading in PtCoRu@NC/MWCNTs would enable the development of high-performance catalysts for DMFCs.

Bimetallic Pt–Ru covalently bonded on carbon nanotubes for efficient methanol oxidation

Platinum-based nanocomposites have been considered as one of the most promising catalysts for methanol oxidation reactions(MORs), which yet still suffer from low electrochemical activity and electron-transfer properties. Apart from van-der-Waals heterostructures,herein, we report a novel nanocomposite with the structure of Pt–Ru bimetallic nanoparticles covalently-bonded onto multi-walled carbon nanotubes (MWCNTs)(Pt–Ru@MWCNT), which have been successfully fabricated via a facile and green synthesis method. It is demonstrated that the Pt–Ru@MWCNT nanocomposite possesses much enhanced electrocatalytic activity with the electrochemical active surface area(ECSA) of 110.4 m^(2)·g^(-1)for Pt towards MOR, which is 2.67 and 4.0 times higher than those of 20wt%commercial Pt@C and Pt-based nanocomposite prepared by other method, due to the improved electron-transfer properties originated from M–O–C covalent bonds. This work provides us a new strategy for the structural design of highly-efficient electrocatalysts in boosting MOR performance.

Research advances in unsupported Pt-based catalysts for electrochemical methanol oxidation

Direct methanol fuel cells are one of the most promising alternative energy technologies in the foreseeable future, but its successful commercialization in large scale is still heavily hindered by several technical shortfalls, especially the undesirable activity and durability issues of electrocatalysts toward methanol oxidation reaction. In light of these challenges, the inherent advantages of unsupported Pt based nanostructures demonstrate their great potentials as durable and efficient electrocatalysts for direct methanol fuel cells. This review will summarize recent achievements of unsupported Pt-based electrocatalysts toward methanol oxidation, with highlighting the interactions between the performance and structure tailoring and composition modulating. At last, a perspective is proposed for the upcoming challenges and possible opportunities to further prompt the practical application of unsupported Pt-based electrocatalysts for direct methanol fuel cells.

Effects of CeO_(2)pre-calcined at different temperatures on the performance of Pt/CeO_(2)-C electrocatalyst for methanol oxidation reaction

Pt/CeO_(2)-C catalysts with CeO_(2)pre-calcined at 300-600 ℃were synthesized by combining hydrothermal calcination and wet im-pregnation.The effects of the pre-calcined CeO_(2)on the performance of Pt/CeO_(2)-C catalysts in methanol oxidation were investigated.The Pt/CeO_(2)-C catalysts with pre-calcined CeO_(2)at 300-600 ℃showed an average particle size of 2.6-2.9 nm and exhibited better methanol elec-tro-oxidation catalytic activity than the commercial Pt/C catalyst.In specific,the Pt/CeO_(2)-C catalysts with pre-calcined CeO_(2)at 400 ℃dis-played the highest electrochemical surface area value of 68.14 m2·g−1 and If/Ib ratio(the ratio of the forward scanning peak current density(If)and the backward scanning peak current density(Ib))of 1.26,which are considerably larger than those(53.23 m2·g−1 and 0.79,respectively)of the commercial Pt/C catalyst,implying greatly enhanced CO tolerance.

Ultrafine Pt nanoparticles supported on double-shelled C/TiO2 hollow spheres material as highly efficient methanol oxidation catalysts

Catalyst support is extremely important for future fuel cell devices.In this work,we developed doubleshelled C/TiO2(DSCT)hollow spheres as an excellent catalyst support via a template-directed method.The combination of hollow structure,TiO2 shell and carbon layer results in excellent electron conductivity,electrocatalytic activity,and chemical stability.These uniformed DSCT hollow spheres are used as catalyst support to synthesize Pt/DSCT hollow spheres electrocatalyst.The resulting Pt/DSCT hollow spheres exhibited high catalytic performance with a current density of 462 mA mg^-1 for methanol oxidation reaction,which is 2.52 times higher than that of the commercial Pt/C.Furthermore,the increased tolerance to carbonaceous poisoning with a higher If/Ibratio and a better long-term stability in acid media suggests that the DSCT hollow sphere is a promising C/TiO2-based catalyst support for direct methanol fuel cells applications.

Rational design ternary platinum based electrocatalysts for effective methanol oxidation reaction

Exploring effective, durable, and affordable electrocatalysts of methanol oxidation reaction(MOR) is of vital significance for the industrial application of direct methanol fuel cells. Herein, an efficient, general,and expandable method is developed to synthesis two-dimensional(2D) ternary Pt Bi M nanoplates(NPLs), in which various M(Co, Ni, Cu, Zn, Sn) is severed as the third component to the binary Pt Bi system. The MOR performance of Pt Bi M NPLs is entirely investigated, demonstrating that both the MOR activity and durability is enhanced with the introduction of the additional composition. Pt3Bi3Zn NPLs shows much higher MOR activity and stability than that of the Pt Bi counterparts, not to mention the current advanced Pt Ru/C and Pt/C catalysts. The prominent performances are attributed to the modulated electronic structure of the surface Pt in Pt Bi NPLs by the addition of Zn, resulting in a weakened affination between Pt and the adsorbed poisoning species(mainly CO) compared with Pt Bi NPLs, verified by density functional theory(DFT) calculations. In addition, the absorbed OH can be generated on the surface of Zn atom due to its favorable water activation properties, thus the CO removal on the adjacent Pt atoms is accelerated, further leading to a high activity and anti-poisoning performance of the resulting Pt_(3)Bi_(3)Zn catalyst. This work provides new insights and robust strategy for highly efficient MOR electrocatalyst with extraordinary anti-poisoning performance and stability.

Controllable synthesis of grain boundary-enriched Pt nanoworms decorated on graphitic carbon nanosheets for ultrahigh methanol oxidation catalytic activity

Although one-dimensional Pt nanocrystals have long been regarded as ideal electrode catalysts for fuel cells,the synthetic techniques commonly involve the use of various complicated templates or surfactants,which have largely hampered their large-scale industrial application.Herein,we present a convenient and cost-effective approach to the stereoassembly of quasi-one-dimensional grain boundary-enriched Pt nanoworms on nitrogen-doped low-defect graphitic carbon nanosheets(Pt NWs/NL-CNS).Benefiting from its numerous catalytically active grain boundaries as well as optimized electronic structure,the as-derived Pt NWs/NL-CNS catalyst possesses exceptionally good electrocatalytic properties for methanol oxidation,including an ultrahigh mass activity of 1949.5 mA mg^(-1), reliable long-term durability,and strong poison tolerance,affording one of the most active Pt-based electrocatalysts for methanol oxidation reaction.Density functional theory calculation further reveals that the formation of worm-shape Pt morphology is attributed to the modified electronic structure as well as controllable defect density of the carbon matrix,which could also weaken the adsorption ability of Pt towards CO molecule and meanwhile synergistically promotes the catalytic reaction kinetics.

Platinum nanoparticles coated by graphene layers: A low-metal loading catalyst for methanol oxidation in alkaline media

Platinum catalysts play a major role in the large scale commercialization of direct methanol fuel cells(DMFC).Here,we present a procedure to create a nanostructural graphene-platinum(Gr Pt)composite containing a small amount(5.3 wt%)of platinum nanoparticles coated with at least four layers of graphene.The composite,as Gr Pt ink,was deposited on a glassy carbon electrode and its electrocatalytic activity in a methanol oxidation reaction(MOR)was evaluated in a 1 M CH3OH/1 M NaOH solution.The results indicated an enhanced catalytic performance of GrPt towards MOR in alkaline media compared with the Pt/C material.Electron energy-loss spectroscopy and X-ray photoelectron spectroscopy(recorded before and after the electrochemical assays)were employed to analyze the changes in the chemical composition of the nanomaterial and to explain the transformations that took place at the electrode surface.Our findings suggest that growing of graphene on platinum nanoparticles improve the catalytic performance of platinum-graphene composites towards MOR in alkaline media.

Robust copper nanocrystal/nitrogen-doped carbon monoliths as carbon monoxide-resistant electrodes for methanol oxidation reaction

Noble metal-based electrocatalysts present high activities for methanol oxidation reaction(MOR),but are limited by their high cost,low stability and poor resistance to carbon monoxide(CO) poisoning.The development of active and stable non-noble metal electrocatalysts for MOR is desired,but remains a challenge.Herein,we report a simple strategy to make copper nanocrystal/nitrogen-doped carbon(Cu/N-C)monoliths,which can serve as active and robust electrodes for MOR.Copper nanocrystals were electrochemically deposited onto a conductive polyaniline hydrogel and calcined to form Cu/N-C monolith,where the active copper nanocrystals are protected by nitrogen-doped carbon.Owing to their extremely high electrical conductivity(1.25 × 10^(5) S cm^(-1)) and mechanical robustness,these Cu/N-C monoliths can be directly used as electrodes for MOR,without using substrates or additives.The optimal Cu/N-C(FT)@500 monolith shows a high MOR activity of 189 mA cm^(-2) at 0.6 V vs.SCE in alkaline methanol solution,superior to most of reported Cu-based MOR catalysts.Cu/N-C(FT)@500 also presents a better stability than Pt/C catalyst in the long-term MOR test at high current densities.Upon carbon monoxide(CO) poisoning,Cu/N-C(FT)@500 retains 96% of its MOR activity,far exceeding the performance of Pt/C catalyst(61% retention).Owing to its facile synthesis,outstanding activity,high stability and mechanical robustness,Cu/N-C(FT)@500 monolith is promising as a low-cost,efficient and CO-resistant electrocatalyst for MOR.

Methanol Oxidation over TiO_2-modified Multi-walled Carbon Nanotubes Supported Pt-Mo Electrocatalyst

In order to develop a novel and high-performance catalytic material for direct methanol fuel cells（DMFC）, molybdenum oxide as a co-catalyst with Pt on multi-walled carbon nanotubes which were modified by titanium dio-xide（denoted as CNTs@TiO2） was investigated. The physicochemical characterizations of the catalysts were carried out via X-ray diffraction（XRD）, transmission electron microscopy（TEM） and X-ray photoelectron spectroscopy（XPS）. Cyclic voltammetry（CV） showed that the CO-tolerance performance increased in the sequence of Pt/CNTs Pt/CNTs@TiO2Pt-Mo/CNTs@TiO2. The improved CO-tolerance performance of the Pt-Mo/CNTs@TiO2 catalyst can be attributed to the combined beneficial effects of highly dispersed Pt nanoparticles on the CNTs, the existence of oxygen holes in the MoO3 layer structure and the oxidation capability of TiO2.

A rational design of bimetallic PdAu nanoflowers as efficient catalysts for methanol oxidation reaction

Methanol fuel cells have been intensively developed as clean and high-efficiency energy conversion system due to their high efficiency and low emission of pollutants.Here,we developed a simple aqueous synthetic method to prepare bimetallic PdAu nanoflowers catalysts for methanol oxidation reaction(MOR)in alkaline environment.Their composition can be directly tuned by changing the ratio between Pd and Au precursors.Compared with commercial Pd/C catalyst,all of the PdAu nanoflowers catalysts show the enhanced catalytic activity and durability.In particular,the PdAu nanoflowers specific activity reached 0.72 mA/cm^(2),which is 14 times that of commercial Pd/C catalyst.The superior MOR activity could be attributed to the unique porous structure and the shift of the d-band center of Pd.

Two-dimensional PtRu Nanoclusters Carbon Based Electrocatalysts for Methanol Oxidation

A novel method to prepare an electrocatalyst with a new structure and high catalytic performance was reported. Two-dimensional（2 D） PtRu nanoclusters have been successfully deposited on graphene oxide and carbon black supports. Compared with the commercial 3 D E-TEK PtRu samples, the prepared 2 D PtRu composites have larger electrochemically active surface area and display much higher catalytic activity toward methanol oxidation reaction. The preparation method mainly includes the following procedures： oxidation of carbon matrix, Pb^（2＋） adsorption on the surface of carbon support, Pb^（2＋） electrochemical reduction and galvanic displacement of Pb^0 by Pt^（2＋） and Ru^（3＋）. The method developed in this study could be viable for solving the problem of low electrocatalytic activity in direct methanol fuel cell anodes.

Interfacial Electronic Modulation of Dual-Monodispersed Pt–Ni_(3)S_(2) as Efficacious Bi-Functional Electrocatalysts for Concurrent H_(2) Evolution and Methanol Selective Oxidation

Constructing the efficacious and applicable bifunctional electrocatalysts and establishing out the mechanisms of organic electro-oxidation by replacing anodic oxygen evolution reaction(OER) are critical to the development of electrochemicallydriven technologies for efficient hydrogen production and avoid CO_(2) emission. Herein, the hetero-nanocrystals between monodispersed Pt(~ 2 nm) and Ni_(3)S_(2)(~ 9.6 nm) are constructed as active electrocatalysts through interfacial electronic modulation, which exhibit superior bi-functional activities for methanol selective oxidation and H_(2) generation. The experimental and theoretical studies reveal that the asymmetrical charge distribution at Pt–Ni_(3)S_(2) could be modulated by the electronic interaction at the interface of dual-monodispersed heterojunctions, which thus promote the adsorption/desorption of the chemical intermediates at the interface. As a result, the selective conversion from CH_(3)OH to formate is accomplished at very low potentials(1.45 V) to attain 100 m A cm^(-2) with high electronic utilization rate(~ 98%) and without CO_(2) emission. Meanwhile, the Pt–Ni_(3)S_(2) can simultaneously exhibit a broad potential window with outstanding stability and large current densities for hydrogen evolution reaction(HER) at the cathode. Further, the excellent bi-functional performance is also indicated in the coupled methanol oxidation reaction(MOR)//HER reactor by only requiring a cell voltage of 1.60 V to achieve a current density of 50 m A cm^(-2) with good reusability.

Spatial construction of ultrasmall Pt-decorated 3D spinel oxidemodified N-doped graphene nanoarchitectures as high-efficiency methanol oxidation electrocatalysts

Direct methanol fuel cell technology recently becomes the focus of both academic and engineering circles,which stimulates the exploitation and utilization of advanced electrode catalysts with high activity and long lifespan.Herein,we demonstrate a robust bottom-up approach to the spatial construction of three-dimensional(3D) spinel manganese-cobalt oxide-modified N-doped graphene nanoarchitectures decorated with ultrasmall Pt nanoparticles(Pt/MnCo_(2)O_(4)-NG) via a controllable selfassembly process.The incorporation of MnCo_(2)O_(4)nanocrystals provides abundant hydroxyl sources to promote the oxidative removal of CO-like byproducts on Pt sites,while the existence of 3D porous N-doped graphene networks facilitates the transportation of both ions and electrons in the hybrid system,thus giving rise to remarkable synergetic coupling effects during the methanol oxidation process.Consequently,the optimized Pt/MnCo_(2)O_(4)-NG nano architecture expres ses exceptional electrocatalytic properties with a large electrochemically active surface area of 99.5 m^(2)·g^(-1),a high mass activity of1508.3 mA·mg^(-1),strong toxicity resistance and reliable long-term durability,which have obvious competitive advantages over those of conventional Pt/carbon black,Pt/carbon nano tube,Pt/graphene,and Pt/N-doped graphene catalysts with the same Pt usage.

Autocatalytic reduction-assisted synthesis of segmented porous PtTe nanochains for enhancing methanol oxidation reaction

Morphology engineering has been developed as one of the most widely used strategies for improving the performance of electrocatalysts.However,the harsh reaction conditions and cumbersome reaction steps during the nanomaterials synthesis still limit their industrial applications.Herein,one-dimensional(1D)novel-segmented PtTe porous nanochains(PNCs)were successfully synthesized by the template methods assisted by Pt autocatalytic reduction.The PtTe PNCs consist of consecutive mesoporous architectures that provide a large electrochemical surface area(ECSA)and abundant active sites to enhance methanol oxidation reaction(MOR).Furthermore,1D nanostructure as a robust sustaining frame can maintain a high mass/charge transfer rate in a long-term durability test.After 2,000 cyclic voltammetry(CV)cycles,the ECSA value of PtTe PNCs remained as high as 44.47 m^(2)·gPt^(-1),which was much larger than that of commercial Pt/C(3.95 m^(2)·gPt^(-1)).The high catalytic activity and durability of PtTe PNCs are also supported by CO stripping test and density functional theory calculation.This autocatalytic reduction-assisted synthesis provides new insights for designing efficient low-dimensional nanocatalysts.

Degradation of platinum electrocatalysts for methanol oxidation by lead contamination

Platinum exhibits high electrocatalytic activity toward various reactions but might be poisoned by some species. This communication reports a new finding that the electrocatalytic activity of platinum for methanol oxidation will be largely lost in a lead-contaminated environment. This activity loss is demonstrated in an electrochemical cell using a lead counter electrode for measuring the activity of platinum electrode towards methanol oxidation. The recorded methanol oxidation current in this cell is significantly decreased compared with that using a platinum counter electrode. The possible mechanism is related to the adsorption of trace lead ions from the lead counter electrode, as confirmed by comparing the calculated binding energies of platinum and lead ions with oxygen ion. This report is of great importance for reliably designing and efficiently managing direct methanol fuel cells, because trace lead might be present in various components in the fuel cell systems or in air and attention should be paid to its negative effect.

Shape-dependence in seeded-growth of Pd-Cu solid solution from Pd nanostructure towards methanol oxidation electrocatalyst

Ultrathin Pd nanosheets(NSs)have great advantages in catalysis due to their large specific surface area and high percentage of under-coordinated atoms.However,the electrochemical performance still can be improved via composition-controllable growth of their solid solution.Herein,seeded alloying strategy was proposed to synthesize Pd-Cu solid solution from Pd NSs and Pd-Cu nanostructures with tunable molar ratios obtained by changing the amount of Cu precursor.As compared to the pristine Pd NSs,the Pd-Cu solid solution shows significantly enhanced methanol oxidation reaction(MOR)performance over those of Pd NSs and homemade Pd/C as the incorporation of Cu weakens the adsorption of CO intermediate on Pd in the MOR process.The choice of template is pivotal to the growth,as a shape-dependent behavior could be identified in the alloying of Cu with Pd nanosheets enclosed by{111}and{100}facets,Pd nanocubes enclosed by{100}facet,and Pd nano-tetrahedrons enclosed by{111}facet.The Pd-Cu solid solution with tunable composition can only be obtained from Pd NSs and the shape-dependent alloying process is mainly determined by the diffusion barrier and the minimum diffusion depth of the different facets.

Advanced heterostructure of Pd nanosheets@Pt nanoparticles boosts methanol electrooxidation

Heterostructures have emerged as elaborate structures to improve catalytic activity owing to their combined surface and distinct inverse interface.However,fabricating advanced nanocatalysts with facetdependent interface remains an unexploited and promising area.Herein,we render the controlled growth of Pt nanoparticles(NPs)on Pd nanosheets(NSs)by regulating the reduction kinetics of Pt^(2+)with solvents.Specifically,the fast reduction kinetic makes the Pt NPs uniformly deposited on the Pd NSs(U-Pd@Pt HS),while the slow reduction kinetic leads to the preferential growth of Pt NPs on the edge of the Pd NSs(E-Pd@Pt HS).Density functional theory calculations demonstrate that Pd(111)-Pt interface in U-Pd@Pt HS induces the electron-deficient status of Pd substrates,triggering the d-band center downshift and amplifying the Pd-Pt intermetallic interaction.The synergy between the electronic effect and interfacial effect facilitates the removal of poisonous intermediates on U-Pd@Pt HS.By virtue of the Pd NSs@Pt NPs interface,the heterostructure achieves exceptional methanol oxidation reaction activity as well as improved durability.This study innovatively proposes heterostructure engineering with facetdependent interfacial modulation,offering instructive guidelines for the rational design of versatile heterocatalysts.

Two new pseudo-isomeric nickel(Ⅱ)metal-organic frameworks with efficient electrocatalytic activity toward methanol oxidation

Searching for non-noble metal catalysts with high activities and low price is critical to the commercialization of methanol oxidation in the process of fuel cells.Herein,two new pseudo-isomeric Ni metal-organic frameworks(Ni-MOFs)(CTGU-17/CTGU-18)have been prepared with 1,4-naphthalenedi-carboxylate(H_(2)NDC),4,4’-dipyridyl amine(DPA)and Ni(ClO_(4))_(2)under hydrothermal condition.Each phase contains one water molecule,but differs dramatically in its bonding to the framework,resulting in different topological networks with fourfold interpenetrating 4-connected dia net(CTGU-17)and(3,7)-connected net(CTGU-18)and diverse electrocatalytic performance for methanol oxidation reaction(MOR).Remarkably,by combining each MOF with the conductive additive,acetylene black(AB),a composite material,AB&CTGU-18(2:4)was confirmed to have an excellent performance for MOR with a high mass specific peak current of 442.3 mA·mg^(-1).The enhanced electrocatalytic activities and robustness might be attributed to the synergetic effect of acetylene black and the active metal centers of MOFs particles for methanol oxidation.The present work would provide a new insight for the rational design of MOFs-based composites with enhanced methanol oxidation reaction performance.