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.

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.

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.

Stable NiPt-Mo_(2)C active site pairs enable boosted water splitting and direct methanol fuel cell

Sluggish kinetics of methanol oxidation reaction(MOR)and alkaline hydrogen evolution reaction(HER)even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell(DMFC)and water electrolysis technologies.Since both of MOR and alkaline HER are related to water dissociation reaction(WDR),it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on Pt.Mo_(2)C and Ni species are therefore employed to engineer NiPt-Mo_(2)C active site pairs,which can be encapsulated in carbon cages,via an in-situ self-confinement strategy.Mass activity of Pt in NiPt-Mo_(2)C@C toward HER is boosted to11.3 A mg_(pt)^(-1),33 times higher than that of Pt/C.Similarly,MOR catalytic activity of Pt in NiPt-Mo_(2)C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by 9-fold.By considering the great stability,NiPt-Mo_(2)C@C exhibits great practical application potential in DMFCs and water electrolysers.

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.

Greatly Enhanced Methanol Oxidation Reaction of CoPt Truncated Octahedral Nanoparticles by External Magnetic Fields

Tunable behavior in electrocatalysis by external multifields,such as magnetic field,thermal field,and electric field,is the most promising strategy to expand the theory,design,and synthesis of state-of-the-art catalysts and the cell in the near future.Here,a systematic investigation for the effect of external magnetic field and thermal field on methanol oxidation reactions(MOR)in magnetic nanoparticles is reported.For Co_(42)Pt_(58)truncated octahedral nanoparticles(TONPs),the catalytic performance in MOR is greatly increased to the maximum of 14.1%by applying a magnetic field up to 3000 Oe,and it shows a monotonical increase with increasing working temperature.The magnetic enhanced effect is closely related to the Co content of Co_(x)Pt_(100-x)TONPs.Furthermore,the enhancement effect under a magnetic field is more obvious for Co_(42)Pt_(58)TONPs annealed at 650℃.First-principle calculation points out that the magnetic fields can facilitate the dehydrogenation of both methanol and water by suppression of entropy of the electron spin and lowering of the activation barrier,where OH_(ad)intermediates on Co sites play a more important role.The application of magnetic fields together with thermal fields in MOR provides a new prospect to manipulate the performance of direct methanol fuel cells,which will accelerate their potential applications.

Tungsten carbide-reduced graphene oxide intercalation compound as co-catalyst for methanol oxidation

Highly dispersed tungsten carbide（WC） nanoparticles（NPs） sandwiched between few-layer reduced graphene oxide（RGO） have been successfully synthesized by using thiourea as an anchoring and inducing reagent.The metatungstate ion,[H2W（12）O（40）]^6-,is assembled on thiourea-modified graphene oxide（GO） by an impregnation method.The WC NPs,with a mean diameter of 1.5 nm,are obtained through a process whereby ammonium metatungstate first turns to WS2,which then forms an intercalation compound with RGO before growing,in situ,to WC NPs.The Pt/WC-RGO electrocatalysts are fabricated by a microwave-assisted method.The intimate contacts between Pt,WC,and RGO are confirmed by X-ray diffraction,scanning electron microscope,transmission electron microscope,and Raman spectroscopy.For methanol oxidation,the Pt/WC-RGO electrocatalyst exhibited an electrochemical surface area value of 246.1 m^2/g Pt and a peak current density of1364.7 mA/mg Pt,which are,respectively,3.66 and 4.77 times greater than those of commercial Pt/C electrocatalyst（67.2 m^2/g Pt,286.0 mA/mg Pt）.The excellent CO-poisoning resistance and long-term stability of the electrocatalyst are also evidenced by CO stripping,chronoamperometry,and accelerated durability testing.Because Pt/WC-RGO has higher catalytic activity compared with that of commercial Pt/C,as a result of its intercalated structure and synergistic effect,less Pt will be required for the same performance,which in turn will reduce the cost of the fuel cell.The present method is facile,efficient,and scalable for mass production of the nanomaterials.

Fabricating Core-Shell WC@C/Pt Structures and its Enhanced Performance for Methanol Electrooxidation

The spray-dried spheres within a W/Pt multi-separation can be used to prepare discrete core-shell WC@C/Pt catalysts through a typical carburization production mechanism at 800 ℃. In contrast with previous studies of the WC/Pt synthesis, the reaction observed here proceeds through an indirect annealing thereby resulting in core-shell structure, and mechanism at 600℃ wherein species diffuse, Pt nanoparticles were successfully dispersed in size/shape and randomly scattered across the in situ produced C spheres. Through direct carburization or at higher initial hydrochloroplatiuic acid concentrations, however, complete reaction with core-shell spheres was not observed. Indirect carburization reduces the strain felt by the bonds featuring the larger WC WC and Pt nanoparticles to be reserved, stability toward methanol oxidation. particles and allows the motion of carbon around influencing the eleetrocatalytic performance and

Study on Methanol Oxidation at Pt and PtRu Electrodes by Combining in situ Infrared Spectroscopy and Differential Electrochemical Mass Spectrometry

Methanol oxidation reaction （MOR） at Pt and Pt electrode surface deposited with various amounts of Ru （denoted as PtxRuy, nominal coverage y is 0.17, 0.27, and 0.44 ML） in 0.1 mol/L HClO4＋0.5 mol/L MeOH has been studied under potentiostatic conditions by in situ FTIR spectroscopy in attenuated-total-reflection con guration and di erential electro-chemical mass spectrometry under controlled flow conditions. Results reveal that （i） CO is the only methanol-related adsorbate observed by IR spectroscopy at all the Pt and PtRu electrodes examined at potentials from 0.3 V to 0.6 V （vs. RHE）; （ii） at Pt0.56Ru0.44, two IR bands, one from CO adsorbed at Ru islands and the other from COL at Pt substrate are detected, while at other electrodes, only a single band for COL adsorbed at Pt is observed; （iii） MOR activity decreases in the order of Pt0.73Ru0.27〉Pt0.56Ru0.44〉Pt0.83Ru0.17〉Pt; （iv） at 0.5 V, MOR at Pt0.73Ru0.27 reaches a current e ciency of 50% for CO2 production, the turn-over frequency from CH3OH to CO2 is ca. 0.1 molecule/（site sec）. Suggestions for further improving of PtRu catalysts for MOR are provided.

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.

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.

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.

Hierarchically skeletal multi-layered Pt-Ni nanocrystals for highly efficient oxygen reduction and methanol oxidation reactions

Pt based materials are the most efficient electrocatalysts for the oxygen reduction reaction(ORR)and methanol oxidation reaction(MOR)in fuel cells.Maximizing the utilization of Pt based materials by modulating their morphologies to expose more active sites is a fundamental objective for the practical application of fuel cells.Herein,we report a new class of hierarchically skeletal Pt-Ni nanocrystals(HSNs)with a multi-layered structure,prepared by an inorganic acid-induced solvothermal method.The addition of H_(2)SO_(4)to the synthetic protocol provides a critical trigger for the successful growth of Pt-Ni nanocrystals with the desired structure.The Pt-Ni HSNs synthesized by this method exhibit enhanced mass activity of 1.25 A mgpt−1 at 0.9 V(versus the reversible hydrogen electrode)towards ORR in 0.1-M HClO_(4),which is superior to that of Pt-Ni multi-branched nanocrystals obtained by the same method in the absence of inorganic acid;it is additionally 8.9-fold higher than that of the commercial Pt/C catalyst.Meanwhile,it displays enhanced stability,with only 21.6%mass activity loss after 10,000 cycles(0.6–1.0 V)for ORR.Furthermore,the Pt-Ni HSNs show enhanced activity and anti-toxic ability in CO for MOR.The superb activity of the Pt-Ni HSNs for ORR and MOR is fully attributed to an extensively exposed electrochemical surface area and high intrinsic activity,induced by strain effects,provided by the unique hierarchically skeletal alloy structure.The novel open and hierarchical structure of Pt-Ni alloy provides a promising approach for significant improvements of the activity of Pt based alloy electrocatalysts.

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.

Electrochemically exfoliated graphene as high-performance catalyst support to promote electrocatalytic oxidation of methanol on Pt catalysts

Electrochemically exfoliated graphene(EEG)is a kind of high-quality graphene with few oxygen-containing functional groups and defects on the surface,and thereby is more suitable as catalyst support than other carbon materials such as extensively used reduced graphene oxide(rGO).However,it is difficult to grow functional materials on EEG due to its inert surface.In this work,ultra-small Pt nanocrystals(~2.6 nm)are successfully formed on EEG and show better electrocatalytic activity towards methanol oxidation than Pt catalysts on r GO.The outstanding catalytic properties of Pt catalysts on EEG can be attributed to the fast electron transfer through EEG and high quality of Pt catalysts such as small grain size,high dispersibility and low oxidation ratio.In addition,SnO2 nanocrystals are controllably generated around Pt catalysts on EEG to raise the poison tolerance of Pt catalysts through using glycine as a linker.Owing to its outstanding properties such as high electrical conductivity and mechanical strength,EEG is expected to be widely used as a novel support for catalysts.

Facile synthesis of 3D nanoporous Pd/Co_2O_3 composites with enhanced catalytic performance for methanol oxidation

To simultaneously reduce noble metal Pd usage and enhance electrocatalytic performance for methanol oxidation,Pd/Co2O3 composites with ultrafine three-dimensional(3D)nanoporous structures were designed and synthesized by simple one-step dealloying of a melt-spun Al-Pd-Co alloy with an alkaline solution.Their electrocatalytic activity in alkaline media was determined by a Versa-STAT MC workstation.The results indicate that the typical sizes of the ligaments and pores of the composites were approximately 8-9 nm.The Co2O3 was uniformly distributed on the Pd ligament surface.Among the as-prepared samples,the nanoporous Pd/Co2O3 composite generated from dealloying of the Al84.5Pd15Co0.5 alloy had the best electrocatalytic activity,and its activity was enhanced by approximately 230%compared with the nanoporous Pd from dealloying of Al85Pd15.The improvement of the electrocatalytic performance was mainly attributed to the electronic modification effect between Pd and Co as well as the bifunctional mechanism between Pd and Co2O3.

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.

Surface elemental distribution effect of Pt-Pb hexagonal nanoplates for electrocatalytic methanol oxidation reaction

Bimetallic Pt-based catalysts have been extensively investigated to enhance the performance of direct methanol fuel cells(DMFCs) because CO, a by-product, reduces the activity of the pure Pt catalysts. Herein, we synthesized Pt-Pb hexagonal nanoplates as a model catalyst for the methanol oxidation reaction(MOR) and further controlled the Pt and Pb distributions on the surface of the nanoplates through acetic acid(HAc) treatment. As a result, we obtained Pt-Pb nanoplates and HAc-treated Pt-Pb nanoplates with homogeneous and heterogeneous distributions of the Pt-Pb alloy surfaces, respectively. We showed that the MOR activity and stability of the Pt-Pb nanoplates improved compared to those of the HAc-treated Pt-Pb nanoplates, mainly due to the enhanced CO tolerance and the modified electronic structure of Pt under the influence of the oxophilic Pb.

Composition-controlled synthesis of platinum and palladium nanoalloys as highly active electrocatalysts for methanol oxidation

Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance.