Catalysts For Methanol Oxidation Reaction Research Articles

In-situ Raman unveiled Nb-O-bond-dependency selectivity for methanol electro-oxidation at high current density

Selective methanol oxidation reaction (MOR) to value-added formate can maximize the energy utilization by replacing the high onset-potential and sluggish oxygen evolution reaction. However, to date, only first-row 3d transition metal oxides exhibit the capacity of selective MOR, motivating the design of new kinds of electrocatalysts to further enhance the performance. Here we develop amorphous Nb2O5 as an efficient electrocatalyst, for the first time, for selective MOR to formate, with a low operating potential of 1.47 V vs. RHE to achieve the industry-relevant current densities (>100 mA cm−2) with a formate Faradaic efficiency of ∼100 %. We demonstrate, via operando Raman measurements, that this superior electrochemical MOR capacity originates from the in-situ induced short Nb-O bonds from the amorphous structure. Besides, the interface between amorphous Nb2O5 and nickel foam could also faciltate the MOR. This work may provide insights for designing novel transition metal oxides as efficient catalysts for selective MOR.

Facile synthesis of RuCoOx/N-CNT@PEDOT-SH/Pt for high catalytic performance of the methanol electro-oxidation

The exploration of direct methanol fuel cell (DMFC) catalysts has always been a great challenge. We present a facile method to prepare RuCoOx/N-CNT, composited with PEDOT-SH and supported Pt nanoparticles (Pt NPs) as catalyst for methanol oxidation reaction (MOR). Bimetallic oxide carbon nanotubes (RuCoOx/N-CNT) serve as a carrier and a cocatalyst, especially the introduction of RuOx into CoOx can also generate a large number of oxygen vacancies, which can be used as highly active centers as reactants to provide adsorption (or coordination) sites, facilitating electron transfer between reactants and improving the hydrophilicity of catalysts, thereby promoting redox reaction kinetics. A series of structural characterizations show that alloying and charge redistribution exist in RuCoOx/[email protected]/Pt, and oxygen vacancies can effectively change the electronic structure and improve the exposure of active sites density, thereby enhancing MOR activity. Performance tests such as CV、i-t、stability test show that the electrocatalytic activity of RuCoOx/[email protected]/Pt (2003.3 mA mg-1Pt) is far superior to that of RuCoOx/N-CNT/Pt (1324.8 mA mg-1Pt) and commercial Pt/C (279.6 mA mg-1Pt) catalysts. This strategy can provide a scheme for high-performance, low-cost anode catalyst design in MOR.

Ni/NiO heterojunction anchored on N-doped carbon for the enhanced methanol oxidation

The reasonable construction of an economical catalyst with excellent performance for methanol oxidation reaction (MOR) is one of the key problems to be solved to enhance the efficiency of direct methanol fuel cells (DMFC). Herein, Ni/NiO heterojunction loaded on N-doped carbon substrates (Ni/NiO@NC-T) have been constructed by pyrolyzing metal-organic polymer hydrogel formed by the reaction of Ni2+ and sodium alginate (SA), in which the strong interaction between Ni2+ and SA ensures the nickel content of the as-synthesized samples. The optimum Ni/NiO@NC-300 sample has an excellent activity for MOR with the current density (j) of 225 mA∙cm−2 at 1.6 V under an alkaline medium, which is higher than those of some MOR catalysts previously reported. In addition, the stability and anti-CO poisoning ability of Ni/NiO@NC-300 catalysts are superior to that of Pt/C, which indicates that Ni/NiO@NC-300 has potential application prospect as an MOR catalyst. By density functional theory (DFT) calculation, the superior performance of Ni/NiO@NC-300 is mainly ascribed to the Ni/NiO heterojunction, which can effectively reduce the energy barrier of the rate-determining step (CO* → COOH*) in the MOR process. The work opens a new route for the synthesis of transition metal-based materials as MOR catalysts.

High-performance Mo2C/MWCNT electrocatalyst for MOR: Comparison with MoO2/MWCNT and MoO3/MWCNT

Methanol oxidation reaction (MOR) in the direct methanol fuel cells involves six electron transfer processes, and noble metal based catalysts such as Pt and Pd are still recognized as efficient catalysts for MOR. It is generally accepted that the reaction is mainly related to the d states of precious metal-based catalysts. Transition metal carbides and noble metals exhibit similar d band structure and catalytic properties, among which molybdenum carbide is an effective catalyst. However, molybdenum carbide-based catalysts have not been used in methanol electrooxidation reactions until the present moment, and we tried to use Mo2C/MWCNT for the MOR reaction. Compared with MoO2/MWCNT and MoO3/MWCNT, it is found that Mo2C/MWCNT shows the highest electrocatalytic activity, and the current density of Mo2C/MWCNT is 185 mA cm−2 in 1 M KOH+1 M CH3OH at 0.70 V (vs. Hg/HgO). The current density is about 2.2 times and 1.4 times higher than those of MoO2/MWCNT and MoO3/MWCNT catalysts, respectively, and the electrochemical impedance also decreases markedly. The current density retains 76.19% of the initial catalytic activity after 10 h at the Mo2C/MWCNT electrode, indicating that the catalyst has superior stability for MOR. The reaction pathway of MOR on Mo2C/MWCNT is as follows: CH3OH∗ → CH3O∗→ CH2O∗ → CH2OOH∗ → CH2OO∗ → CHOO∗ → CO2∗. The result not only expands the Mo2C application area, but also provides a new idea for the design of the MOR catalyst.

Enhanced methanol oxidation activity of porous layered Ni/CeO2@CN nanocomposites in alkaline medium

The performance of direct methanol fuel cells (DMFC) partly depends on the development of economical and efficient methanol oxidation catalyst. Here, porous layered Ni/CeO2@CN-T composites were prepared by complexation and pyrolysis two-step methods. The optimal Ni/CeO2@CN-600 for methanol oxidation reaction (MOR) requires only 1.361 V at the current density (j) of 10 mA cm−2, and the j is as high as 229.56 mA cm−2 at 1.642 V, superior to those of the nickel-based catalysts reported. The excellent properties of Ni/CeO2@CN-600 are mainly attributed to the electronic interaction between Ni and CeO2, the uniform dispersion of Ni and CeO2 nanoparticles and its porous layered structure. Meanwhile, it has better stability after 12 h i-t tests. The CO poisoning experiments showed that the anti-CO poisoning ability of Ni/CeO2@CN-600 was obviously stronger than that of Pt/C catalyst in alkaline medium. Finally, the density functional theory (DFT) calculation shows the superior activity of Ni/CeO2 catalysts for MOR is mainly attributed to the higher adsorption energy of Ni/CeO2 for CH3OH and the lower energy barrier.

Production of Pt decorated poly(3,4‐ethylenedioxythiophene)/ERGO/GCEas an efficient catalyst for methanol oxidation reaction

AbstractIn this study, Pt‐decorated poly(3,4‐ethylenedioxythiophene) (PEDOT) electrocatalyst was uniformly coated electrochemically reduced graphene oxide (ERGO) layer on glassy carbon electrode (GCE) has been created using appropriate procedures to facilitate the implementation of the methanol oxidation reaction (MOR). This multi‐layer catalyst was characterized in each production step via Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, field‐emission scanning electron microscopy and energy‐dispersive x‐ray analysis (FESEM‐EDX) morphological analysis beside the electrochemical tests. The favorable structures of both ERGO and PEDOT increase conductivity and electrocatalytic activity toward methanol oxidation, which may create a suitable matrix for Pt loading thanks to the formation of much more active centers for methanol electrooxidation. The results demonstrate that the electrochemical surface area (ECSA) of Pt/PEDOT/ERGO/GCE was 39.1 m2 g−1, and it has a convenient mass activity (MA with 467 mA mg Pt−1) compared to that of commercial Pt/C. According to chronoamperometric analysis, the current density of Pt/PEDOT/ERGO/GCE was stable during the 1200 s of operation. It demonstrated remarkable stability with a final current density of 4.36 mA cm−2.

CuCo2O4 supported graphene quantum dots as a new and promising catalyst for methanol oxidation reaction

Recently, the design of an active electrocatalyst with a unitary structure and high electrocatalytic performance as an efficient and low-cost electrode material has received enormous attention in improving the performance of energy and storage devices. In this study, flower-like CuCo2O4 nanorods are synthesized through the hydrothermal method followed by calcination. Then, CuCo2O4 is hybridized with graphene quantum dots (GQDs) prepared by the pyrolysis method. The structure and morphology of the synthesized electrocatalysts are analyzed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction methods. The electrochemical performance of the prepared materials supported on a glassy carbon electrode is investigated by cyclic voltammetry at different methanol concentrations and various scan rates. Also, chronoamperometry and electrochemical impedance spectroscopy techniques are performed for the evaluation of stability and conductivity. The GQD/CuCo2O4 exhibits a good electrochemical surface area of 19.25 cm2 in 1 M KOH and 4 M methanol. Also, GQD/CuCo2O4 shows a higher current density for methanol oxidation reaction (MOR) than CuCo2O4. The superior electrochemical performance of the GQD/CuCo2O4 can be attributed to the strengthening of the CuCo2O4 nanoparticle structure by a large electrochemically active surface associated with nanoporous morphology in the presence of GQDs. Besides, GQDs enhance the catalyst's performance by increasing electrical conductivity and specific surface area.

Composition-adjustable PtCoCu alloy nanoparticles for promoting methanol oxidation reaction

The accumulation of CO–like intermediates on the catalysts surface severely poisons active sites and, consequently, lowers their catalytic activity toward methanol oxidation reaction (MOR). Previous reports indicated that electrons from Co can transfer to Pt atoms based on the difference in electronegativity, thus facilitating the Pt-based catalysts to split the C—H bonds of methanol molecular and oxidize the intermediates generated during MOR. Comparatively, few works on PtCo-based ternary alloy catalysts for MOR were reported. To this end, here, we report one-step method for the synthesis of PtCoCu alloy catalyst. X–ray photoelectron spectroscopy showed a negative shift of the orbital energy of Pt4f in PtCoCu catalyst, compared to PtCo, PtCu and commercial Pt/XC–72 catalysts. Thus, the prepared PtCoCu not only exhibited a negative shift of 130 mV for CO oxidation in comparison with commercial Pt/XC–72 catalyst but also possessed high electrocatalytic activity for MOR relative to PtCo, PtCu and commercial Pt/XC–72 catalysts. In addition, the adjustment of compositions demonstrated that the proper atomic ratio of Co benefited to boost MOR. Therefore, the current work provides a tactics for the controllable synthesis of ternary alloy catalysts which can also be applied to other electrocatalytic reactions beyond MOR.

Nickel-doped molybdenum diselenide/functionalized multiwalled carbon nanotube as highly efficient non-Pt electrocatalyst toward methanol oxidation reaction

Designing a highly active, cost-effective, poison-resistant, and durable noble-metal-free electrocatalyst is essential for improvement of direct methanol fuel cells performance. In this work, Ni-doped MoSe2 nanosheets were successfully synthesized and integrated with carboxylated multiwalled carbon nanotube (f-MWCNT). The formation of Ni-doped MoSe2/f-MWCNT was confirmed with field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. The prepared nanocomposite was used as an electrochemical catalyst for methanol electro-oxidation. The Ni-doped MoSe2/f-MWCNT electrocatalyst displayed a low onset potential of 0.33 V and methanol oxidation reaction (MOR) activity of 630 mA/cm2 at 0.8 V vs. Ag/AgCl after addition of 1 M methanol in alkaline solution. The proposed electrocatalyst also presented outstanding stability with 90% of its MOR activity retention even after 8000 s. With its facile synthesis, excellent catalytic performance and high stability, Ni-doped MoSe2/f-MWCNT is promising as an inexpensive, CO-resistant and efficient anode catalyst for MOR.

Rapid synthesis of trimetallic alloy PtPdNi nanosponges: structural, morphology and catalytic performance

Pt alloy nanostructures have been explored as promising anode catalysts for methanol oxidation reaction. However, the Pt catalyst have continued to face challenges that are yet to be resolved. Studies have shown that the size and geometric structure can influence a material’s catalytic activity and is related to the synthesis technique. In this study, PtPdNi nanostructures were produced at different synthesis duration. FESEM results show that all the samples exhibited nanosponges structure. The PtPdNi synthesized for 150 s, exhibited higher catalytically active toward methanol oxidation and resistance to carbon monoxide poisoning.

Adjusting the Near-Surface Composition of Pt–Zn Intermetallic Nanoparticles to Enhance Methanol Oxidation Activity and Stability

Platinum-based materials are promising catalysts for methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), but it is challenging to balance activity and stability in actual application. Thus, in our work, the graphitized porous carbon (PC) with a high specific surface area and hierarchical porous structure was successfully prepared as the supported material. Disordered A1-PtZn NPs supported on PC was synthesized via one-step coreduction method at 300 °C and H2 atmosphere. Afterward, an ordered PtZn intermetallic compound (L10-PtZn/PC) was acquired at a higher annealing treatment of 600 °C for 12 h, and L10-PtZn/PC-acid with Pt-skin was also obtained via acid etching. The smaller PtZn nanoparticles (ca. < 5 nm) can be synthesized and distributed on the PC homogeneously. The L10-PtZn/PC-acid catalysts display a high order degree and stronger electronic interaction between Pt and Zn atoms, which is favorable for withstanding CO poisoning in MOR. Thus, the L10-PtZn/PC-acid catalyst has a mass activity of 1130 mA mgPt–1 and a specific activity of 2.23 mA cm–2, which are 3.0 and 2.2 times higher than commercial Pt/C. Additionally, the Pt-skin of L10-PtZn/PC-acid can provide a protection for subsurface Zn and keep the structural stability effectively. Therefore, after 2000 cycles of cyclic voltammetry, the L10-PtZn/PC-acid sample remains 86.62% of the initial peak current density, while commercial Pt/C only retains 47.65%. In situ FTIR studies have demonstrated that the OHads species easily absorbed on the Zn atoms and facilitates a direct pathway without CO in the MOR on the intermetallic PtZn. This work provides a novel strategy to develop an ideal near-surface composition Pt-based nanocatalyst with high activity and stability for direct methanol fuel cells.

One-step synthesis of PtNi anchored on TiO2 nanotube arrays for methanol oxidation

Highly active, stable, economic friendly electrocatalysts play a crucial role for the commercialization of direct methanol fuel cells (DMFCs). One kind of flower-like PtNi bimetallic particle anchored on TiO2 nanotube arrays (PtNi/TNTs/Ti) had been synthesized by one-step electrochemical synthesis as anode catalysts for methanol oxidation reaction (MOR) in this study. The PtNi/TNTs/Ti electrode demonstrated high electrocatalytic activity and durability significantly for MOR. In addition, PtNi100/TNTs/Ti possessed a mass activity of 409.8 mA/mgpt, which was four times greater than that of Pt100/TNTs/Ti electrodes. According to further structure analysis, the improvement in catalytic activity was attributed to lattice compression when Ni atoms entered the Pt lattice accompanied by a 1.02 eV positive shift in Pt 4 f7/2 binding energy, and density functional theory (DFT) calculations indicated that the remarkably enhanced catalytic performance on PtNi through lattice compression arising from the enhanced OH adsorption. It appears promising that this simple method could be adopted to prepare an integrated electrode used as energy and environmental applications.

Trimetallic non-noble NiCoSn alloy as an efficient electrocatalyst towards methanol oxidation and oxygen reduction reactions

The development of a non-noble, highly efficient bifunctional catalyst for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) is the bottleneck in the alkaline direct methanol fuel cells (ADMFC). Ni-based bi/tri metallic alloys are the promising candidates next to the noble metals in the alkaline medium.Herein we present a facile hydrazine-assisted hydrothermal technique to synthesize a trimetallic nickel-cobalt-tin (NiCoSn) alloy as an efficient electrocatalyst for MOR and ORR reactions. The physiochemical analysis confirms the formation of trimetallic alloys with a high surface area. The as-synthesized trimetallic NiCoSn electrocatalyst exhibited superior MOR activity in terms of mass activity (509 mA mg−1 at 1.55 V vs RHE) and stability than the bimetallic alloys in 1.0 M KOH electrolyte. Further, the trimetallic alloy delivered a lower onset and half-wave potential of 0.8 and 0.72 V vs RHE with the favorable four-electron transfer in the oxygen reduction reactions. This work highlights a facile approach for preparing Ni-based trimetallic alloys as a promising candidate for the alkaline direct methanol fuel cells/other catalytic applications.

Nickel decorated on Platinum Confined in MXene as an Electrocatalyst for enhanced Electrooxidation of Methanol

The architecture and evaluation of a potent, cost-efficient anode catalyst for methanol oxidation reactions (MOR) have great significance in Direct Methanol Fuel Cells (DFMC) applications. In this study, Ni decorated Pt confined into the layers of 2D Transition metal carbides–MXenes were synthesized and used as electrocatalyst for MOR. Pt-Ni/MXene electrocatalyst was prepared via wet impregnation method utilizing NaBH4 as a reducing agent. The Pt-Ni/MXene nanocomposite formation was verified through XRD, SEM, EDX, TEM, and BET, XPS analysis. Cyclic voltammetry, Chronoamperometric, and electrochemical impedance spectroscopy analysis revealed the Electrochemical performance of Pt-Ni/MXene for electrooxidation of methanol. The synergistic effect of Ni decorated Pt and MXene nanoparticles offered improved durability (84.7 % of retention after 400 cycles) for the Pt-Ni/MXene electrocatalyst for MOR. The electrochemical performance of Pt-Ni/MXene was compared with Pt/MXene, a conventional Pt/C catalyst, and found to exhibit an eight-fold enhancement in catalytic efficiency for MOR in an acidic medium.

Synthesis of intermetallic FePtPd nanoparticles and their enhanced catalysis for electro-oxidation of methanol

Searching for efficient and CO-tolerant catalysts for electro-oxidation of methanol is desirable for the development of direct-methanol fuel cells. Here, we present a novel and facile procedure for the synthesis of intermetallic face-centered tetragonal (fct)-Fe50PtxPd50-x Nanoparticles (NPs) with Fe and Pt/Pd atoms forming alternative layers, which are highly active and stable in catalyzing methanol oxidation reaction (MOR) in 0.1 M HClO4 and 0.2 M methanol aqueous solution. The carbon-supported fct-Fe48Pt35Pd17 NPs show the highest peak current density of 626 A g−1Pt at 909 mV (vs RHE) over fcc-Fe48Pt35Pd17 (428 Ag−1Pt at 930 mV) and the commercial Pt (218 Ag−1Pt at 952 mV). The superior performance observed on the fct-Fe48Pt35Pd17 NPs is attributed to the stabilization of Pd by the intermetallic fct-structure, which improves the Pt CO-tolerance and catalytic activity. The activity of fct-FePtPd depends further on the Pt/Pd ratios. An increase in Pd content improves CO tolerance but reduces the number of active Pt sites on NPs surface, and the optimized Pt/Pd ratio should be around 1.0. Our work demonstrates a new approach to the rational design and synthesis of highly active NP catalysts for MOR.

High-performance methanol electrolysis towards energy-saving hydrogen production: Using Cu2O-Cu decorated Ni2P nanoarray as bifunctional monolithic catalyst

Electrocatalytic methanol oxidation reaction (MOR) is a promising alternative approach to oxygen evolution reaction for efficient hydrogen production. However, developing highly efficient and cost-effective MOR catalysts, coupled with the cathodic hydrogen evolution reaction, is still a challenge. Herein, we used a Ni2P nanosheet array with Cu2O-Cu dendrites on nickel foam (Cu2O-Cu@Ni2P/NF) as an efficient and stable electrocatalyst for MOR, which attained a low potential of 1.41 V at 100 mA cm−2 and a small Tafel slope of 44.99 mV dec–1 with excellent stability for at least 24 h in 1.0 M KOH solution with 1.0 M methanol. In situ Raman spectroscopy reveals that Cu2O-Cu promotes the generation of the β-NiOOH active phase, and converts to Cu(II)O under the electrolysis conditions. Furthermore, the methanol electrolysis cell utilizing Cu2O-Cu@Ni2P/NF as both the cathode and anode delivered a current density of 10 mA cm−2 at a low cell voltage of 1.40 V, and the cell voltage decreased by 210 mV at a current density of 100 mA cm−2 compared to water electrolysis. This work provides a new strategy to design the promising Ni-based phosphide as a bifunctional electrocatalyst in methanol electrolysis, enabling energy-saving H2 production.

A new insight into the promoting effects of transition metal phosphides in methanol electrooxidation

The construction of highly active catalysts for methanol oxidation reaction (MOR) is central to direct methanol fuel cells. Tremendous progress has been made in transition metal phosphides (TMPs) based catalysts. However, TMPs would be partially damaged and transformed into new substances (e.g., Pt-M-P composite, where M represents a second transition metal) during Pt deposition process. This would pose a large obstacle to the cognition of the real promoting effects of TMPs in MOR. Herein, Co2P co-catalysts (Pt-P/Co2P@NPC, where NPC stands for N and P co-doped carbon) and Pt-Co-P composite catalysts (Pt-Co-P/NPC) were controllably synthesized. Electrocatalysis tests show that the Pt-Co-P/NPC exhibits superior MOR activity as high as 1016 mA/mgPt, significantly exceeding that of Pt-P/Co2P@NPC (345 mA/mgPt). This result indicates that the promoting effect is ascribed primarily to the resultant Pt-Co-P composite, in sharply contrast to previous viewpoint that Co2P itself improves the activity. Further mechanistic studies reveal that Pt-Co-P/NPC exhibits much stronger electron interaction and thus manifesting a remarkably weaker CO absorption than Pt-P/Co2P@NPC and Pt/C. Moreover, Pt-Co-P is also more capable of producing oxygen-containing adsorbate and thus accelerating the removal of surface-bonded CO*, ultimately boosting the MOR performance.

(Digital Presentation) Electrocatalytic Oxidation of Methanol over Silver Based Electrocatalysts Synthesized By Solution Combustion Technique

Herein, we report the electrocatalytic properties of Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) catalysts produced using solution combustion synthesis (SCS) method for methanol oxidation reaction (MOR). The morphological properties of the synthesized catalysts were studied using SEM, EDX, TEM, XRD and XPS techniques. The characterization results indicated that out of all catalysts, AgCu/C had the most porous surface, small and well distributed particles with high surface area making it a good choice for electrocatalytic experiments. The XPS results showed a shift in peak in the AgCu/C sample due to the charge transfer between Ag and Cu indicating a strong interaction between Ag and Cu. The electrochemical properties of the catalysts were studied at 1 M methanol concentration and 1 M KOH (electrolyte) concentration by performing Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) experiments. It was observed that AgCu/C exhibited a greater electrocatalytic activity and was therefore, found to be a more viable catalyst for MOR. Following this, further concentration studies were conducted on AgCu/C for methanol concentrations of 0.5M, 1M, 1.5M, 2.5M to evaluate the rate dependency of the catalyst on MeOH concentration. The CV and LSV curves depicted a linear increase in current density proportional to the increase in methanol concentration, indicating power-law dependency. The catalyst also displayed long-term stability when chronoamperometry test was performed for 20 hours.

CO2 and Formate Pathway of Methanol Electrooxidation at Rhodium Electrodes in Alkaline Media: An In Situ Electrochemical Attenuated Total Refection Surface-Enhanced Infrared Absorption Spectroscopy and Infrared Reflection Absorption Spectroscopy Investigation.

Rh catalysts exhibit unexpected high activity for the methanol oxidation reaction (MOR) in alkaline conditions, making them potential anodic catalysts for direct methanol fuel cells (DMFCs). Nevertheless, the MOR mechanism on Rh electrodes has not been clarified thus far, which impedes the development of high-efficiency Rh-based MOR catalysts. To investigate it, a combination of in situ electrochemical techniques called attenuated total refection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and infrared reflection absorption spectroscopy (IRAS) is used. Cyclic voltammograms of MOR at Rh electrodes show considerable activity in alkaline media rather than acidic media, although the real-time ATR-SEIRA spectral results demonstrate that methanol can rarely self-decompose on Rh at open-circuit conditions. Meanwhile, in combination of ATR-SEIRAS and IRAS results, CO2 and formate are thought to be MOR products, suggesting a dual-pathway mechanism ("CO2 pathway" and "formate pathway"). Specifically, COad species, which are the major intermediates in the CO2 pathway, can produce at lower potentials and be oxidized into CO2 at a potential of 0.5-0.75 V. Concurrently, the formate can be produced from 0.5 V and diffuse into the bulk electrolyte to become one of the MOR products, while the further electrochemical conversion of formate to CO2 is essentially negligible. More directly, the apparent selectivity (r) of the CO2 pathway is estimated to reach ca. 0.63 at 0.9 V, confirming the potential-dependent selectivity of MOR at Rh surfaces. This study might provide fresh insights into the design and fabrication of effective Rh-based catalysts for MOR.

Revealing the Effect of Surface Composition on Multiwalled Carbon Nanotubes Supported Pt-Fe Alloy Electrocatalysts for Methanol Oxidation Performance.

The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1 Fe3 @NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt ) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt ). Furthermore, the CO oxidation initial potential of Pt1 Fe3 @NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1 Fe3 @NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field.