Hollow PtNi alloy nanospheres with enhanced activity and methanol tolerance for the oxygen reduction reaction

The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction （ORR） is extremely important for accelerating the commercial viability of direct methanol fuel cells （DMFCs）. In this work, we present an efficient and template-free route for facile synthesis of cyanide （CN^-）-functionalized PtNi hollow nanospheres （PtNi@CN HNSs） with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.

Advances and challenges of methanol-tolerant oxygen reduction reaction electrocatalysts for the direct methanol fuel cell

Methanol cross-over effects from the anode to the cathode are important parameters for reducing catalytic performance in direct methanol fuel cells.A promising candidate catalyst for the cathode in direct methanol fuel cells must have excellent activity toward oxygen reduction reaction and resistance to methanol oxidation reaction.This review focuses on the methanol tolerant noble metal-based electrocatalysts,including platinum and palladium-based alloys,noble metal–carbon based composites,transition metal-based catalysts,carbon-based metal catalysts,and metal-free catalysts.The understanding of the correlation between the activity and the synthesis method,electrolyte environment and stability issues are highlighted.For the transition metal-based catalyst,their activity,stability and methanol tolerance in direct methanol fuel cells and comparisons with those of platinum are particularly discussed.Finally,strategies to enhance the methanol tolerance and hinder the generation of mixed potential in direct methanol fuel cells are also presented.This review provides a perspective for future developments for the scientist in selecting suitable methanol tolerate catalyst for oxygen reduction reaction and designing high-performance practical direct methanol fuel cells.

Methanol Tolerant PWA-Pt/C Catalyst with Excellent Electrocatalytic Activity for Oxygen Reduction in Direct Methanol Fuel Cell

It was reported for the first time that phosphorictungstenic acid （PWA） could promote the oxygen reduction reaction （ORR） and inhibit the methanol oxidation reaction at the cathodic Pt/C catalyst in the direct methanol fuel cell （DMFC）. When the weight ratio of PWA to Pt/C is 1, the composite catalyst increases the reduction current of oxygen by about 38% and decreases the oxidation current of methanol by about 76% compared with that of the Pt/C catalyst.

Methanol Tolerant FeTPP-Pt/C Co-catalysts for the Electroreduction of Oxygen

It was found for the first time that iron tetraphenylporphyrin (FeTPP)-Pt/C showed the good activity for the electroreduction of oxygen and methanol tolerant ability. Their perfor- mances were related to the heat-treatment temperature.

Conversion of PtNi alloy from disordered to ordered for enhanced activity and durability in methanol-tolerant oxygen reduction reactions

The development of cost-effective oxygen reduction reaction （ORR） catalysts with a high methanol tolerance and enhanced durability is highly desirable for direct methanol fuel cells. This work focuses on the conversion of PtNi nanoparticles from a disordered solid solution to an ordered intermetallic compound. Here the effect of this conversion on ORR activity, durability, and methanol tolerance are characterized. X-ray diffraction and transmission electron microscopy results confirm the formation of ordered PtNi intermetallic nanoparticles with high dispersion and a mean particle size of about 7.6 nm. The PtNi intermetallic nanoparticles exhibited enhanced mass and specific activities toward the methanol-tolerant ORR in pure and methanol-containing electrolytes. The specific activity of the ORR at 0.85 V on the PtNi intermetallic nanoparticles is almost 6 times greater than on commercial Pt/C and 3 times greater than on disordered PtNi alloy. Durability tests indicated a minimal loss of ORR activity for PtNi intermetallic nanoparticles after 5,000 potential cycles, whereas the ORR activity decreased by 28% for disordered PtNi alloy. The enhanced methanoltolerant ORR activity and durability may be attributed to the structural and compositional stabilities of the ordered PtNi intermetallic nanoparticles compared relative to the stabilities of the disordered PtNi alloy, strongly suggesting that the PtNi intermetallic nanoparticles may serve as highly active and durable methanol-tolerant ORR electrocatalysts for practical applications.

Multicomponent platinum-free nanoporous Pd-based alloy as an active and methanol-tolerant electrocatalyst for the oxygen reduction reaction

Development of high-performance oxygen reduction reaction （ORR） catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 （np-PdCuTiA1） electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiA1 catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of -3.7 nm. The half-wave potential of np PdCuTiA1 is 0.873 V vs. RHE, more positive than those of PdC （0.756 V vs. RHE） and PtC （0.864 V vs. RHE） catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiA1 in the presence of methanol, and this negative shift is much lower than those of the PdC （50 mV） and PtC （165 mV） catalysts. The enhanced ORR activity of np-PdCuTiA1 has been further rationalized through density functional theory calculations.

Co and N co-modified carbon nanotubes as efficient electrocatalyst for oxygen reduction reaction

It is a big challenge to prepare non-rare metal and high-activity electrocatalysts for oxygen reduction reaction(ORR).In this paper,a cobalt/carbon nanotubes/chitosan composite gel was synthesized and then annealed under nitrogen atmosphere to yield the cobalt and nitrogen co-modified carbon nanotubes(Co-N-CNTs)nanocomposite electrocatalysts.In this strategy,the cobalt component considerably enhanced the ORR activity and improved the degree of graphitic structure to increase the electronic conductivity.The chitosan served as sustainable source for nitrogen doping.The Co-N-CNTs exhibit excellent oxygen reduction reaction(ORR)electrocatalytic activity due to the synergetic effect of Co species and N-doping.The Co-N-CNTs also deliver excellent methanol tolerance and superior long-term durability to that of commercial Pt/C,making it a promising ORR electrocatalyst.

Noble metal-free catalysts for oxygen reduction reaction

Developing noble metal-free catalysts with low cost, high performance and stability for oxygen reduction reaction(ORR) in fuel cells is of great interest to promote sustainable energy devices. In this review, we summarized noble metal-free catalysts for ORR,including non-noble metal-based and heteroatom-doped carbon nanomaterials. Mesoporous structure, homogeneous distribution of nanocrystals and synergistic effect of carbon base and nanocrystals/doped heteroatoms have great effect on the ORR property.The noble metal-free nanomaterials showed comparable catalytic property, better stability and methanol tolerance than commercial platinum(Pt)-based catalysts, showing great potential as substitutes for noble metal-based catalysts. In addition, the challenges and chances of developing noble metal-free ORR catalysts are also discussed.

FeNC Catalysts with High Catalytic Activity and Stability for Oxygen Reduction Reaction

Although Pt-based catalysts have been considered as the most effective electrocatalyst for the cathodic oxygen reduction reaction(ORR) of direct methanol fuel cells(DMFCs), they still suffer from the drawbacks of high cost, poor long-term stability and methanol/CO poisoning effects. Thus, developing low-cost ORR catalysts with high efficiency, durability and antipoisoning ability is of paramount importance. Herein, a series of non-noble metal FeNC materials are prepared through a facile pyrolysis process and used as the electrocatalysts toward ORR in alkaline electrolyte. Results show that the FeNC-800-1h catalyst pyrolyzed at 800 ℃ for 1 h with the mass ratio of Fe(NO)·6HO to melamine being 0.50 exhibits the highest catalytic performance among the as-prepared FeN C catalysts. The half-wave potential of ORR is ca. 0.81 V, which is only 38 m V lower than that on the noble metal Pt/C catalyst. Besides, it also displays higher stability and methanol tolerance than Pt/C. There is almost no change in the current during the chronoamperometric test when methanol is added in the electrolyte whereas significant decrease is found on Pt/C catalyst. This study of FeN C catalysts provides new insights on understanding the ORR mechanism and suggests a promising strategy to develop low-cost and highly efficient non-noble metal electrocatalysts for ORR.