High Electrocatalytic Activity For Oxygen Reduction Reaction Research Articles

Three‐Dimensional Macroporous NiCo2O4 Sheets as a Non‐Noble Catalyst for Efficient Oxygen Reduction Reactions

A facile and low-cost strategy is developed to prepare three-dimensional (3D) macroporous NiCo2 O4 sheets, which can be used as a highly efficient non-noble metal electrocatalyst for the oxygen reduction reaction (ORR) in alkaline conditions. The as-obtained sheets have a thickness of about 150 nm and feature a typical 3D macroporous structure with pore volumes of up to 0.23 cm(3) g(-1) , which could decrease the mass transport resistance and allow easier access of the reactants to the active surface sites. The as-prepared macroporous NiCo2 O4 sheets exhibit high electrocatalytic activity for ORR with a four-electron pathway, good long-term stability and high tolerance against methanol. The unique 3D macroporous structure and intrinsic properties may be responsible for their high performance.

Effect of pyrolysis temperature on cobalt phthalocyanine supported on carbon nanotubes for oxygen reduction reaction

Cobalt phthalocyanine (CoPc)-impregnated functionalized multi-walled carbon nanotubes (CNTs) were used as nonprecious electrocatalysts for oxygen reduction reaction (ORR). The electrocatalysts were thermally treated at temperatures ranging from 450 to 850 °C, and the effect of pyrolysis temperature and their relationship to the electrocatalytic activity for ORR were investigated. Thermo gravimetric analysis, X-ray diffraction, and electron microscopy were used to study the thermal stability, crystal structure, and morphology of these catalysts. Cyclic voltammetry and rotating disk electrode results showed that CoPc/CNTs pyrolyzed at a temperature of 550 °C had the highest electrocatalytic activity for ORR, and the catalytic activity decreased with further increase in pyrolysis temperature. X-ray photoelectron spectroscopy showed decrease in functional groups at a temperature higher than 550 °C, correlating with the decreased catalytic activity. The result suggests that oxygen functional groups introduced by acid oxidation for anchoring the CoPc on CNT plays a major role in determining the electrocatalytic activity.

Polyaniline‐Modified Silver and Binary Silver‐Cobalt Catalysts for Oxygen Reduction Reaction

AbstractNovel dendrite‐like silver particles were electrodeposited on Ti substrates from a supporting electrolyte‐free 30 mmol L−1 Ag(NH3)2+ solution, to synthesize the den‐Ag/Ti electrode. Binary AgxCoy/Ti electrodes with different Ag:Co atomic ratios were further obtained by electrodeposition of Co particles on the den‐Ag/Ti electrode. Polyaniline (PANI) modified den‐Ag/Ti and AgxCoy/Ti electrodes, PANI(n)‐den‐Ag/Ti and PANI(n)‐AgxCoy/Ti, were also obtained by cyclic voltammetry at different numbers of cycles (n) in acidic and alkaline solutions containing aniline, respectively. All these electrodes exhibit high electroactivity for oxygen reduction reaction (ORR) in alkaline solution and their electroactivities follow the order: PANI(15)‐Ag31Co69/Ti>Ag31Co69/Ti>PANI(20)‐den‐Ag/Ti>den‐Ag/Ti. Among them, PANI(15)‐Ag31Co69/Ti displays the highest electrocatalytic activity for ORR with a much positive onset potential of 0 V (vs. Ag/AgCl) and a high ORR current density of 1.2 mA cm−2 at −0.12 V (vs. Ag/AgCl). The electrocatalysts are electrochemically insensitive to methanol and ethanol oxidation, and, as cathode electrocatalysts of direct alcohol fuel cells, can resist poisoning by the possible alcohol crossover from the anode.

Preparation of CoSe nanoparticles by microwave-assisted polyol method: effect of Se/Co ratio, support type and synthesis conditions on oxygen reduction activity

Highly methanol-tolerant CoSe nanoparticles supported on different carbon substrates were synthesized by microwave heating of glycerol solutions of cobalt(II) acetate and sodium selenite at different Se/Co mole ratios in the presence of different concentrations of acetic acid and ammonia. The resulting CoSe catalysts were used for the electrochemical oxygen reduction reaction (ORR) in acidic solution in the presence of methanol. The ORR activity of the catalyst was increased by increasing its Se content up to 50 mol%. The presence of acetic acid or ammonia in the synthesis solution significantly affects the electrocatalytic performance of the CoSe catalyst; highest activity was observed when the catalyst was synthesized at NH3/Co(II) mole ratio of 6. Among the catalysts prepared on different supports including carbon black (Vulcan XC-72R), and nanoporous carbons synthesized from resorcinol-formaldehyde and phloroglucinol-formaldehyde resins, the one supported on the carbon prepared from the last resin exhibited highest electrocatalytic activity for ORR.

Solar exfoliated graphene–carbon nanotube hybrid nano composites as efficient catalyst supports for proton exchange membrane fuel cells

Ultra thin graphene–multi walled carbon nanotube composites prepared by a solar exfoliation technique have been explored as catalyst supports for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). Pt nanoparticles were dispersed on a solar exfoliated graphene-functionalized multi walled carbon nanotube (sG-fMWNT) hybrid nanocomposite, which exhibits higher electrocatalytic activity for ORR than Pt dispersed functionalized solar graphene (f-sG) catalyst support. The single cell PEMFC measurements give maximum power densities of 355 mW cm−2 and 675 mW cm−2 with sG and sG-f MWNT respectively. The improved performance in the power density with the sG-f MWNT fuel cell can be ascribed to the synergistic effect of 1D MWNT and 2D graphene in sG-f MWNT as well as its high electrochemical surface area. The inclusion of MWNT bridges the defects for electron transfer besides increasing the basal spacing between graphene sheets. The good performance and possibility of high throughput production of sG-f MWNT makes this material a promising catalyst support for PEMFC.

Preparation of novel Pt-based nanoparticles by double potential step electrolysis and their electrocatalytic activity for oxygen reduction reaction

We have developed a novel preparation method for Pt-based nanoparticles by means of double potential step electrolysis (DPSE), in which Pt–Ni alloy deposited at the first step and Ni dissolved at the following step. A cycle of the DPSE in a nickel plating bath containing PtCl 6 2− led to the formation of the Pt–Ni nanoparticles with size of about 5.4 ± 1.5 nm, which gradually grew up with repeating the DPSE process, and surface Ni content of the particles by XPS was controllable by changing some parameters of the DPSE. The Pt–Ni nanoparticles deposited by the DPSE were covered with a Pt skin layer, which influence the improvement of both catalytic activity for oxygen reduction reaction (ORR) and corrosion resistance. The Pt–Ni nanoparticles by the DPSE exhibit ca. two times higher electrocatalytic activity for ORR than Pt nanoparticles, and further, of which catalytic activity was maintained high even with more than 1000 cycles of potential cycling test in H 2SO 4 solution, showing good corrosion resistance.

A Composite of Polypyrrole Nanowire: Platinum Modified Electrode for Oxygen Reduction and Methanol Oxidation Reactions

The formation of polypyrrole (PPy) nanowires containing highly dispersed Pt nanoclusters composite was synthesized on glassy carbon electrode (GCE) utilizing cyclic voltammetry (CV) method. Metallic Pt clusters were dispersed in electrically conducting PPy nanowires in order to achieve multielectron-transfer processes in a three-dimensional matrix. The electrocatalytic activities toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) have been investigated by CV and chronoamperometry. The PPy–Pt/GCE provided an ORR peak at about (vs saturated calomel electrode) at . The CV measurements at different scan rates showed that oxygen reduction at the PPy–Pt/GCE was a diffusion-controlled process. For MOR, a high ratio of forward anodic peak current to reverse anodic peak current was observed, indicating an efficient oxidation of methanol to at the PPy–Pt/GCE. Larger surface area and higher electrocatalytic activity for ORR and MOR were found at PPy–Pt nanocomposite in comparison with pure Pt modified electrode, which was attributed to high dispersion of Pt nanoclusters in large surface area of PPy nanowires and synergic effect of the Pt core–PPy shell. The results revealed that the PPy–Pt nanocomposite was an effective electrocatalyst for direct methanol fuel cells.