Julian Key

Highly dispersed ultrafine Pt nanoparticles on hydrophilic N-doped carbon tubes for improved methanol oxidation

Using hydrophilic nitrogen-doped carbon tubes (N-CTs) as supports, prepared by carbonization of the mixture of lysine and ferric chloride, ultrafine Pt nanoparticles were highly dispersed on the N-CT sidewalls. Electrochemical analyses found that the methanol oxidation activity of the Pt/N-CTs was ∼2.1 times that of a commercial Pt/C catalyst. The improved performance correlated to the high dispersion of ultrafine Pt nanoparticles and the synergistic effect between Pt and the N-CTs.

Ranunculus flower-like Ni(OH)2@Mn2O3 as a high specific capacitance cathode material for alkaline supercapacitors

A novel core–shell Ni(OH)2@Mn2O3 material is presented that bears a particle morphology of striking resemblance to Ranunculus flower heads. A 7.8 wt% of Mn2O3 content in Ni(OH)2@Mn2O3 resulted in an impressively high specific capacitance of 1219.1 F g−1 at 2 A g−1 in alkaline electrolytes.

Room-temperature synthesis with inert bubble templates to produce “clean” PdCoP alloy nanoparticle networks for enhanced hydrazine electro-oxidation

PdCoP alloy nanoparticle networks (ANN) were prepared by simultaneous reduction of PdCl2, CoCl2 and NaH2PO2 with NaBH4 using N2 bubbles as soft-templates at room temperature. The PdCoP ANN porous structure was formed at the inert gas bubble surface, and could be obtained with varying ratios of precursors to produce catalysts with different compositions and catalytic activity. PdCoP ANN produced markedly higher hydrazine oxidation activity than PdCo ANN and PdCoP grain aggregates, and catalytic activity varied with different ratios of Pd, Co and P. We conclude that PdCoP ANN are promising hydrazine oxidation catalysts and that the developed method provides a facile and convenient mean of producing mesoporous catalysts with high-surface area.

A cost effective, highly porous, manganese oxide/carbon supercapacitor material with high rate capability

A porous, cube-shaped, Mn2O3/carbon material of varying sizes was prepared via co-synthesis, in which Mn2O3 homogeneously contacts with carbon. Upon a 100 fold increase in current density, specific capacitance dropped by only 39.0%, and the material showed excellent long-term cycle stability of 89% capacitance retention after 2000 cycles at 2 A g−1.

The Effect of PtRuIr Nanoparticle Crystallinity in Electrocatalytic Methanol Oxidation

Two structural forms of a ternary alloy PtRuIr/C catalyst, one amorphous and one highly crystalline, were synthesized and compared to determine the effect of their respective structures on their activity and stability as anodic catalysts in methanol oxidation. Characterization techniques included TEM, XRD, and EDX. Electrochemical analysis using a glassy carbon disk electrode for cyclic voltammogram and chronoamperometry were tested in a solution of 0.5 mol L−1 CH3OH and 0.5 mol L−1 H2SO4. Amorphous PtRuIr/C catalyst was found to have a larger electrochemical surface area, while the crystalline PtRuIr/C catalyst had both a higher activity in methanol oxidation and increased CO poisoning rate. Crystallinity of the active alloy nanoparticles has a big impact on both methanol oxidation activity and in the CO poisoning rate.

A Co-N-doped carbonized egg white as a high-performance, non-precious metal, electrocatalyst for oxygen reduction

A Co-N-doped carbon material was synthesized by pyrolyzing a mixture of boiled egg white and cobalt nitrate. X-ray diffraction, Raman spectrum, X-ray photoelectron spectroscopy, and scanning electron microscopy were used to investigate the morphology and structure of the synthesized carbon material. Electrochemical analyses show that the Co-N-doped carbonized egg white produced much higher oxygen reduction reaction (ORR) activity and greater stability than the N-doped sample control. In conclusion, the facile method to prepare a high-activity, non-precious metal, ORR catalyst using biomass as the carbon source, offers a step towards the development of low-cost fuel cell catalysts.

Cow dung-derived nitrogen-doped carbon as a cost effective, high activity, oxygen reduction electrocatalyst

N-doped carbon materials are promising metal-free catalysts for the oxygen reduction reaction (ORR) in fuel cells. However, their practical application depends on both significant cost reduction (by using low-cost precursors) and further improvement of their catalytic activity. Herein, we report a low-cost and scalable synthesis procedure to prepare a highly active N-doped carbon ORR catalyst using only cow dung as a source of carbon and nitrogen. The obtained catalyst produced high ORR activity comparable to commercial Pt/C in a 0.1 M KOH solution regarding both ORR onset potential and half-wave potential, and had excellent tolerance to methanol crossover as well as a stable ORR cycling performance. Furthermore, the use of cow dung puts a source of greenhouse gas pollution to good use as an ORR catalyst for clean energy production in fuel cells.

Effect of ni core structure on the electrocatalytic activity of pt-ni/c in methanol oxidation.

Methanol oxidation catalysts comprising an outer Pt-shell with an inner Ni-core supported on carbon, (Pt-Ni/C), were prepared with either crystalline or amorphous Ni core structures. Structural comparisons of the two forms of catalyst were made using transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and methanol oxidation activity compared using CV and chronoamperometry (CA). While both the amorphous Ni core and crystalline Ni core structures were covered by similar Pt shell thickness and structure, the Pt-Ni(amorphous)/C catalyst had higher methanol oxidation activity. The amorphous Ni core thus offers improved Pt usage efficiency in direct methanol fuel cells.

Synthesis of ultrafine amorphous PtP nanoparticles and the effect of PtP crystallinity on methanol oxidation

In this study we report that ultrafine amorphous metallic nanoparticles have a surface structure that is rich in both low-coordination sites and defects that coincides with increased methanol oxidation activity. Ultrafine amorphous platinum-phosphorous nanoparticles supported on Vulcan carbon (PtPa/C) were synthesized, followed by increasing degrees of heat treatment to obtain higher levels of crystallinity in the supported PtP particles. Structural and compositional analysis by various techniques allowed correlation between the structures of various PtP states and their resultant catalytic methanol oxidation activity. Increasing heat treatment temperature increased both the crystallinity and average size of the supported PtP particles. Both factors coincided with decreased methanol oxidation activity and lower carbon monoxide tolerance. The most amorphous PtP nanoparticles had the highest catalytic methanol oxidation activity and strongest tolerance for carbon monoxide.

Toward high practical capacitance of Ni(OH)2 using highly conductive CoB nanochain supports

Ultrathin porous Ni(OH)2 sheets were grown on the surface of nano-chain CoB as cores via a facile two-step solution-based method at ambient conditions. The resultant CoB@Ni(OH)2 of 27.89 wt% Ni(OH)2 loading has a high specific capacitance of 1504.4 F g−1 at 0.5 A g−1, 1293.7 F g−1 at 2 A g−1 and 746.8 F g−1 at 6 A g−1.