Based on theoretical simulations, the best design for obtaining AgPt nanostructures (nanoshells with hollow interior) was unraveled that could exhibit methanol tolerance for oxygen reduction reaction (ORR) that occurs during direct methanol fuel cells (DMFCs) operation. A theoretical investigation of Pt@Ag and Ag@Pt core-shell nanoparticles and AgPt nanoshells' interaction with oxygen and methanol revealed that the oxygen interaction is significantly more favorable on AgPt nanoshells' surface, hindering the methanol oxidation reaction (MOR) due to the random arrangement of Ag and Pt atoms. Experimentally, the nanoshells were prepared by a galvanic substitution and immobilized them onto silica, and the material was finely understood by associating electrochemical and physicochemical studies. Cyclic voltammetry showed the reduction and oxidation processes of the catalyst's species; however, XPS precisely showed that significant amounts of oxidized species were present (60.5 % of Ag 0 and 39.5 % of Ag + , and 55.1 % of Pt 0 and 44.9 % of Pt + 2 ), which could affect the performance of the material. Indeed, the catalyst showed an excellent performance to ORR; the system yielded a 4-electron ORR mechanism with just 1.0 wt.% Pt loading, with significant stability after 1000 runs. In addition, Koutecky-Levich and Tafel plots assisted in understanding better the mechanism on the catalyst's surface, suggesting a first-electron transfer for the rate-determining step. Also, the catalyst resistance to the methanol crossover, theoretically simulated and predicted, was tested, showing remarkable tolerance for the alcohol up to a concentration of 2 M. Hence, a cathode catalyst with improved selectivity, low metal loading, high stability, and easy preparation was obtained.
The design and development of efficient and electrocatalytic
sensitive
nickel oxide nanomaterials have attracted attention as they are considered
cost-effective, stable, and abundant electrocatalytic sensors. However,
although innumerable electrocatalysts have been reported, their large-scale
production with the same activity and sensitivity remains challenging.
In this study, we report a simple protocol for the gram-scale synthesis
of uniform NiO nanoflowers (approximately 1.75 g) via a hydrothermal
method for highly selective and sensitive electrocatalytic detection
of hydrazine. The resultant material was characterized by scanning
electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction.
For the production of the modified electrode, NiO nanoflowers were
dispersed in Nafion and drop-cast onto the surface of a glassy carbon
electrode (NiO NF/GCE). By cyclic voltammetry, it was possible to
observe the excellent performance of the modified electrode toward
hydrazine oxidation in alkaline media, providing an oxidation overpotential
of only +0.08 V vs Ag/AgCl. In these conditions, the peak current
response increased linearly with hydrazine concentration ranging from
0.99 to 98.13 μmol L–1. The electrocatalytic
sensor showed a high sensitivity value of 0.10866 μA L μmol–1. The limits of detection and quantification were
0.026 and 0.0898 μmol L–1, respectively. Considering
these results, NiO nanoflowers can be regarded as promising surfaces
for the electrochemical determination of hydrazine, providing interesting
features to explore in the electrocatalytic sensor field.
The Front Cover shows that nanoengineering is a breakthrough way to look at the electrocatalysis field under a different perspective. In their Research Article, M. Aurélio Suller Garcia, T. Silva Rodrigues and co‐workers provided the design of a hollow AgPt‐based electrocatalyst with improved resistance to methanol for Direct Methanol Fuel Cells applications. After immobilization onto SiO2, the nanostructures presented remarkable stability, with a four‐electron oxygen reduction reaction mechanism as the Pt/C commercial catalyst, with 20 times less Pt content. More information can be found in the Research Article by M. Aurélio Suller Garcia, T. Silva Rodrigues and co‐workers.
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