The effect on the electrocatalytic activity of the chemical interaction of selenium with palladium centers: oxygen reduction and methanol oxidation reactions in alkaline medium.

The chemical reactivity of two different selenium precursors (SeO2and Se) with nanoparticulated palladium was studied in a simple aqueous phase synthesis to generate palladium selenides (PdxSey). As confirmed by XRD, XPS, TEM and energy dispersive spectroscopy analyses, the products generated showed different degrees of selenization according to the nature of the chemical precursor. Such degree of selenization was more important with elemental selenium, in contrast to SeO2. Surface electrochemistry and CO stripping in alkaline medium, clearly revealed the different interactions and stability of PdxSeyachieved with the Pd/C precursor depending on the selenium source. The electrocatalysis of the oxygen reduction reaction was also influenced by the Se source, first in the different degree of reactivity, and second in the selectivity of the reduction product between H2O and H2O2, as well as the tolerance to the methanol oxidation reaction.

Cobalt-Based Multicomponent Oxygen Reduction Reaction Electrocatalysts Generated by Melamine Thermal Pyrolysis with High Performance in an Alkaline Hydrogen/Oxygen Microfuel Cell.

A series of cobalt-based multicomponent electrocatalysts (Co-Cat-T) for the oxygen reduction reaction (ORR) were synthesized by thermal pyrolysis of activated carbon-supported cobalt and melamine mixture from 500 to 800 °C. Their corresponding electrocatalytic performance was systematically investigated toward ORR in an alkaline electrolyte. The electrocatalyst chemical composition and structure evolution (e.g., microstrain, crystallite size, and cell volume) were confirmed by X-ray diffraction Rietveld analyses. The material generated at 550 °C (Co-Cat-T550) showed the largest cell volume of the C3N4 phase with a crystallite size of 4.1 ± 0.1 nm. Independent of the heat-treatment temperature, the cobalt atom was coordinated to nitrogen moieties. The following findings: cobalt inserted in the carbon nitride framework (Co-g-C3N4), abundant Co-Nx and pyridinic-N species, unique encapsulated cross-tubular structure, and disordered carbon domains performed better in the ORR with Co-Cat-T550 among the obtained electrocatalysts. In addition, Co-Cat-T550 showed performance comparable to Pt/C in an alkaline hydrogen/oxygen microfuel cell platform.

Molybdenum Doping Augments Platinum-Copper Oxygen Reduction Electrocatalyst.

Improving the efficiency of Pt-based oxygen reduction reaction (ORR) catalysts while also reducing costs remains an important challenge in energy research. To this end, we synthesized highly stable and active carbon-supported Mo-doped PtCu (Mo-PtCu/C) nanoparticles (NPs) from readily available precursors in a facile one-pot reaction. Mo-PtCu/C displays two-to-fourfold-higher ORR half-cell kinetics than reference PtCu/C and Pt/C materials, a trend that was confirmed in proof-of-concept experiments by using a H2 /O2 microlaminar fuel cell. This Mo-induced activity increase mirrors observations for Mo-PtNi/C NPs and possibly suggests an emerging trend. Electrochemical-accelerated stability tests revealed that dealloying was greatly reduced in Mo-PtCu/C in contrast to the binary alloys PtCu/C and PtMo/C. Supporting DFT studies suggested that the exceptional stability of Mo-PtCu could be attributed to oxidative resistance of the Mo-doped atoms. Furthermore, our calculations revealed that oxygen could induce segregation of Mo to the catalytic surface, at which it effected beneficial changes to the surface oxygen adsorption energetics in the context of the Sabatier principle.