Stability and activity of platinum nanoparticles in the oxygen electroreduction reaction: is size or uniformity of primary importance?

Platinum–carbon catalysts are widely used in the manufacturing of proton-exchange membrane fuel cells. Increasing Pt/C activity and stability is an urgent task and the optimization of their structure seems to be one of the possible solutions. In the present paper, Pt/C electrocatalysts containing small (2–2.6 nm) nanoparticles (NPs) of a similar size, uniformly distributed over the surface of a carbon support, were obtained by the original method of liquid-phase synthesis. A comparative study of the structural characteristics, catalytic activity in the oxygen electroreduction reaction (ORR), and durability of the synthesized catalysts, as well as their commercial analogs, was carried out. It was shown that the uniformity of the structural and morphological characteristics of Pt/C catalysts makes it possible to reduce the negative effect of the small size of NPs on their stability. As a result, the obtained catalysts were significantly superior to their commercial analogs regarding ORR activity, but not inferior to them in terms of stability.

Stability and activity of platinum nanoparticles in the oxygen electroreduction reaction: is size or ordering of primary importance?

Platinum-carbon catalysts are widely used in manufacturing proton-exchange membrane fuel cells. Increasing Pt/C activity and stability is an urgent task, optimization of their structure seems to be one of the possible solutions. In the present paper, Pt/C electrocatalysts which contained small (2 - 2.6 nm) nanoparticles of a similar size, uniformly distributed over the surface of a carbon support, were obtained by the original method of liquid-phase synthesis. A comparative study of the structural characteristics, catalytic activity in the oxygen electroreduction reaction and durability of the synthesized catalysts, as well as their commercial analogs has been carried out. It was shown that the ordering of the structural and morphological characteristics of Pt/C catalysts makes it possible to reduce the negative effect of NPs small size on their stability. As a result, the obtained catalysts are significantly superior to their commercial analogs in ORR activity, but not inferior to them in terms of stability.

SYNTHESIS AND ELECTROCHEMICAL CHARACTERISTICS OF Fe (III)-ETIO PORPHYRIN II AND ITS 5,15-BIS(PYRID-3-YL) DERIVATIVE

In this work acetato(3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato)iron(III) [(AcO)FeTMeTEtP] and acetato[5,15-bis(pyrid-3-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato)iron(III) [(OAc)OFe(Py-3)2TMeTEtP] have been synthesized and characterized. Electrochemical properties and electrocatalytic activity of complexes in oxygen electroreduction reaction in 0.1M KOH aqueous solution were studied by the cyclic voltammetry. The comparative analysis of the effect of complex formation, as well as functional substitution in the molecule (the introduction of one or two pyridyl fragments into meso-positions of the macrocycle) on the electrochemical parameters and activity of alkyl-substituted and pyridyl-substituted porphyrins in oxygen electroreduction reaction were carried out. The research of electrochemical behavior of complexes with close structure in experimental conditions has showed that a pyridyl substituent significantly affects the studied properties. The published data and obtained in our work have showed that (AcO)FeTMeTEtP and (AcO)Fe(Py-3)2TMeTEtP are characterized by redox processes involving both the porphyrin macrocycle (L ↔ Lˉ˙, Lˉ˙ ↔ L2ˉ), and metal (Fe3+ ↔ Fe2+, Fe2+ ↔ Fe+). It should be noted that the process of electroreduction of the central metal ion (Fe3+ ↔ Fe2+) proceeds under additional introduction of oxygen into the system for the (AcO)FeTMeTEtP, (Cl)Fe(Py-3)HMeDEtP and (AcO)Fe(Py-3)2TMeTEtP. The results of investigation of the electrocatalytic activity of tetrapyrrole compounds in an aqueous-alkaline medium allows one to make a conclusion about the positive effect of complexation and the introduction of electron-donor substitutes in the porphyrin macrocycle on the electroreduction process of molecular oxygen. The electrocatalytic activity of the studied compounds in the oxygen ionization reaction were increased, according to the decrease in the half-wave potential of O2 [E1/2(O2)] in the series: H2TMeTEtP < (AcO)FeTMeTEtP < (AcO)Fe(Py-3)2TMeTEtP.Forcitation:Berezina N.M., Do Ngoc Minh, Bazanov M.I., Semeikin A.S., Maksimova A.A. Synthesis and electrochemical characteristics of Fe (III) - etio porphyrin ii and its 5,15-bis(pyrid-3-yl) derivative. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 29-34