Characterization of carbon fibrous material from platanus achenes as platinum catalysts support

Carbon materials with developed porosity are usually used as supports for platinum catalysts. Physico-chemical characteristics of the support influence the properties of platinum deposited and its catalytic activity. In our studies, we deposited platinum on carbon fibrous like materials obtained from platanus seeds - achenes. The precursor was chemically activated with different reagents: NaOH, pyrogallol, and H2O2, before the carbonization process. Platinum was deposited on all substrates to study the influence of the substrate properties on the activity of the catalyst. Carbon materials were characterized by nitrogen adsorption/desorption isotherms measurements, X-ray diffraction, and scanning electron microscopy. It was noticed that the adsorption characteristics of carbon support affected the structure of platinum deposits and thus their activity

Electrocatalytic properties of Pt-Bi electrodes towards the electrooxidation of formic acid

Formic acid oxidation was studied on two Pt-Bi catalysts, i.e., Pt2Bi and polycrystalline Pt modified by irreversible adsorbed Bi (Pt/Biirr) in order to establish the difference between the effects of Biirr and Bi in the alloyed state. The results were compared to pure Pt. It was found that both bimetallic catalysts were more active than Pt with the onset potentials shifted to more negative values and the currents at 0.0 V vs. saturated calomel electrode (under steady state conditions) improved by up to two order of magnitude. The origin of the high activity and stability of Pt2Bi was increased selectivity toward formic acid dehydrogenation caused by the ensemble and electronic effects and suppression of Bi leaching from the surface during formic acid oxidation. However, although Pt/Biirr also showed remarkable initial activity compared to pure Pt, dissolution of Bi was not suppressed and poisoning of the electrode surface induced by the dehydration path was observed. Comparison of the initial quasi-steady state and potentiodynamic results obtained for these two Pt-Bi catalysts revealed that the electronic effect, existing only in the alloy, contributed to the earlier start of the reaction, while the maximum current density was determined by the ensemble effect.Oksidacija mravlje kiseline ispitivana je na dva tipa Pt-Bi katalizatora: Pt2Bi elektrodi i na polikristalnoj Pt elektrodi modifikovanoj ireverzibilno adsorbovanim Bi (Pt/Biirr). Aktivnosti su upoređene sa rezultatima dobijenim na čistoj poli- kristalnoj Pt elektrodi. Cilj je bio da se objasni razlika u delovanju ireverzibilno adsorbovanog Bi (Biirr) i Bi u legiranom stanju. Pokazano je da su oba bimetalna katalizatora aktivnija od polikristalne Pt, početak reakcije je pomeren ka negativnijim vrednostima i u poređenju sa čistom Pt pri stacionarnim uslovima dobijene su do dva reda veličine veće gustine struje. Razlog za veliku aktivnost i stabilnost Pt2Bi elektrode u oksidaciji mravlje kiseline je odigravanje reakcije po glavnom reakcionom putu (dehidroganacija mravlje kiseline), što je izazvano efektom trećeg tela i elektronskim efektom, kao i sprečavanje izluživanja Bi iz elektrode. S druge strane, iako Pt/Biirr pokazuje značajnu početnu aktivnost u odnosu na Pt, ova elektroda nije stabilna tokom reakcije oksidacije HCOOH zbog kontinualnog rastvaranja Bi sa površine elektrode, kao i trovanja površine izazvanog tokom reakcije po indirektnom, dehidratacionom putu. Poređenjem rezultata dobijenih na ove dve Pt-Bi elektrode može se objasniti uloga efekta trećeg tela i elektronskog efekta u oksidaciji HCOOH. Naime, elektronski efekat, koji postoji samo kod legure, doprinosi ranijem početku reakcije, dok je maksimalna struja određena efektom trećeg tela. Tokom cikliziranja Pt/Biirr elektrode Bi odlazi sa površine i efekat trećeg tela se gubi tokom vremena. Hronoamperometrijska merenja ukazuju na prednost legure, odnosno neophodnost legiranja Bi sa Pt da bi se dobio koroziono stabilan katalizator

Carbon Supported PtSn versus PtSnO2 Catalysts in Methanol Oxidation

Pt, PtSn and PtSnO2 catalysts supported on high surface area carbon synthesized by microwave assisted polyol procedure were tested for methanol oxidation. Based on TGA, EDX and XRD analysis, PtSn/C is composed of Pt and Pt3Sn phase while the rest of Sn is present in a form of very small tin oxide particles. This paper focuses on structure-activity relationships for CO tolerance and methanol oxidation reactions after addition of Sn to Pt catalysts. Alloying of Sn with Pt improves the rate of CO oxidation despite the fact that the pure Sn does not react with CO and therefore activity for methanol oxidation increases similar to 2 times in comparison to Pt/C catalyst. PtSn/C catalyst shows small advantage in comparison with PtSnO2/C catalyst due to the alloyed Sn and its electronic effect. Long term stability tests also confirmed that PtSn/C catalyst is somewhat better in comparison to PtSnO2/C