Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst

Abstract

Ru-doped SnO2 powder, (RuxSn1-x)O2, with a Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass % loading). The (RuxSn1-x)O2 support and the Pt/(RuxSn1-x)O2 catalyst were characterized by X-ray diffraction measurements, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The (RuxSn1-x)O2 was found to be a two-phase material consisting of probably a solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O2 indicated good conductivity of the support and displayed the usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-x)O2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O2 starts at lower positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of the Pt/(RuxSn1-x)O2 catalyst compared to PtRu/C, but also a greater loss in current density over time. A potentiodynamic stability test of the catalysts revealed that deactivation of Pt/(RuxSn1-x)O2 and Pt/C was primarily caused by poisoning of the Pt surface by residues of methanol oxidation, which mostly occurred during the first potential cycle. In the case of PtRu/C, the poisoning of the surface was minor and deactivation was caused by surface area loss of the PtRu.

Sintetizovan je prah SnO2 dopovan rutenijumom, (RuxSn1-x)O2, sa atomskim odnosom Sn:Ru od 9:1, i korišćen kao nosač nanočestica platine. Udeo Pt u dobijenom katalizatoru, Pt/(RuxSn1-x)O2, bio je 30 mas. %. Nosač i katalizator su karakterisani difrakcijom X-zraka, energetski disperzivnom spektroskopijom X-zraka i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da je (RuxSn1-x)O2 dvofazni materijal koji verovatno sadrži čvrst rastvor RuO2 u SnO2 i čist RuO2. Prosečna veličina zrna Pt, određena TEM analizom, iznosi 5,3 nm. Ciklična voltametrija Pt/(RuxSn1-x)O2 ukazala je na dobru provodnost nosača katalizatora i na uobičajene karakteristike Pt. Upoređeni su rezultati elektrohemijske oksidacije COads na Pt/(RuxSn1-x)O2, Pt/C i PtRu/C. Oksidacija COads na Pt/(RuxSn1-x)O2 počinje na negativnijim potencijalima u odnosu na PtRu/C i Pt/C. Potenciodinamičke polarizacione krive i hronoamperometrijske krive za oksidaciju metanola ukazuju na veću početnu aktivnost katalizatora Pt/(RuxSn1-x)O2 u odnosu na PtRu/C, ali i na veće smanjenje gustine struje tokom vremena. Test potenciodinamičke stabilnosti katalizatora je ukazao da je smanjenje aktivnosti Pt/(RuxSn1-x)O2 i Pt/C prvenstveno prouzrokovano trovanjem površine Pt proizvodima nepotpune oksidacije metanola, koje se uglavnom odigrava tokom prvog ciklusa. Kod PtRu/C trovanje površine je minimalno, a smanjenje aktivnosti je prouzrokovano smanjenjem elektrohemijski aktivne površine PtRu.