Research Project: Anot tarafında çok Düşük Stokiyometrik Akışla Çalışan Polimer Elektrolit Membranlı Yakıt Hücresinin Tasarımı, Üretimi ve Çalışma Koşullarına Uygun Membran, Ellektrot ve katalizör Malzemelerin Geliştirilmesi ve Test Edilmesi
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Contributors
Funders
ID
TB.00186
Authors
Kızılel, Rıza
Researcher
Publications
Control of average particle size of carbon aerogel supported platinum nanoparticles by supercritical deposition
(Elsevier, 2017) Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Erkey, Can; Kızılel, Rıza; Bayrakçeken, Ayşe; Zhang, Lichun; Aindow, Mark; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Engineering; Research Center
Supercritical deposition was used to synthesize Pt/carbon aerogel (Pt/CA) electrocatalysts. CAs with average pore diameters of 6, 8 and 19 nm (CA6, CA8 and CA19, respectively) were synthesized and impregnated with Pt(cod)me(2) precursor using supercritical carbon dioxide followed by the thermal conversion of the Pt precursor into its metallic form under N-2 atmosphere at various temperatures between 200 and 1000 degrees C. All of the prepared CAs have high surface areas with very sharp pore size distributions. XRD and TEM results show increased Pt particle size with increasing conversion temperature with a homogenous distribution of nanoparticles on the CA supports. Cyclic voltammetry was used to determine the effect of CA pore properties on electrocatalytic activity. At a conversion temperature of 400 degrees C, the highest and lowest electrochemical surface area values were obtained for Pt/CA19 and Pt/CA6 of (126 and 36 m(2)/g, respectively). Furthermore, Pt/CA19 showed good mass activity whereas Pt/CA6 and Pt/CA8 had lower activity values towards the Oxygen Reduction Reaction (ORR). The mass activity values for Pt/CA19 increased with increasing conversion temperature, except for the sample converted at 1000 degrees C which exhibited the lowest mass activity. The specific activity increased significantly with the conversion temperature up to 600 degrees C which gave a value six times that obtained at 200 degrees C. At 800 degrees C, the specific activity decreased slightly, probably due to a change in the CA structure at this elevated conversion temperature. The Pt/CA19 sample converted at 600 degrees C exhibited the best performance with a mass activity of 0.1 A/mg(pt) and a specific activity of 0.24 mA/cm(2).
Mesoporous carbon aerogel supported PtCu bimetallic nanoparticles via supercritical deposition and their dealloying and electrocatalytic behaviour
(Elsevier, 2018) Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Erkey, Can; Kızılel, Rıza; Yu, Haibo; Aindow, Mark; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Engineering; Research Center
Mesoporous carbon aerogel (CA) supported PtCu bimetallic nanoparticles were prepared via a sequential supercritical deposition (SCD) method using supercritical carbon dioxide (scCO(2)). The effects of deposition order of the metal, annealing temperature and metal composition on the average PtCu particle size, size distribution and dispersion were investigated. Four sets of PtCu/CA samples were prepared with two Pt:Cu molar ratios (1:1 and 1:3) and with two different deposition orders (i.e. either Pt or Cu first). X-ray diffraction and electron microscopy data showed that all of the as-prepared samples formed homogeneously distributed disordered PtCu alloy nanoparticles with narrow particle size distributions on the CA support. Increasing annealing temperature in the range 600-950 degrees C increased the average particle size from 1.8 nm to 4.5 nm and resulted in the elimination of separate Cu nanoparticles on the CA surface. The dealloying of the supported PtCu nanoparticles were carried out by cyclic voltammetry and the activity of the dealloyed nanoparticles (after 300 potential cycles) towards the oxygen reduction reaction (ORR) was investigated using rotating disc electrode (RDE) experiments. During dealloying, peaks associated with bulk dissolution and deposition of Cu and dissolution and re-deposition of Cu from the alloyed PtCu nanoparticles were observed at initial cycles along with peaks associated with creation of new Pt sites. Supported nanoparticles with Pt: Cu molar ratios of 1:1 and 1:3 which were prepared by deposition of Cu first had low activities towards ORR after dealloying. on the contrary, nanoparticles prepared by depositing Pt first exhibited promising electrocatalytic activities after dealloying. Samples with a Pt: Cu molar ratio of 1:3 showed higher activities than those with a molar ratio of 1:1. An enhanced ESA of 137 m(2)/g and dealloying induced enhanced mass activity of 0.123 A/mg(Pt) was obtained using the sample with a Pt: Cu molar ratio of 1:3, which was annealed at 800 degrees C. on the other hand, the same sample annealed at 950 degrees C had the highest specific activity of 0.165 mA/cm(2).
