Oxygen electroreduction on carbon-supported Pd nanocubes in acid solutions

The oxygen reduction reaction (ORR) was studied on carbon-supported cubic palladium nanoparticles of different sizes (∼30 nm, ∼10 nm and ∼7 nm). Cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) were used as capping agents to prepare the nanocubes and Pd content in the catalyst samples was 20 and 50 wt%. The surface morphology of the prepared materials was studied by transmission electron microscopy (TEM). The catalyst materials were electrochemically characterised by cyclic voltammetry and CO stripping experiments. The rotating disk electrode (RDE) method was employed for ORR studies in 0.5 M H2SO4 and 0.1 M HClO4 solutions. The ORR results revealed that the specific activity of cubic Pd nanoparticles is higher than that of spherical Pd particles and does not depend on the Pd content in the catalyst, but decreases with decreasing the size of Pd nanocubes. Mass activity of Pd nanocubes increased with decreasing the particle size. The ORR proceeds mainly via 4-electron pathway and the reaction mechanism is similar to that on bulk Pd.This research was financially supported by institutional research funding (IUT20-16) of the Estonian Ministry of Education and Research and by the Estonian Research Council (Grant No. 9323). HE thanks the Archimedes Foundation for scholarship. JMF acknowledges financial support from MINECO (Spain), project CTQ2013-44083-P

Oxygen reduction reaction on carbon-supported palladium nanocubes in alkaline media

Carbon-supported Pd nanocubes with the size of 30, 10 and 7 nm were prepared and their electrocatalytic activity towards the oxygen reduction reaction (ORR) in alkaline solution was studied. For comparison carbon-supported spherical Pd nanoparticles and commercial Pd/C catalyst were used. The catalysts were characterised by transmission electron microscopy, electro-oxidation of carbon monoxide and cyclic voltammetry and the ORR activity was evaluated using the rotating disk electrode method. The ORR on all studied Pd/C catalysts proceeded via four-electron pathway where the rate-limiting step was the transfer of the first electron to O2 molecule. The specific activity of Pd nanocubes was more than two times higher than that of spherical Pd nanoparticles and increased with increasing the particle size.This research was financially supported by institutional research funding (IUT20-16) by the Estonian Ministry of Education and Research and by the Estonian Research Council (Grant No. 9323)

Modified Back Projection Kernel Based Image Super Resolution

In this paper, we propose a new super resolution technique based on iterative interpolation followed by registering them using back projection (BP). Firstly the low resolution image is interpolated and then decimated to four low resolution images. The four low resolution images are interpolated and registered by using BP in order to generate a sharper high resolution image then high resolution image is down sampled and back to the first step. The proposed method has been tested on some bench mark images. The peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) results as well as the visual results shows the superiority of the proposed technique over the conventional and state-of-art image super resolution techniques. In Average, the PSNR is 2.72 dB higher than the bicubic interpolation

Oxygen reduction reaction on Pd nanoparticles supported on novel mesoporous carbon materials

In this work three mesoporous nitrogen-doped carbon support materials were evaluated for oxygen reduction reaction (ORR) in comparison to Vulcan carbon in 0.1 M KOH and 0.5 M H2SO4 solutions. Palladium nanoparticles were synthesised using citrate method and the average particle size of 3.9 ± 0.6 nm was obtained, which was determined from transmission electron microscopy (TEM) images. Unique porosities of these mesoporous engineered catalyst supports (ECS) were evaluated using the BET method and all of the materials displayed similar microporosity, altrough mesopore distribution varied greatly between these materials. Three different loadings of the Pd catalyst were applied to the support materials (varying between 20-40 wt% of Pd) to evaluate the support ability to disperse a large amount of Pd. By comparing the 40 wt% Pd loaded ECS-003604 and Vulcan XC-72R it can be noted that the Vulcan carbon-supported Pd catalyst is more agglomerated. The agglomeration of this catalyst is also noticeable from cyclic voltammetry (CV) studies, where the PdO reduction peak shifts to more positive values as compared to the mesoporous Pd/C counterparts. The ORR kinetics were explored using the rotating disc electrode (RDE) method. In acidic media a Pd catalyst supported on a bimodal mesoporous ECS material showed highest specific activity for oxygen electroreduction, while in alkaline the activity difference is less noticeable between the Pd-based electrocatalyst materials. One of the mesoporous N-doped carbon supported Pd catalyst was also compared to Pd/Vulcan cathode in single-cell alkaline anion exchange membrane fuel cell and improved peak power density was observed.This work was financially supported by the Estonian Research Council (grants PRG723 and PRG4) and by the EU through the European Regional Development Fund (TK141‘Advanced materials and high-technology devices for energy recuperation systems’, TK134 ‘Emerging orders of quantum and nanomaterials’). This work was also supported by the Ministerio de Ciencia e Innovación-FEDER (Spain) Projects PID2019-108136RB-C32 and PID2019-105653GB-100

Enhanced performance of nano-electrocatalysts of Pd and PdCo in neutral and alkaline media

Pd and PdCo nanostructures are synthesized by a soft-template route to be applied as electrocatalysts. Distinctive morphologies are obtained: nanowire-like structures, with mean diameter d = 33 nm (PdNW), forming an entangled network; nanocubes (PdNC) 64 nm in side, and PdCo(NS) nanospheres 60 nm in diameter. Pd:Co feed mol ratios (2:1) and (5:1) are used. Pd and Pd–Co nanostructures both crystallize in an fcc structure. A glassy carbon (GC) electrode is then modified with these colloidal dispersions, and further characterized by electrochemical methods. The modified PdNW/GC, PdNC/GC, and PdCoNS/GC electrodes are applied in the oxygen reduction (ORR) and oxygen evolution (OER) reactions, in a phosphate buffer pH 7 and 0.1 M NaOH solution. Voltammetric measurements are consistent with a diffusion-controlled mechanism, with a four-electron reduction process in each Pd and PdCo nanoelectrode. Resulting values of kinetic parameters indicate that the relative effectiveness of these solutions in ORR may be ordered as PdCo (5:1)NS/GC ≥ PdCo (2:1)NS/GC > PdNC/GC ≥ PdNW/GC > GC. For the OER, Tafel slopes are measured for the nanosized electrodes in both types of supporting electrolytes. Turnover frequencies estimated in alkaline solution for the OER indicate that nanostructured bimetallic PdCoNS/GC electrodes exhibit better activity than Pd/GC ones.Fil: Aguirre, María del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Rivas, Bernabé L. Universidad de Concepción; ChileFil: Fabietti, Luis Maria Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Urreta, Silvia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

Optimal image compression via block-based adaptive colour reduction with minimal contour effect

Current image acquisition devices require tremendous amounts of storage for saving the data returned. This paper overcomes the latter drawback through proposing a colour reduction technique which first subdivides the image into patches, and then makes use of fuzzy c-means and fuzzy-logic-based inference systems, in order to cluster and reduce the number of the unique colours present in each patch, iteratively. The colours available in each patch are quantised, and the emergence of false edges is checked for, by means of the Sobel edge detection algorithm, so as to minimise the contour effect. At the compression stage, a methodology taking advantage of block-based singular value decomposition and wavelet difference reduction is adopted. Considering 35000 sample images from various databases, the proposed method outperforms centre cut, moment-preserving threshold, inter-colour correlation, generic K-means and quantisation by dimensionality reduction