Protic ionic liquids (ILs) have been recently studied as a potential approach to enhance oxygen reduction reaction (ORR) activity of carbon supported platinum catalysts (Pt/C) for application in polymer electrolyte membrane fuel cells. The high oxygen solubility in the ILs was suggested as one of the main reasons for the accelerated reaction rates. Because the nature of the anion of the IL has been associated with increased oxygen solubility, in this work we survey a number of ionic liquids with various anions to study this effect. While the search for direct correlation between the ORR activities and the oxygen solubilities does not produce any conclusive results, by contrast, the specific activity showed dependence on the availability of oxygenated species free Pt sites. This finding indicates that the inhibition of Pt oxidation and less adsorption of non-reactive species may also play an important role in the enhanced ORR activity. Moreover, the degree of IL coverage on the Pt surface was estimated using (bi)sulfate ions as an indicator. The surface coverage not only affected the ORR activity, but also the Pt dissolution process. This suggests that an optimal balance between activity and stability can be achieved on a partially covered Pt surface. The oxygen reduction reaction (ORR) that occurs on the cathode poses a major hurdle for the efficient utilization of polymer electrolyte fuel cells (PEMFC). Extensive studies have focused on developing novel catalysts to improve the efficiency of this reaction.1,2 The ORR involves multiple steps, among which O 2 + H + + e − ↔ OOH ads and OH ads + H + + e − ↔ H 2 O act as the potential rate determining steps. Simultaneously optimizing the Gibbs free energies for both steps to completely eliminate the overpotential is very challenging, and a ∼350 mV overpotenial is commonly observed, which is independent of the identity of the catalyst.3,4 The large overpotential has been generally attributed to the sluggish kinetics of the ORR and adsorption of oxygenated species (e.g. OH ad ) or other anions. 5 The coverage of the adsorbed oxygenated species (θ OH ad ) is unfavorable for the reaction, and the availability of the free metal surface (as expressed by the (1-θ OH ad ) term) is one of the governing factors for the ORR activity.6,7 As a result, much effort has been dedicated to weakening the bonding of OH to the catalyst surface either by shifting the d-band center of Pt 8,9 or by lateral repulsion from the supports (e.g. metal oxides). 10,11Anion adsorption on Pt also affects the ORR activity, and it is agreed that the occupation of active sites deactivates the sites and reduces the activity.12 In real-world membrane-electrode assembly (MEA), the Nafion membrane and ionomer, constituted by a Teflon-like backbone and an anionic cluster of sulfonic groups, 13 are widely employed as indispensable components. The interface between the Nafion and the metal has received great attention due to the strong irreversible sulfonate anions adsorption on the Pt. 12,[14][15][16] The de...

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Fully convolutional neural networks (FCNs) have shown outstanding performance in many computer vision tasks including salient object detection. However, there still remains two issues needed to be addressed in deep learning based saliency detection. One is the lack of tremendous amount of annotated data to train a network. The other is the lack of robustness for extracting salient objects in images containing complex scenes. In this paper, we present a new architecture−PDNet, a robust prior-model guided depth-enhanced network for RGB-D salient object detection. In contrast to existing works, in which RGB-D values of image pixels are fed directly to a network, the proposed architecture is composed of a master network for processing RGB values, and a sub-network making full use of depth cues and incorporate depth-based features into the master network. To overcome the limited size of the labeled RGB-D dataset for training, we employ a large conventional RGB dataset to pre-train the master network, which proves to contribute largely to the final accuracy. Extensive evaluations over five benchmark datasets demonstrate that our proposed method performs favorably against the state-of-the-art approaches.

We report a conductive TiO 2 nanocoating on carbon nanotubes (CNTs) as a Pt electrocatalyst support that shows a significant enhancement in Pt catalyst activity and durability for the oxygen reduction reaction. By using CNTs as the substrate for TiO 2 nanocoating, the nanoscale morphology of the oxide was retained during heat treatment. After carbon doping of the TiO 2 nanocoating, X-ray photoelectron spectroscopy suggests a shift in the binding energy of Ti 2p, implying a suboxide formation. The X-ray absorption near-edge structure showed the mid-edge and post-edge up to 5010 eV, which are attributed to a 1s / 4p transition and promotion of a photoelectron to higher vacant orbitals of Ti and Ti-O antibonding states. The observed smaller coordination number implies that a suboxide was formed with substitutional carbon. On the other hand, the extended X-ray absorption fine structure showed that carbon also exists in interstitial positions. Electrochemical studies showed that the carbon-doped TiO 2 / CNT support has a much greater electrical conductivity than that of undoped TiO 2 /CNT, demonstrating that carbon doping is an effective way to achieve electrical conductivity in the oxide. Pt supported on the carbon-doped TiO 2 /CNTs (Pt/c-TiO 2 /CNTs) showed a better oxygen reduction activity than a commercial Pt/C catalyst. The catalyst only has a less than 3% loss in activity after electrochemical cycling 5000 times, as compared to an activity loss of about 55% for the Pt/C catalyst. The much better activity and durability of the TiO 2 nanocoating supported Pt was attributed to the oxygen deficient oxide support surfaces and strong metal-support interactions.