Jane Hvolbæk Nielsen

Mass-selected nanoparticles of PtxY as model catalysts for oxygen electroreduction

Low-temperature fuel cells are limited by the oxygen reduction reaction, and their widespread implementation in automotive vehicles is hindered by the cost of platinum, currently the best-known catalyst for reducing oxygen in terms of both activity and stability. One solution is to decrease the amount of platinum required, for example by alloying, but without detrimentally affecting its properties. The alloy PtxY is known to be active and stable, but its synthesis in nanoparticulate form has proved challenging, which limits its further study. Herein we demonstrate the synthesis, characterization and catalyst testing of model PtxY nanoparticles prepared through the gas-aggregation technique. The catalysts reported here are highly active, with a mass activity of up to 3.05 A mgPt(-1) at 0.9 V versus a reversible hydrogen electrode. Using a variety of characterization techniques, we show that the enhanced activity of PtxY over elemental platinum results exclusively from a compressive strain exerted on the platinum surface atoms by the alloy core.

An Open-Source Data Storage and Visualization Back End for Experimental Data

In this article, a flexible free and open-source software system for data logging and presentation will be described. The system is highly modular and adaptable and can be used in any laboratory in which continuous and/or ad hoc measurements require centralized storage. A presentation component for the data back end has furthermore been written that enables live visualization of data on any device capable of displaying Web pages. The system consists of three parts: data-logging clients, a data server, and a data presentation Web site. The logging of data from independent clients leads to high resilience to equipment failure, whereas the central storage of data dramatically eases backup and data exchange. The visualization front end allows direct monitoring of acquired data to see live progress of long-duration experiments. This enables the user to alter experimental conditions based on these data and to interfere with the experiment if needed. The data stored consist both of specific measurements and of continuously logged system parameters. The latter is crucial to a variety of automation and surveillance features, and three cases of such features are described: monitoring system health, getting status of long-duration experiments, and implementation of instant alarms in the event of failure.

Novel micro-reactor flow cell for investigation of model catalysts using in situ grazing-incidence X-ray scattering

The design and performance of a novel micro-reactor in situ flow cell permitting investigation of model catalysts with grazing-incidence small- and wide-angle X-ray scattering is presented.

Morphology of Ruthenium Particles for Methanation under Reactive Conditions

The potential of hydrogen as a future energy carrier is only fully unleashed if fuel processors generating hydrogen of a suitable purity can be engineered. Selective methanation of CO can be used as a first step for cleaning up feed gas for e.g. proton exchange membrane (PEM) fuel cells [1] where CO poison the platinum electrodes and for removing oxygen containing compounds in hydrogen used in ammonia plants [2].

Local composition of alloy catalysts for oxygen reduction by STEM-EDS

Fuel cell technology is a potentially clean alternative to traditional power sources, in particular for the automotive industry [1]. The widespread usability is limited by the high cost of the Pt cathode catalyst [2]. Numerous studies therefore focus on finding cheaper alternative catalysts with higher efficiency for the oxygen reduction reaction (ORR) [3]. Bimetallic catalysts are known for their enhanced ORR activity [3,4]. Pt3Y has been identified based on density functional theory calculations as being both active and stable for ORR. Recent experimental results have shown that PtxY in nanoparticulate form exhibit an unprecedented ORR activity of 3.05 A/mg at 0.9 V with respect to a reversible hydrogen electrode [5,6]. Following the same scheme but focusing on the electrochemical oxygen reduction for the production of hydrogen peroxide, Pd-Hg nanoparticles have been identified as a metal electrocatalyst exhibiting high mass activity [7,8]. In order to understand the enhanced performance of these catalysts, knowledge of how the two elements forming the bimetallic compound are distributed at the atomic level is important.