ReactorSTM : imaging catalysts under realistic conditions

This thesis describes the construction of a second generation high-pressure, high-temperature scanning tunneling microscope, the ReactorSTM, with which the surfaces of catalysts can be studied under relevant reaction conditions. Furthermore, the thesis describes three separate catalytic systems at ~ 1 bar, and elevated temperatures. Firstly, NO reduction on Pt(100), in which a mathematical model for the reaction mechanism, following Langmuir-Hinshelwood kinetics, is proposed. Secondly, CO oxidation, in which the Pt(110) surface is atomically resolved at high p, T. Thirdly, the thesis describes a successful pilot experiment about the hydrodesulphurization of thiophene, which is catalytically activated by molybdenum disulphide nano-crystallites on an Au(111) support.LEI Universiteit LeidenNanoNed (www.nanoned.nl) NIMIC (www.realnano.nl)Quantum Matter and Optic

High-pressure operando STM studies giving insight in CO oxidation and NO reduction over Pt(110)

AbstractTwo catalytic systems have been studied at high pressures on the Pt(110) surface on an atomic level. The first system was the oxidation of CO by O2 towards CO2. In the framework of the second reaction, namely NO reduction, the effect of room temperature exposure of the surface to NO and H2 was investigated. To study these reaction systems at relevant pressures, the ReactorSTM has been used. This is a unique system which consists of a compact STM in which a flow reactor is integrated. The combined reactor with STM is housed inside a conventional vacuum system to allow for traditional surface science preparation and analysis techniques. The STM images obtained with the ReactorSTM under reaction conditions show the lifting of the (1x2) missing row reconstruction by high-pressure CO exposure. The lifting is followed by the formation of the (1x1) metallic Pt(110) structure for high CO/O2 ratios and a (1x2) lifted-row type surface oxide structure for more O2-rich conditions. The room temperature exposure of Pt(110) to H2 results in the formation of a (1x4) missing-row structure and deeper, nested missing rows. The exposure to high-pressure NO removes these missing-row structures

The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions

Quantum Matter and Optic

Preparing for science run 1 of MiniGRAIL

We report on the eighth cryogenic run of MiniGRAIL, which is planned to be the first science run. Three new capacitive transducers were mounted on the sphere, all coupled to superconducting transformers and a double-stage SQUID amplifier. All SQUID modules had a noise level between 1 and 2 μΦ0 Hz−1/2 at 4 K in separate test runs. The detector was upgraded with a complete data acquisition and data storage system, and a data analysis program for millisecond burst signals was written using a matched filter. Two cosmic-ray detectors were built and installed on the roof above MiniGRAIL as a veto for cosmic rays. A test run was done, but failed because of bad electrical isolation of the transducer electrode at low temperatures. A new cool-down is currently going on. With an already obtained sphere temperature of 65 mK and a SQUID noise of 100, the expected sensitivity should be 4 × 10−22 Hz−1/2