Two catalytic systems have been studied at high pressures on the Pt(1 1 0) surface on an atomic level. The first system was the oxidation of CO by O-2 towards CO2. In the framework of the second reaction, namely NO reduction, the effect of room temperature exposure of the surface to NO and H-2 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(1 1 0) structure for high CO/O-2 ratios and a (1x2) lifted-row type surface oxide structure for more O-2-rich conditions. The room temperature exposure of Pt(1 1 0) to H-2 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. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-SA license