A Model for Oscillating Hydrogen Liberation at CuInSe 2 in Presence of H 2 O 2 Ludwig Pohlmann * , Günther Neher, and Helmut Tributsch * Hahn-Meitner-Institut, Dep. Solare Energetik, Glienicker Strasse 100, D-14109 Berlin, Germany Abstract It is shown that hydrogen evolution can be obtained far from equilibrium as an oscillating mechanism during the electrochemical reduction of hydrogen peroxide at copper-containing semiconductor electrodes. Periodic hydrogen evolution was experimentally verified by in-situ Differential Electrochemical Mass Spectroscopy (DEMS). We report a working mechanistic model accounting for the most relevant features of the experimental system. Some of the novel possibilities for electrocatalysis arising from far from equilibrium nonlinear processes in presence of autocatalysis are discussed. Introduction The classical hydrogen evolution reaction has been called the „archetype“ for the study of electrochemical reactions, since it involves simple versions of features which are met in nearly all of them 1 . It is indeed a reaction which comes very close to the condition of thermodynamic reversibility, as supported by ample experimental evidence.