Comparison Between Electrocatalysis and Heterogeneous Catalysis

Electrochemistry is the surface science studying the physicochemical phenomena at the interface between an electrode and the electrolyte. The aim of electrocatalysis is to accelerate electrochemical reactions taking place at the electrode surface. 

The most important parameters in electrocatalysis are the overpotentials, which arise from the losses due to the kinetics at the electrodes and transport losses in the electrolyte. The goal is to have low overpotentials r/i at high currents. In electrocatalysis the current is referred to the electrode surface thus obtaining the current density j. The dependence between overpotentials t] and current density j is described by the Tafel equation (Eq. 9-1) 

Industrial Catalysis A Practical Approach, Second Edition Jens Hagen Copyri t 2006 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-31144-0 

Electrocatalysis is the phenomenon tiiat electrode reactions can be accelerated by structural or chemical modification of the electrode surface and by additives to the electrol5fte. Structural modifications include changes in surface geometry (crystal planes, clusters, adatoms), and variations in die electronic state of the catalyst material. Electrode reactions are connected widi a transfer of electric charge carriers through the interface between the electrode and the electrolyte. These charge carriers can be ions or electrons. 

These electric forces can be charactrized by the so-called electrode potential relative to a suitable reference electrode which can be altered in an electrolysis cell by an external voltage applied to this cell. A great advantage is that the rate of the reaction can be followed with high sensitivity in the form of the electric current passing the electrode interface. 

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