Recent developments and trends in the electrochemical promotion of catalysis (EPOC)

Electrochemical Promotion of Catalysis (EPOC or NEMCA effect) is one of the most exciting discoveries in Electrochemistry with great impact on many catalytic and electrocatalytic processes. According to the words of John O'M. Bockris, EPOC is a triumph, and the latest in a series of advances in electrochemistry which have come about in the last 30 years. It has been shown with more than 80 different catalytic systems that the catalytic activity and selectivity of conductive catalysts deposited on solid electrolytes can be altered in a very pronounced, reversible and, to some extent, predictable manner by applying electrical currents or potentials (typically up to +/- 2 V) between the catalyst and a second electronic conductor (counter electrode) also deposited on the solid electrolyte. The induced steady-state change in catalytic rate can be up to 135 x 10(3)% higher than the normal (open-circuit) catalytic rate and up to 3 x 10(5) higher than the steady-state rate of ion supply. EPOC studies in the last 7 years mainly focus on the following four areas: Catalytic reactions with environmental impact (such as reduction of NO (x) and oxidation of light hydrocarbons), mechanistic studies on the origin of EPOC (using mainly oxygen ion conductors), scale-up pf EPOC reactors for potential commercialization via development of novel compact monolithic reactors and application of EPOC in high or low temperature fuel cells via introduction of the concept of triode fuel cell. The most recent EPOC studies in these areas are discussed in the present review and some of the future trends and aims of EPOC research are presented.