Influence of the electrolyte composition on the activity and selectivity of electrocatalytic centers

The capability to efficiently design new electrocatalytic materials depends on a deeper understanding of all factors influencing the performance of active sites under reaction conditions. While the electrode surface structure and composition are primary, the role of electrolyte components in the activity and selectivity of catalytic centers is also significant, if not drastic. Interestingly, the performance of electrocatalysts is not only affected by the so-called specifically adsorbing ions. Many species, which are generally considered "inert", can de facto change the key properties of the catalytic sites. However, the origin of such experimentally observed effects is often poorly understood. Despite the fact that certain trends are frequently observed, further investigation of model systems and development in the field of quantum chemistry calculations are necessary in order to gain deeper insight into the effects of the electrolyte composition. The goal of this review article is to summarize and analyze recent achievements in the elucidation of the non-trivial effects of electrolyte components and their contribution to the observed performance of catalytic centers. A particular focus is set on the influence of (i) alkali metal cations, (ii) commonly used anions, (iii) unexpected pH effects, as well as (iv) the impact of certain ionic liquids on the activity and selectivity of catalytic systems. Reactions which are essential for the prospective sustainable energy provision schemes are selected as illustrative examples. (C) 2015 Elsevier B.V. All rights reserved.