Methods for Characterizing Adsorption on Solid Surfaces in Liquids

The recent surge in basic research studying liquid-phase surface reactions for catalytic biomass conversions and electrocatalytic reactions for energy storage and utilization highlights the importance of characterizing adsorbates at the liquid / solid interface and their surface chemical reactions. The design of new, more active, and selective catalysts for these reactions is vital. Typical catalytic reactions include multiple elementary steps involving many surface-bound intermediates and transition states. The energetics of these intermediates and transition states are crucial, as they determine the rate and selectivity of the catalysts. These energies are also essential to build accurate microkinetic models that predict activity and selectivity under different conditions and the few rate-controlling species whose energies can be tuned to make a better catalyst. Therefore, the ability to identify the adsorbed intermediates in catalytic reaction mechanisms and to predict the energies of these surface intermediates and their transition states for formation and further reaction are of critical importance. This is true for reactions at solid surfaces both in the gas phase and in liquids. We review here methods for studying adsorbates on solid surfaces in the liquid phase, their coverages, the rates of their formation and further surface reactions, the internal energies of these adsorbates, the activation free energies for their formation, and methods for estimating the effects of solvent choice and of interfacial electric fields on these adsorbate internal energies.