Single‐Crystal Adsorption Calorimetry on Well‐Defined Surfaces: From Single Crystals to Supported Nanoparticles

Abstract

Single-crystal adsorption calorimetry (SCAC) measures the energetics of gas-surface interactions in a direct way and can be applied to a broad range of well-defined model surfaces. In this Personal Account we review some of the recent advances in understanding the interaction of gaseous molecules with single-crystal surfaces and well-defined supported metallic nanoparticles by this powerful technique. SCAC was applied on single-crystal surfaces to determine formation enthalpies of adsorbed molecular fragments typically formed during heterogeneously catalyzed reactions involving hydrocarbons. On supported metal nanoparticles, the binding energies of gaseous species were determined by SCAC as a function of the particle size. The reported data provide valuable information for ongoing research in many fields of heterogeneous catalysis and materials science. In addition, direct calorimetric measurements serve as benchmarks for the improvement of computational approaches to understanding surface chemistry.

Binding Energy and Diffusion Barrier of Formic Acid on Pd(111)

“…Although many methods have been applied to determine binding energies, single crystal adsorption calorimetry (SCAC) in combination with sensitive pyroelectric detectors has proven itself to be one of the most reliable tools. − A special challenge arises for binding energies of highly reactive molecule/surface systems. For SCAC, experimental conditions have to be carefully chosen such that either molecular adsorption or decomposition reactions dominate; only then can the heat release be used to derive binding energies.…”

Experimental characterization of the energetics of low-temperature surface reactions

“…In this way, the method exploits the same approach as was used in the pioneering studies by Yuan Lee to characterize gas-phase reactions by crossed molecular beam techniques 10,11 . So far, the calorimetric techniques available to study surface reactions, like single crystal adsorption calorimetry or isothermal titration calorimetry, provide the enthalpy of the reactions of molecules with a surface 12 . To the best of our knowledge, there is still no universal technique available that allows us to precisely measure the amount of energy released in surface reactions of a single pair of reactants.…”

Water and Carbon Dioxide Adsorption on CaO(001) Studied via Single Crystal Adsorption Calorimetry

“…In this connection, the central technique in the present study is microcalorimetry, and the associated data evaluation. For a typical single crystal adsorption calorimetry experiment [14,15], the heat release for a molecular beam pulse is derived from comparison of the slope of the initial steep rise [16], or the absolute peak height [17][18][19] of the heat detector's signal in comparison with the corresponding value for a laser reference pulse. This procedure requires that the line shape for molecular beam and laser pulse measurements are congruent.…”