David King and his group developed the first calorimeter that could measure heats of adsorption on the well-defined surfaces of single crystals with sufficient precision to reveal new understanding of surface chemistry, especially by determining the energies of adsorbed molecular fragments that are catalytic reaction intermediates and otherwise inaccessible experimentally. Since then, our group has adopted this technique and made substantial improvements in heat detection, allowing routine measurements from 100 to 350 K with high precision (±1.3 kJ/mol in the heat for adsorbing 1% of a monolayer) and accuracy (2-3 %). We have applied it to measure the heats of formation of well-defined adsorbates on single crystal metal surfaces, including Pt(111), Ni(111) and Cu(111). Those results will be reviewed, with emphasis on the new insights they provide regarding reaction mechanisms and the differences in catalytic activity between different metals. The applications of these energies as benchmarks for assessing the energy accuracy of quantum mechanical approximations like those in density functional theory (DFT) reveal substantial errors in the relative energies of adsorbed catalytic reaction intermediates, even with the best DFT methods.<br/>

Heats of formation of adsorbed catalytic intermediates on well-defined surfaces by single crystal adsorption calorimetry

2019 Spring National Meeting

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