Physical Sciences Division
Bob applies synthetic, spectroscopic, analytic, and kinetics measurements and reactor engineering to devise microkinetic models of the networks of elementary steps to represent the rates of heterogeneously catalyzed reactions. The microkinetic approach encourages the development of structure/activity relationships, helps focus experimental work, and facilitates archiving and re-using kinetic motifs across varied sets of applications and reaction conditions.
Currently, his kinetic modeling efforts and experimental activities focus on reactions in condensed media, where bulk and local polarizability can alter the energetics of charged and polar intermediates, compared with their stabilities in reaction media that have low dielectric constants. The immediate applications are the upgrading reactions of the oxygen-containing intermediates produced by thermochemical processing of biomass into fuel precursors and the electrochemical and photochemical transformations of organic molecules into active pharmaceutical ingredients.
He has proposed to use solvatochromism of luminescent surface-supported chromophores to probe the cybotactic region at the interface of complex reaction media with the surfaces of supported metal catalysts. In recent work, he found catalysts that exhibit strong solvatochromic shifts and parallel, strong changes in the activation of hydrogen. He inferred from the data that the catalyzed transfer of hydrogen involves heterolytic bond breaking and formation. He has used models of the cybotactic region to motivate the definition of a new type of support effect: The "Mr. Rogers Support Effect" refers to catalyzed systems in which the support differentially attracts substrates to the neighborhood of the catalytic site.