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I achieved all of the primary goals outlined in my proposal, although the path differed somewhat from what I initially conceived.  My research group has focused on developing a new method for preparing heterogeneous catalysts using nanoparticles prepared with solution techniques..  The primary goals of the sabbatical were for me to find / develop new reactions to study with our unique methods, ideally in the area of green chemistry.  Additionally, I planned to learn basic synchrotron techniques and develop collaborations that would allow us to perform EXAFS and XANES studies in the future.    

The original plan was to spend 6 months at the Danish Technical University (DTU) working in the Center for Green Chemistry (CGC), followed by 6 months at the University of Utrecht learning EXAFS.  Unfortunately, 3 weeks before I arrived, my host at DTU left the institution for another position.  Although I maintained connections with the CGC I shifted my primary research to the Physics Department, performing computational studies with Jens Nørskov, who is arguably the top computational catalysis researcher in the world.

In Nørskov’s group, I studied the effects of incorporating heterometals in to Au(111) structures, using them as simple models for bimetallic nanoparticles.  This is an especially efficient means of evaluating the degree to which bimetallic Au-based nanoparticles might have new catalytic properties.  To make the calculations amenable to screening a large number of metal combinations, we calculated the adsorption energies on Au(111) surfaces in which the subsurface metal layer was replaced with a transition metal.  We initially studied oxygen and CO adsorption, but extended the study to include OH, NH₂, CH₃, H, NH₃, CH₃OH, and H₂O. 

The adsorbates were screened on more than 15 bimetallic Au-M alloys (Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd, Ag, Cd, W, Re, Os, Ir, & Pt), and a number of trends quickly emerged.  The most important trend was that as earlier (more oxophillic) transition metals were incorporated into the Au lattice, the adsorption energy of oxygen (and to a lesser extent, CO) increased.  Although this seems reasonable to predict, the exact opposite trend (decreased oxygen binding when earlier transition metals are incorporated as the subsurface monolayer) is observed for Pt based alloys, both computationally and experimentally.  This ultimately led us to investigate the Au system more deeply, and eventually conclude that charge transfer from the heterometal to the more noble metal plays a larger role in affecting adsorption energies than was previously realized.      

The research at DTU was quite successful.  I recently submitted one manuscript to Angewandte Chemie based on some experimental work with NiAu alloys prepared in my lab at Trinity, which included supporting calculations.  In addition, we are preparing to submit a communication to JACS based on the Au results and a large theory paper (probably for J. Chem Phys) that incorporates both the Pt-M and Au-M results in the context of the widely used d-band model for metal alloys. 

The computational studies highlight clear avenues for the future direction of research in my group.  We now have a sense as to both how heterometals affect the chemistry of Au and how much of a change we might expect to see with different bimetallic combinations.  This leads to a number of very clear research projects, and provides substantial directions regarding which metal combinations should be tried first (i.e. which are likely to have the largest effects).  My research group is now beginning to test the computational predictions using reactions, equipment, and characterization tools already available at Trinity.  I am also writing an NSF proposal that will allow us to follow up on the sabbatical studies and develop some new experimental tests for the computational models.  Further, because the computational studies point to some metal combinations as potential catalysts in couple high impact industrial reactions, I expect to develop a DoE proposal later this academic year. 

The PRF supported leave also allowed me to present seminars at several Universities in Europe and develop a number of collaborations.  Working with a colleague at Trinity, we have started to perform CO adsorption studies on a series of PdAu catalysts for Prof. Catherine Louis at the Pierre and Marie Curie Institute in Paris.  I will also be hosting a visiting scientist from the University of Milano in January.  Dr. Della Pina will characterize some of her catalysts and we will begin kinetic modeling of some of her results.  Additionally, next summer my research group will begin preparing some bimetallic catalysts for Prof. Gadi Rothenberg at the University of Amsterdam. 

Even though I was not able to learn the synchrotron techniques I originally proposed, I was able to develop a new collaboration with Dr. Jeff Miller at Argonne National Lab.  Dr. Miller and I met at a conference in Heidelberg, Germany and discussed a number of mutual interests.  We have continued our discussions this year, and I will travel to Argonne in October to give an informal seminar and discuss future research directions with Dr. Miller and Prof. Fabio Ribiero (Purdue).  This will provide new opportunities for my research group to access the National Light Source at Argonne, allowing us to do EXAFS and XANES experiments. 

Although the sabbatical did not go exactly as initially planned, it was extremely successful in moving my research program forward.  Beyond the tangible benefits described above, the year gave me time to focus on research and carefully consider where I can best spend my time and energy for the next several years.  Particularly at a small PUI, where we teach essentially year round (academic year and 10 week summer research program), time to collect thoughts and plan for the future is invaluable.  My research program is unquestionably better off thanks to the support of the PRF.