(6cg) Development of n-Doped Oxides As an Electron Rich Support: Bridging Homogeneous and Heterogeneous Catalysis

As the need for sustainable chemical processes is rapidly increasing, a renewed focus has been placed on increasing the energy efficiency of chemical processes. By far the most energy intensive process in any homogeneously catalyzed process is the recovery of the catalyst, usually a precious noble metal, from the product mixture. Typical processes which utilize homogeneous catalyst, such the creation of active pharmaceutical ingredients (APIs) and olefin hydroformylation to make block co-polymers, yield poor energy efficiencies due to their intense separation processes, and often yield detrimental effects to the product if residual catalyst remains. One of the key factors to active homogeneous catalysts is their rich electron density, often achieved via the use of intricate ligands that allow the clearly defined active site to freely undergo the required redox cycles to form the desired product. Due to the innate variability of active sites on heterogeneous catalysts, their use in processes that require highly pure products has been limited; however, if the supporting material can be engineered to have energetically preferential grafting sites for metal precursors, not only can the heterogeneity of the surface be mitigated but the functionality of the support can dramatically be changed.

To develop next generation supporting oxides for heterogeneous catalysis the use of n-doped oxides will be explored. Doping semiconducting materials, such as silicon, is a mature field; however, these novel applications which alter the electronic properties of the support have not been carried into heterogeneous catalysis. By incorporating n-doped species, such as phosphorus, we can not only provide preferential adsorption sites for metal precursors during synthesis, but also provide electron rich ligands to promote metal support interactions, thus facilitating the intricate redox cycles required for homogeneous catalysts without the need for extensive energy use needed for catalysts recovery. In this proposal, the use of rhodium catalysts for ethylene hydroformylation will be explored as a model reaction for the use of phosphorus doped silica and compared against typical homogeneous catalyst, therefore providing a bridge between heterogeneous and homogeneous catalysts. This work will lay the foundation to attempt to address one of the key challenges laid out by the Catalysis Science focus area of the Chemical Science, Geoscience, and Biosciences Division of the Department of Energy, which is the convergence of heterogeneous and homogeneous catalysts. The initial work, focusing on simpler model systems such as phosphorus doping into silica over Co/Rh catalysts for light olefin hydroformylation, will then be carried out to more complex systems such as industrially relevant reactions like the enantioselective hydroformylation of styrene to vinyl acetate over several electronically modified supports such as n/p-doped silica, titania, or zirconia.

During my PhD at the University of South Carolina under the supervision of Prof. Jochen Lauterbach, I have developed a broad skillset to develop precise catalytic materials with well controlled active sites. Furthermore, by employing various characterization techniques, such as in situ X-Ray Absorption, infrared, and Raman spectroscopy; I was able to probe the catalysts under working conditions. The intricate use of spectroscopic techniques allowed me to probe the CO₂ hydrogenation reaction mechanism over facet controlled cobalt nanorods, discern the local structure of single site cobalt and ruthenium catalysts under relevant conditions, and gain insight into the structure of mixed metal oxide catalysts for ethane partial oxidation. Additionally, under the supervision of Prof. Kiyotaka Asakura at the Institute of Catalysis at Hokkaido University, I was able to further refine my knowledge of XAFS by carrying out operando High Energy Resolution Fluorescence Detection (HERFD) XANES and simultaneously developed a corresponding model of the catalyst under working conditions via FEFF8, helping verify our experimental findings. This study was carried out on a platinum-gold bimetallic electrocatalyst where HERFD XAFS was coupled with ab initio FEFF8 calculations to discern the surface species present on the Pt surface. Working with diverse chemical systems and catalyst compositions at these distinct research institutions has given me perspective on how to independently develop novel projects, where I have learned how to leverage my skillset to explore a diverse set of catalytic systems.

Relevant Publications († denotes equal contribution first author):

1. Jimenez, J.D.; Jung, S.; Biddinger, E. J., Ionicity Analysis of Silylamine-Type Reversible Ionic Liquids as a Model Switchable Electrolyte. Journal of the Electrochemical Society 2015, 162 (7), H460-H465.
2. Jimenez, J.; Bird, A.; Santos Santiago, M.C.; Wen, C.; Lauterbach, J., Supported Cobalt Nanorod Catalysts for CO₂ Hydrogenation. Energy Technology 2017, 5, 884-891
3. Wu, J.; Wen, C.; Zou, X.; Jimenez, J.; Sun, J.; Xia, Y.; Fonseca Rodrigues, M.-T.; Vinod, S.; Zhong, J.; Chopra, N.; Odeh, I. N.; Ding, G.; Lauterbach, J.; Ajayan, P. M., Carbon Dioxide Hydrogenation over a Metal-Free Carbon-Based Catalyst. ACS Catalysis 2017, 4497-4503
4. Jimenez, J.D.^†; Mingle, K.^†; Bureerug, T.; Wen, C.; Lauterbach, J. Statistically Guided Synthesis of MoV- Based Mixed Oxide Catalysts for Ethane Partial Oxidation. Catalysts 2018, 8, 370-386. Selected as a Featured Paper
5. Jimenez, J.D,; Wen, C.; Lauterbach, J.; Design of Highly Active Cobalt Catalysts for CO₂ Hydrogenation via the Tailoring of Surface Orientation of Nanostructures. Catalysis Science & Technology, 2019, 8, 1970-1979
6. Fan, M.^†; Jimenez, J.D.^†; Shirodkar, S.N.; Wu, J.; Chen, S.; Royko, M.; Song, L.; Zhang, J.; Guo, H.; Cui, J.; Zuo, K.; Wang, W.; Zhang, C.; Vajtai, R.; Qian, J.; Yang, J.; Yakobson, Y.I.; Tour, J.M.; Lauterbach, J.; Sun, D.; Ajayan, P.M. Ru Atoms Immobilized on Porous h-BN for Highly Active and Selective CO₂ Methanation. ACS Catalysis, In Revision
7. Jimenez, J.D; Wen, C.; Royko, M.; Kropf, A.J.; Segre, C.; Lauterbach, J. Influence of coordination environment around anchored single-site cobalt catalyst for CO₂ hydrogenation. In Preparation.

Teaching Interests:

As teaching at both the undergraduate and graduate level is an essential part of being a faculty member, it is something I have always taken interest in. Beginning in my undergraduate at the City College of New York holding introductory chemistry workshops, I learned early on the importance of effectively communicating various topics. My interest in teaching was further expanded during my PhD at the University of South Carolina, where I served as a Teaching Assistant for both undergraduate and graduate courses, often holding both recitations and full classes for the graduate level Mass Transfer course at USC. One of the key things I have learned in the classroom, through both my experience teaching and being a student, specifically a first generation Hispanic student, is the need for individualized teaching and reaching out to students to ensure the content is not only understood; but that students are properly mentored on their prospective career paths. To this end, I have made it a priority to mentor students all throughout my graduate studies, both undergraduates and junior graduate students, not only showing them the required theories and techniques to succeed, but to instill in them a strong sense of scientific independence. Furthermore, as part my National Science Foundation Integrated Graduate Research Traineeship (NSF-IGERT) I have developed a strong set of soft skills, that include consideration of the patent process and its various levels, collaborating with local politicians to push public policy reform, and presenting highly technical work to a diverse non-technical audience. With this in mind, I would incorporate public policy outreach into my classes, such as including public policy discussion into senior level undergraduate design courses. Additionally, I can host a new class that is taught at both the undergraduate and graduate level that addresses technoeconomic analysis and would include a considerable amount of outreach to local government so that students can see how policy shapes what can and can’t be implemented commercially.