EXPLORING SOLID-LIQUID INTERFACIAL CHEMISTRY DURING CATALYST SYNTHESIS

1. EXPLORING SOLID-LIQUID INTERFACIAL CHEMISTRY DURING CATALYST SYNTHESIS Christopher T. Williams, John R. Monnier, John R. Regalbuto USC Center for Rational Catalyst Synthesis Planning Grant Workshop University of South Carolina, Columbia, SC June 16, 2014

2. Exploring Solid-Liquid Interfacial Chemistry During Catalyst Synthesis Research Team: Williams, Monnier, Regalbuto (USC) Overview: Probe surface chemistry during SEA and ED processes to facilitate optimization of bimetallic catalyst synthesis hn Technical Information: in-situ surface vibrational (FTIR, Raman) spectroscopy; optimization of catalyst synthesis process. Industrial Relevance: Precise control of synthesis

3. Industrial Relevance Producing Bimetallic Catalysts with Small Particle Sizes Minimize Metal Usage in Bimetallic Catalysts

4. Goals of the Proposal • Use Attenuated Total Reflection Infrared (ATR-IR) and Raman spectroscopies to explore surface chemistry during ED and SEA synthesis of bimetallic catalysts • Correlate surface speciation with ED and SEA synthetic parameters and resulting catalyst properties • Develop strategies to overcome limitations and enhance performance of the approaches

5. Proposal Hypotheses • Adsorption of chemical species from solution plays key roles in ED • stabilizers; reducing agents (e.g., formaldehyde, DMAB, NaBH4), also in their oxidized forms and their fragments, e.g., CO; • varying extents/strengths of adsorption on various metals helps to determine the selectivity of autocatalytic vs. catalytic deposition • adsorbed species can result in sintering of small nanoparticles due to enhanced mobility of atoms (e.g., metal complexes) • The stability of surface oxides during sequential SEA methods is a key determining factor in its success • adsorption of precursors onto support and first metal oxide can result in alteration of the oxide • formation of mixed oxides during the activation treatment will effect eventual properties of reduced bimetallic particles • Correlation of surface speciation (measured with spectroscopy) and solution-phase parameters (measured during synthesis) can be coupled to generate predictive models

6. Research Methods/ Techniques In-Situ ATR-IR and Raman of Support/Catalyst Films in the Liquid Phase In-Situ Raman During Gas-Phase Activation of Catalysts

7. Outcomes/ Deliverables – Year 1 • Mn-Rh/SiO2 synthesis by SEA explored by Raman • Liquid-phase adsorption of MnO4- species onto supported Rh2O3 under different solution-phase conditions • Gas--phase calcination/reduction of SiO2-supported MnO4-/MnO4-/Rh2O3 particles • Correlation of surface speciation with resulting bimetallic particle structure • Ag-Pt/X (X=SiO2,Al2O3) synthesis by ED explored by ATR-IR • Adsorption/activation of reducing agents - formaldehyde, hydrazine, dimethylamine borane - on Pt catalysts, bare supports, and Pt metal • ED of AgNO3 onto Pt catalysts and Pt metal under different conditions • Influence of adsorbed CO on the speciation during ED process • Correlation of surface speciation with deposition limits and sintering observed in batch and/or continuous ED experiments • Longer Term Plans (beyond first year) • Extension to other SEA/ED synthetic systems as suggested by EAB • Development of predictive models based on surface chemistry insight

8. Impact • Improved understanding of surface chemical factors that may hinder implementation of SEA and ED in industry • Enhanced catalyst properties at reduced cost? • Establishment of in-situ solid-liquid interface techniques that can address needs of EAB members • ATR-IR can be applied to a broad range of liquid-phase adsorption and reaction processes relevant to catalytic materials synthesis Duration of Project and Proposed Budget • 1 year @ $60,000 • $60,000/yr thereafter, expanding to other systems as desired