(3r) Rational Catalyst Design/Synthesis and Application for Renewable Chemical Production

Rational catalyst design/synthesis and application for renewable chemical production

Weijian Diao

Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina

Research Interests:

Bimetallic catalysts offer potential of improved catalyst performance with enhanced activity and/or selectivity, longer catalytic lifetimes. Bimetallic catalysts can combine monometallic behavior to give sites with new properties with ensemble effect (dilution of active metal by inactive metal), Electronic effect (e- transfer between two metals) and bifunctional effects (each metal is catalytically active). However conventional methods for bimetallic catalyst synthesis including co-impregnation and successive impregnation result in the formation of monometallic particles from each metal salt as well as bimetallic particles with varying compositions of the two components. With poor control of the final catalyst composition and structure, it is very difficult to correlate between catalyst performance, catalyst characterization, and catalyst composition.

Electroless Deposition method

In my research, a unique synthesis method called Electroless Deposition (ED) is used for synthesis of bimetallic catalyst with true bimetallic surface and controllable surface composition. Electroless Deposition (ED) is a catalytic or autocatalytic process for deposition of metals by the pre-existing metal (catalysis) or the metal which is being deposited (auto-catalysis).

We start with a monometallic catalyst and typical organic reducing agent including HCHO, N₂H₄, DMAB, H₂PO₂^-, HCOOH, HCOOH, BH₄^-. The reducing agent is only activated on primary metal surface which leads to targeted deposition of secondary metal B on primary metal A. This process can be repeated on primary metal A which leads to catalytic deposition and fresh deposited secondary metal B which leads to autocatalytic deposition.

We have been using Electroless deposition method to synthesize different bimetallic catalysts including Pt-Ru, Pd-Ag, Pd-Au, Pt-Ir, Pt-Co, Pt-Co. Strong metal-metal interactions and bimetallic surface offer significantly improved performance for many different application including direct methanol fuel cell (DMFC), hydrogen production, selective oxidation/hydrogenation reactions.

Galvanic Displacement (GD) method

Galvanic Displacement (GD) is also been used in my research for preparation of bimetallic catalysts with highly-dispersed even single atom secondary metal on primary metal. Galvanic displacement takes place when the base material is displaced by a metallic ion in the solution having a lower oxidation potential than the displaced metal ion. GD is one atom to one atom process which offers possibility of isolated secondary metal atoms on primary metal. No reducing agent is required which makes suitable for large scale synthesis. We have successfully use GD method for Pd-Ag, Pd-Cu and Pt-Cu synthesis which provide unique properties due to extremely small ensemble sizes.

Strong Electrostatic adsorption (SEA) method

Strong Electrostatic adsorption (SEA) is synthesis method for highly-dispersed, extra small particle size monometallic and bimetallic catalysts by inducing surface charge on support by adjusting pH of impregnating solution. With adjusting pH of impregnation solution, a close packed monolayer of ionic complex (retaining hydration sheaths) with strong interaction with support was formed which decreased mobility of metal atoms result in smaller catalyst particles. It is a scalable synthesis method to synthesize 1-1.5nm support metal catalysts. Our study shows uniform distributed, highly-dispersed Pt, Pd, Au, Ag, Ir, Rh, Co, Cu as well as Pt-Co, Pd-Cu, Ag-Ir, Pt-Pd, Au-Ag catalysts can be synthesized on SiO₂, Al₂O₃, TiO₂, carbon, graphene and zeolites.

Funded projects:

(Total amount of projects as PI and Co-PI is more than $1,500,000. Specific amount for Dr. Diao is more than $650,000)

Principal Investigator:

1. S. National Science Foundation (NSF), Industry–University Cooperative Research Centers Program (IUCRC) of Center for Rational Catalyst Synthesis (CeRCaS), “Boron nitride (BN) supported metal and metal oxide catalysts for selective oxidation reactions”, 06/2018-12/2020
2. S. Department of Energy (DOE), Laboratory Directed Research and Development (LDRD), “Catalysts development for water splitting reactions using solid oxide electrolysis cells (SOECs)”, 03/2019-09/2020
3. Southwest Research Institute, "Development and Characterization of Novel Catalyst for Automotive Emissions Applications", 11/2019-07/2020
4. Industrial Company, one of top ten largest chemical company and chemical producers “Mixed metal oxide catalysts development for oxidative dehydrogenation (ODH) of ethane to ethylene”, 10/2019-09/2020

Co-Principal Investigator:

1. S. Department of Energy (DOE), Laboratory Directed Research and Development (LDRD), “Kinetic-based Scale-Up Science for an Energy Efficient Route to Ethylene”, 06/2016-09/2017
2. University of South Carolina, Advanced Support for Innovative Research Excellence (ASPIRE) III, “In situ high temperature and variable gas environment X-ray Diffractometer for study of effects of temperature and gas environment on stability of catalysts and other novel materials”, 07/2018-09/2019
3. S. National Science Foundation (NSF), Industry–University Cooperative Research Centers Program (IUCRC) of Center for Rational Catalyst Synthesis, “Computational and experimental analysis of Ag catalysts with GNP or bimetallic materials on direct propylene oxide synthesis”, 06/2019-09/2020

Teaching Interests:

I passionately believe that teaching is a key and enjoyable part of being a new faculty member. I view teaching not only providing knowledge and information, but more about inspiring students who are future engineers, scientists and professors. I am excited about the opportunity to teach both undergraduate and graduate level classes as well as mentoring graduate and undergraduate students laboratory experiments. As a post-doc at Idaho National Laboratory and a research assistant professor at University of South Carolina, I have supervised graduate and undergraduate students in the catalysis and energy related projects with more than five publications.

Also, I have served as lecturer and teaching assistant for undergraduate and graduate courses during my PhD, post-doc and research assistant professor studies since 2011. I heavily participated in giving lectures, designing course contents and preparing grading exam questions and homework problems for courses including Chemical Process Principles, Chemical Engineering Thermodynamics, Heterogeneous Catalysis, and Chemical Engineering Undergraduate Laboratory. I am excited to share the fundamental science in chemical engineering and its significant impact on latest technology in industry and our daily life with undergraduate students to help cultivate their interests for science and engineering, and contribute to their education and professional career development.

Specific courses I would particularly enjoy teaching include Chemical Engineering Fundamentals, Chemical Process Principles, Chemical Reaction Engineering, Materials Characterization, and Chemical Engineering Thermodynamics at both undergraduate and graduate levels. In addition, with background of heterogeneous catalysis, I also plan to develop an elective course introducing the fundamentals of catalysis, including catalyst preparation and evaluation, reactor design, kinetic studies, mass/heat transfer limitations, and mechanism study using advanced characterization.