Time: September 22th, 2017, 9:00am
Venue: No.2 Conference Room in Energy Building Conference Center
Lecturer: Michael S. Wong Ph.D., Rice University
Dr. Michael S. Wong is Professor and Chair of the Department of Chemical and Biomolecular Engineering at Rice University. He is also Professor in the Department of Chemistry, Department of Civil and Environmental Engineering, and Department of Materials Science and NanoEngineering. He was educated and trained at Caltech, MIT, and UCSB before arriving at Rice in 2001. His research program broadly addresses chemical engineering problems using the tools of materials chemistry, with a particular interest in energy and environmental applications ("catalysis for clean water"). He has received numerous honors, including the MIT TR35 Young Innovator Award, the American Institute of Chemical Engineers (AIChE) Nanoscale Science and Engineering Young Investigator Award, Smithsonian Magazine Young Innovator Award, and in 2015, the North American Catalysis Society/Southwest Catalysis Society Excellence in Applied Catalysis Award. He is a Research Thrust Leader in the NSF-funded NEWT (Nanotechnology Enabled Water Treatment) Engineering Research Center. He is the 2016-2017 Chair of the ACS Catalysis Science and Technology Division, and serves on the Applied Catalysis B: Environmental editorial board.
Nitrate (NO3-) is an ubiquitous groundwater contaminant, and is detrimental to human health. Bimetallic palladium-based catalysts have been found to be promising for treating nitrate (and nitrite, NO2-) contaminated waters. Those containing indium (In) are unusually active, but the mechanistic explanation for catalyst performance remains largely unproven. We report that In deposited on Pd nanoparticles (NPs) ("In-on-Pd NPs") shows room-temperature nitrate catalytic reduction activity that varies with volcano shape dependence on In surface coverage. The most active catalyst had an In surface coverage of 40%, with a pseudo-first order normalized rate constant of kcat ~ 7.6 L gsurface-metal-1 min-1, whereas monometallic Pd NPs and In2O3 have nondetectible activity for nitrate reduction. X-ray absorption spectroscopy (XAS) results indicated that In is in oxidized form in the as-synthesized catalyst; it reduces to zerovalent metal in the presence of H2 and re-oxidizes following NO3- contact. Selectivity in excess of 95% to nontoxic N2 was observed for all the catalysts. Density functional theory (DFT) simulations suggest that submonolayer coverage amounts of metallic In provide strong binding sites for nitrate adsorption and they lower the activation barrier for the nitrate-to-nitrite reduction step. This improved understanding of the in active site expands the prospects of improved denitrification using metal-on-metal catalysts.
Contact: JIANG Hong DNL0602