Gary L. Haller

Henry Prentiss Becton Professor of Engineering and Applied Science
Professor of Chemistry
Member of Yale faculty since 1967

E-mail: gary.haller@yale.edu
Web site: http://www.eng.yale.edu/faculty/vita/haller.html

Research The goal of our research has been to understand and rationalize heterogeneous catalytic activity and selectivity in terms of surface or deduced site structure. Surface and/or site structure primarily requires spectroscopic characterization, but this is usually accompanied by physi- and chemisorption and model catalytic activity studies. We are currently investigating a variety of catalysts based on mesoporous molecular sieves of the MCM-41 structure. These are synthetic materials with a very uniform hexagonal array of non-intersecting tubular pores. They have the particular advantage that the pore size can be varied systematically in the range of about 1.5-4.5 nm (a range that can be extended to greater than 10 nm) and this is a range where the radius of curvature of the pore wall can affect physical and chemical properties such as the heat of physical adsorption and local bond angles around a site (which may affect the site activity).

In order to investigate the radius of curvature of pore walls on catalytic chemistry, it is first necessary to synthesize materials, which have a constant composition and degree of structural uniformity. Because there are very many synthesis parameters, it is necessary to develop quantitative synthesis models, which we have done for V-MCM-41, Co-MCM-41 and these are being extended to Ni-MCM-41.

We have discovered that we can use the radius of curvature (and other synthesis parameters) and partially reduce isomorphously substituted MCM-41, e.g., Co-MCM-41, to produce very high dispersions of the metal where the metal clusters can be varied in the subnanometer size range. Because Co is a good catalyst for the synthesis of single-wall carbon nanotubes and the diameter of the nanotubes is controlled by the Co cluster size on which the nanotube grows, this provides a method to choose the average diameter of the single-wall carbon nanaotube and to synthesize a very narrow distribution around this average. The single-wall carbon nanotubes are being studied for hydrogen storage and it is observed that the hydrogen storage properties are a function of the diameter of the nanotubes.

Education
B.S. University of Nebraska, Kearney, 1962
Ph.D. Northwestern University, 1966
NATO Postdoctoral Fellow, Oxford University, 1966-67

Honors
Senior Science Council Visiting Fellow, University Edinburg, 1978
Visiting Scholar National Bureau of Standards, 1981

Recent Publications
S. Lim, D. Ciuparu, C. Pak, F. Dobek, Y. Chen, D. Harding, & G. L. Haller. Synthesis and Characterization of Highly Ordered Co-MCM-41 for Production of Aligned Single Walled Carbon Nanotubes (SWNT). J. Phys. Chem. B, 2003, 107, 11048.

Y. Chen, D. Ciuparu, S. Lim, Y. Yang, G. L. Haller, & L Pfefferle. Synthesis of Uniform Diameter Single-wall Carbon Nanotubes in Co-MCM-41: Effects of the Catalyst Prereduction and Nanotube Growth Temperatures. J. Catal. 2004, 225, 453.

S. Lim, D. Ciuparu, Y. Chem, Y. Yang, L. Pfefferle, & G.L. Haller. Pore Curvature Effect on the Stability of Co-MCM-41 and the Formation of Size-Controllable Subnanometer Co Clusters. J. Phys. Chem. B. 2004, 108.

Y. Yang, S. Lim, C. Wang, D. Harding, & G.L. Haller. Multivariate Correlation and Prediction of the Synthesis of Vanadium Substituted Mesoporous Molecular Sieves. Micropor. Mesopor. Mater. 2004, 67, 245.