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Precise control of electron density at catalyst active sites enables regulation of surface chemistry for the optimal rate and selectivity to products. Here, an ultrathin catalytic film of amorphous alumina (4 nm) was integrated into a catalytic condenser device that enabled tunable electron depletion from the alumina active layer and correspondingly stronger Lewis acidity. The catalytic condenser had the following structure: amorphous alumina/graphene/HfO2dielectric (70 nm)/p-type Si. Application of positive voltages up to +3 V between graphene and the p-type Si resulted in electrons flowing out of the alumina; positive charge accumulated in the catalyst. Temperature-programmed surface reaction of thermocatalytic isopropanol (IPA) dehydration to propene on the charged alumina surface revealed a shift in the propene formation peak temperature of up to ΔTpeak∼50 °C relative to the uncharged film, consistent with a 16 kJ mol-1(0.17 eV) reduction in the apparent activation energy. Electrical characterization of the thin amorphous alumina film by ultraviolet photoelectron spectroscopy and scanning tunneling microscopy indicates that the film is a defective semiconductor with an appreciable density of in-gap electronic states. Density functional theory calculations of IPA binding on the pentacoordinate aluminum active sites indicate significant binding energy changes (ΔBE) up to 60 kJ mol-1(0.62 eV) for 0.125 e-depletion per active site, supporting the experimental findings. Overall, the results indicate that continuous and fast electronic control of thermocatalysis can be achieved with the catalytic condenser device.
Bibliographical noteFunding Information:
We acknowledge financial support from the U.S. Department of Energy, Basic Energy Sciences Catalysis program (DE-SC0021163) and the National Science Foundation CBET-Catalysis program (award #1937641). S.R.G. was supported by the National Science Foundation Graduate Research Fellowship under Grant CON-75851, project 00074041. S.G. and K.A.M. were supported by University of Minnesota (UMN) MRSEC program DMR-2011401. The electron microscopy work was carried out in the Characterization Facility of University of Minnesota supported in part by the NSF through the UMN MRSEC. We thank Keith and Amy Steva for their generous support of this project through their donor advised fund. We thank Professor Aditya Bhan for helpful conversations.
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- catalytic condenser
PubMed: MeSH publication types
- Journal Article
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- 2 Active
9/1/20 → 8/31/26
Project: Research project