Michael R. Hoffmann
The Linde Center for Global Environmental Science
California Institute of Technology
Lecture: 3 p.m. — Brauer Hall, Room 12
Reception: to follow — Brauer Hall, 1st Floor Lobby
Talk Title — “Electrochemical Oxygen & Chlorine Production: Enhancing Electrocatalytic Activity Using Atomic Layer Deposition"
Abstract: The economical generation of fuels and commodity chemicals from renewable electricity sources depends on the development of highly active electrocatalyst. Despite their advantages (e.g., facile product separation), the industrial use of heterogeneous electrocatalysts is still limited by current catalyst efficiency and selectivity. While many methods and design tools such as doping, strain induction, mixing metal oxides and others exist to improve the catalytic activity of heterogeneous electrocatalysts. However, the conventional methods are either limited by specific material parameters or by the ability to predict specific catalytic activity resulting from alteration of catalyst properties (e.g., doping). Thus, finding new tools to tune the intrinsic activity of catalysts represents a continuing challenge in the field of heterogeneous electrocatalysis. In our case, Atomic layer deposition (ALD) provides an attractive method for tuning electrocatalysts by precisely altering their surface charge densities. We applied TiO2 via ALD to tune three heterogeneous electrocatalysts (IrO2, RuO2, and FTO) for the oxygen and chlorine evolution reactions (OER and CER). The electrocatalysts with ~3-30 ALD cycles of TiO2 had measured overpotentials at 10 mA/cm2 that were several hundred mVs lower than the uncoated, naked catalyst surfaces. In addition, controlled deposition of TiO2 resulted in higher OER specific activities in 1 M H2SO4 (0.87 mA/cm2ECSA at 350 mV η) than previously reported in the literature. The oxidation state of titanium and the potential of zero charge (EPZC) were also shown to sensitive to the number of successive ALD cycles. These results suggest that with a controlled number of ALD cycles ≤ 30 the catalytic activity of electrocatalysts can be enhanced and at the same time protected against erosion and inactivation. Additional advances using Cobalt-doped Black TiO2 nanotube electrodes will be presented.
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