438658 Rational Catalyst Design for Renewable Energy Technologies

Sunday, November 8, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Samira Siahrostami, SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford, CA

Today two of the most prominent issues, associated with a growing world population and increased standards of living, are climate change caused by CO2 emissions and the availability of clean drinking water. There is general interest in replacing fossil fuels to supply mankind energy needs sustainably on a long-term basis. Ideally this is done by 1) producing energy using alternatives such as fuel cells, electrolyzers or batteries, 2) synthesizing fuels using biomass, methane oxidation or electrochemical conversion of CO2to hydrocarbons. Heterogeneous catalysis is at the heart of all these renewable energy technologies.

There are, however, severe shortcomings of the present technologies, which need to be overcome to make these processes more economically attractive. One of the most important problems is the lack of active, selective and inexpensive catalysts for these processes. Any progress in this field is connected to the concept of scaling relations[1], which is the correlation between surface bond energies of different adsorbed species for specific reaction. The scaling relations pose limitations on many of the known catalysts for reactions such as oxygen reduction (ORR), oxygen evolution (OER), CO2 reduction and N2 reduction reactions.[2] Therefore, catalyst design requires development of new, effective and non-precious catalysts with active site motifs, which obey different scaling relations than the so far recognized ones. My work utilizes theoretical tools in particular density functional theory (DFT) to model graphene, boron-nitride and oxide materials with different modifications strategies including doping and defect design to describe the surface reactions. These strategies have not been explored so far. I seek to find a breakthrough for scaling relations and my goal is to discover novel catalysts for the following applications: 1) improving the efficiency of the devices that are related to sustainable energy applications, i.e. fuel cells[3], electrolyzers[4], and metal-air batteries[5], and 2) to discover/design new, effective and non-precious catalysts for ORR, OER, CO2 and N2 electrochemical reduction reactions, fuel synthesis from biomass, and methane oxidation.

Another important issue facing humanity is related to the potable water. Millions of people in the developing world are lacking access to drinking water due to its contamination with urban, industrial and agricultural waste. These pollutants can in principle be removed by their total oxidation by hydrogen peroxide (H2O2) as a strong oxidizing agent without leaving any residues behind. Production and transportation of H2O2 to the developing world, however, is challenging due to high costs and safety issues, making this potentially game-changing chemical largely inaccessible to the massive number of people who need it the most. My research combines the expertise from fundamental understanding of the reaction and DFT with versatile synthetic methods, electrochemical evaluation and catalyst characterization to develop an electrochemical route by designing an efficient and cost effective electrocatalyst for selectively reducing O2 to H2O2 to enable continuous, small-scale and decentralized production of H2O2 with minimal danger of explosion.[6,7] 

[1] Abild-Pedersen, F., Greeley, J.P. and Studt, F. et al. Phys. Rev. Lett., 99, 2007, 016105.

[2] Vojvodic, A., Nørskov, J.K., National Sci. Rev., 2, 2015, 140.

[3] Siahrostami, S., Bjorketun, M.E.  et al. Phys. Chem. Chem. Phys. 15, 2013, 9326.

[4] Siahrostami, S., Vojvodic, A., J. Phys. Chem. C, , 2015, 119, 1032.

[5] Siahrostami, S., Tripkovic, V., et al. Phys. Chem. Chem. Phys. 15, 2013, 6416.

[6] Siahrostami, S., Verdaguer-Casadevall, A., et al. Nat. Mater. 12, 2013, 1137.

[7] Verdaguer-Casadevall, A., Deiana, D.,  Karamad, M., Siahrostami, S., et al. Nano Lett. 14, 2014, 1603.

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