(Invited) Development of Bimetallic Electrocatalysts and Electrodes for Carbon Dioxide Electrolysis Via Direct Deposition Strategies

The development of energy efficient carbon dioxide (CO₂) electroreduction processes would simultaneously curb anthropogenic CO₂ emissions and provide suistainable pathways for fuel generation.  If such electroreactors employed CO₂ feedstocks from major emission sources (e.g., thermal power plants) and excess electricity from intermittent locally-available renewable resources (e.g., solar, wind), then chemicals of economic value could be generated in a carbon neutral fashion [1].  While significant efforts have been focused on heterogeneous CO₂ electroreduction to various products including carbon monoxide (CO), formic acid, and methanol; to date, no process has been able to demonstrate both high energetic efficiencies and high current densities [2].  A key challenge in the development of active, selective, and stable electrocatalysts is translating performance nanomaterials to appropriate electrodes which augment catalyst activity by maximizing surface area, facilitate species transfer, and minimize undesirable side reactions [3,4].

Direct deposition (e.g., electrodeposition, galvanic replacement) of nanostructured electrocatalysts onto microporous metal foam electrodes may offer a pathway to high performance electrodes.  Metal foams hold two key advantages: (i) their porous nature facilitates extended tunable electrochemical interfaces without sacrificing transport of reactants and ions; and (ii) they can act as a conductive substrates for the direct deposition of active materials eliminating the need for conductive additives and binders [5].  Further, as many active metals can form foams, surface alloys and multi-metallics could be created through deposition and annealing.  This talk will focus the development of Au/Cu and Ag/Cu core/shell catalysts via galvanic replacement reactions.  First, we will discuss the synthesis, characterization, and performance evaluation of Cu nanoparticles / nanowires with a few Au or Ag monolayers.  We will then describe the translation of these active materials to microporous Cu foam electrodes, subjected to various electrochemical pretreatments, which, in turn, will be evaluated in small-scale flow cells.

Acknowledgements

We gratefully acknowledge the financial support from the MIT Center for Materials Science and Engineering.

References

[1] D.T. Whipple, P.J.A. Kenis, J. Phys. Chem. Lett., 2010, 1, 3451-3458

[2] A.M. Appel et al., Chem. Rev., 2013, 113, 6621-6658

[3] H.R.M. Jhong, F.R. Brushett, P.J.A. Kenis, Adv. Energy Mater., 2013, 3, 589-599

[4] J. Wu, F.G. Risalvato, P.P. Sharma, P.J. Pellechia, F.-S. Ke, X.-D. Zhou, J. Electrochem. Soc., 2013, 160, F953-F957

[5] Y. Li, Z.-Y. Fu, B.-L. Su, Adv. Funct. Mater., 2012, 22, 4634-4667