Sunday, February 19, 2017
Exhibit Hall (Hynes Convention Center)
Jacqueline Ohmura, MIT, Cambridge, MA
Electrocataysts provide enormous potential in providing clean energy and enabling sustainable fabrication processes. Before these goals can be achieved on a wide scale, electrocatalytic processes must exhibit high faradaic efficiencies and energetic efficiencies at reasonable current densities. Despite the importance of both electrocatalyst composition and structure to catalyst performance, few studies to date have focused on the effects of electrode structure or the synergy between composition and structure on electrocatalyst performance. To enable such analyses, we developed a facile synthesis method enabling nano-scale structural control independent of composition. This study details the ability of the M13 phage to serve as a synthetic functional handle to simultaneously tune nano-scale structure and composition independently. Hydrogels of M13 virons were formed via addition of the crosslinking agent, glutaraldehyde. These hydrogels displayed adhesion to several substrates including silicon, silica, metal foams, and glass enabling the synthesis of nanonetworks onto a variety of structures. Next, the coat protein of the M13 viron was genetically modified to express three glutamic acid residues at the exposed terminus of the protein. These negatively charged residues contributed to an electrostatic interaction between the viron and positively charged sensitizing agent enabling subsequent electroless deposition of transition metals onto phage based hydrogels. A wide range of compositional and structural variations of M13 based nanonetworks was subsequently synthesized and characterized. Synthetic control over nanowire thickness was accomplished from 50-200nm. With respect to composition, separate nanonetworks of copper, cobalt, and nickel were successfully fabricated and confirmed via TEM, XRD, and EDS. Each of these materials were further modified via a second deposition of copper, nickel, gold, or zinc oxide to produce alloys and/or composites on a continuum of ratios. Incorporation of the second material of up to 100 wt% was achieved, thus enabling synthesis of all possible ratios in these two material systems. Through additional biological modifications, nanonetwok structure was further altered. M13 coat incorporation of amino acids with large sterically hindering chemical groups introduced global changes in nanonetwork pore shape, while the introduction of DNA templates produced brush like structures onto the nanonetwork surface. It is anticipated that this synthesis method will enable the optimization of electrocatalyst performance for reactions such as CO2 reduction and alcohol oxidation both of which directly reduce unwanted byproducts of energy production and generate low-carbon fuels or desired chemicals in the process.