(Invited) Structured Electrochemical Materials Fabricated from Directed Self-Assembly of Block Copolymers and Advanced Lithography

Abstract

In this first part of the talk, the process of directed self-assembly will be presented for controlling the microphase separated structure in block copolymer electrolytes (BCEs) with astonishing fidelity. Key results highlight that ionic conductivity of BCEs followed an exponential growth curve with respect to ionic domain connectivity. Conversely, small amounts of terminal defects of the ionic domains rendered no advantage in ionic conductivity for microphase separated systems over non-phase separated systems. Ionic domain alignment to electrode surfaces with a tortuosity of 1 yielded a 4 order of magnitude improvement in ionic conduction over anti-aligned ionic domains. The results suggest that ‘perfect’, long-range ordered structures are necessary for maximizing BCE ionic conductivity. The second part of the talk presents our work on structured electrochemical interfaces for fuel cell and water electrolysis applications. The structured interfaces were prepared by conventional micropatterning and advanced block copolymer lithography. Patterned electrochemical interfaces provide greater interfacial area values that reduce charge-transfer resistances. However, increasing the interfacial area by patterning deeper into electrochemical materials (e.g., into the polymer electrolyte membrane) gave rise to large mass transfer related resistances that eventually offset gains from reduction in charge-transfer resistances. The talk will highlight appropriate design heuristics for fabricating patterned electrochemical interfaces that optimize fuel cell and electrolyzer thermodynamic performance.