The role of surface-wettability in electrochemical reactions involving gas-phase reactants or products.

by Mehrabi, Hamed; Coridan, Robert

Electrolytic reactions like water splitting or CO2 redn. are attractive as chem. fuels generated by renewable electricity. The gas-liq.-solid phase boundary often plays a significant role in the energy conversion efficiency of these reactions. In water splitting, evolving hydrogen and oxygen bubbles block large regions of active area, increasing the overpotential required to maintain the same rate of reaction. For the electrochem. redn. of CO2, the insoly. of CO2 reactants limits the achievable Faradaic yield of the desirable hydrocarbon products, shifting most of the electrochem. activity towards hydrogen evolution with the aq. electroyte. Here, we explore strategies for the favorable control of the gas-liq.-solid phase boundary through hierarchically-structured superhydrophobic coatings on electrocatalytic substrates. By engineering the organization of superhydrophobic and electrolytically active areas on electrodes, we can understand how to preserve the interface, promote reactions by increasing the effective concn. of reactants at the electrolytic sites, or clear active areas by stimulating bubble nucleation at other parts of the electrode. We will describe our exptl. efforts to study the nature of these electrodes through both precisely defined, lithog. patterned surface structures and scalable, self-assembled coatings based on nano- and microstructured hydrophobic polymers on thin-film metal electrodes. We will also illustrate potential applications of these surfaces for aq.-phase electrochem. reactions.