Eric R. Choban

Characterization of limiting factors in laminar flow-based membraneless microfuel cells

This paper characterizes the performance-limiting factors of a membraneless microfuel cell in which two aqueous streams flow laminarly in parallel in the absence of a physical membrane without turbulent mixing. The all-liquid configuration allows for easy external addition of a reference electrode, enabling the determination of the type of performance limiting factors such as kinetics and mass transfer limitations, including the source ~anode or cathode!, and the cell resistance. In addition, options to address the present dominating mass transfer limitations at the cathode are discussed.

Membraneless Fuel Cell Based on Laminar Flow

An increasing societal demand for a wide range of small, often portable devices that can operate for an extended period of time without recharging has resulted in a surge of research in micropower sources. Most efforts in this area focus on downscaling of existing fuel cell technology such as the well-known proton exchange membrane (PEM) fuel cells. Here we study a novel concept for fuel cells: the use of laminar flow instead of a physical barrier such as a PEM to separate the fuel and oxidant streams. Laminar flow, i.e. low Reynolds number flow, is a property of fluid flow at the microscale: one or more liquid streams that are brought together under low Reynolds number conditions flow in parallel and contact with each other without turbulent mixing. Mass transport transverse to the direction of flow takes place by diffusion only. In our laminar flow-based fuel cell a fuel-containing stream and an oxidant-containing stream are brought together in laminar flow conditions with the electrodes placed on opposite walls within the channel. In un-optimized fuel cell configurations, current densities as high as 10 mA/cm2 are obtained at room temperature using different fuels such as methanol or formic acid vs. oxygen saturated solvents or other oxidants.© 2003 ASME