Hydrogen Peroxide as an Oxidant for Microfluidic Fuel Cells

We demonstrate a microfluidic fuel cell incorporating hydrogen peroxide oxidant. Hydrogen peroxide (H 2 O 2 ) is available at high concentrations, is highly soluble and exhibits a high standard reduction potential. It also enables fuel cell operation where natural convection of air is limited or anaerobic conditions prevail, as in submersible and space applications. As fuel cell performance critically depends on both electrode and channel architecture, several different prototype cells are developed and results are compared. High-surface area electrodeposited platinum and palladium electrodes are evaluated both ex situ and in situ for the combination of direct H 2 O 2 reduction and oxygen reduction via the decomposition reaction. Oxygen gas bubbles produced at the fuel cell cathode introduce an unsteady two-phase flow component that, if not controlled, can perturb the co-laminar flow interface and reduce fuel cell performance. A grooved channel design is developed here that restricts gas bubble growth and transport to the vicinity of the cathodic active sites, enhancing the rate of oxygen reduction, and limiting crossover effects. The proof-of-concept microfluidic fuel cell produced power densities up to 30 mW cm -2 and a maximum current density of 150 mA cm -2 , when operated on 2 M H 2 O 2 oxidant together with formic acid-based fuel at room temperature.