Architecture for a low-overpotential, gas-separated photoelectrolysis system

Abstract

We are taking a modular, parallel approach to the development of an artificial photosynthetic system that will utilize sunlight and water to produce hydrogen and oxygen. The three distinct components-the photoanode, the photocathode, and the productsepg. but ion conducting membrane-are fabricated sep. before assembly into a complete water-splitting system. The photoanode and photocathode will consist of rod-like semiconductor components, with attached heterogeneous multi-electron transfer catalysts, which are needed to drive the oxidn. or redn. reactions at low overpotentials. Optimized mass transport of reactants and products, light absorption, and carrier collection in this system requires for these components to be engineered on length scales from a few nanometers up to millimeters. The high aspect-ratio rod electrode architecture allows us to produce these semiconductors using low cost methods and earth abundant materials without sacrificing energy conversion efficiency due to the orthogonalization of light absorption and charge-carrier collection. Addnl., the high surface-area design of the structured semiconductor electrode inherently lowers the flux of charge carriers over the rod array surface relative to the projected geometric surface of the photoelectrode. This lowers the photocurrent d. at the solid/liq. junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. A flexible composite polymer film will allow for the sepn. of gaseous products while simultaneously permitting electron and ion conduction between the photoanode and photocathode and providing structural support. Sep. polymeric materials will be used to make elec. contact between the anode and cathode and to form interspersed ion conducting patches to maintain charge balance between the two half-cells.