(745b) Two-Cell Photoelectrochemical Water Splitting Prototype Demonstration System

Hydrogen generation by photoelectrochemical (PEC) water splitting is a promising technology for solar energy storage. However, large scale application of PEC systems in their current single-cell design is technically challenging and economically questionable since the hydrogen is produced at the solar site. Accordingly, a PEC hydrogen production plant requires hermetic sealing of the entire solar array, construction and maintenance of an immense hydrogen piping infrastructure, and constant sensing for hazardous leaks. In our previous paper[1], published in 2017 in Nature Materials, we presented our solution to these issues by separating the hydrogen and oxygen cells using solid-state redox mediators based on nickel hydroxide. This allows for the oxygen-generating PEC cell to remain completely open, eliminating the need to hermetically seal the solar site, fit it with membranes and collect the hydrogen from that site. The hydrogen is then generated in a separate, compact electrochemical cell directly at the end-user's location. Thus far, a few PEC cell designs have been proposed based on the single-cell configuration. In this work, we present a first of its kind prototype of a two-cell PEC device based on a 100 cm² hematite photoanode stack and commercial Si PV modules. Battery-grade nickel hydroxide electrodes are used as redox mediators between the cells. This prototype device has been designed and optimized for continuous PEC hydrogen production. The issues of material selection, stability, light harvesting and operation scheme are addressed and discussed.

[1] Landman, A., Dotan, H., Shter. G. E., Wullenkord, M., Houaijia, A., Maljusch, A., Grader, G., and Rotschild, A. (2017). Photoelectrochemical water splitting in separate oxygen and hydrogen cells. Nature Materials, March, 1-7.