PHOTOELECTROCHEMICAL SYSTEMS FOR HYDROGEN PRODUCTION

Abstract

Two important research areas that are part of NREL’s effort towards a photoelectrochemicalbased (PEC) direct water splitting system include surface modification to improve system energetics and triple junction amorphous silicon structures (α-Si) as a low-cost thin-film water spitting system. In the area of surface modification, p-GaInP2 surfaces were tailored by adsorption of metallated porphyrins and transition metals with the aim of moving band edge energies as well as catalyzing interfacial charge transfer for photoelectrochemical hydrogen generation. Mott-Schottky analyses in pH 4 buffer showed that adsorption of RuOEP CO with either RuCl3 or platinum sol shifted band edges in a positive direction by 0.48 V which is sufficient to allow the overlap of the bandedges with the water redox potentials in the dark. Charge transfer analysis showed that adsorption of RuOEP CO with RuCl3, catalyzes charge transfer for the p-GaInP2 surface up to a photocurrent of 1 mA/cm 2 . However, despite these surface modifications, two-electrode I-V curves show no improvement over unmodified systems. In the area of an α-Si-based system the work involved the characterization of various α-Si triple junction structures, and a study on the ability of α-SiC to protect the surface from corrosion. Samples underwent current-voltage tests, corrosion measurements, and metal-ion catalyst treatments. The α-SiC samples were tested for their characteristics relating to their effect on the overall efficiency of water splitting, and the ability of α-SiC for protecting the underlying semiconducting material.