Development of a corrosion-resistant amorphous silicon carbide photoelectrode for solar-to-hydrogen photovoltaic/photoelectrochemical devices

Photoelectrochemical (PEC) water splitting at a semiconductor-electrolyte interface using sunlight is of considerable interest as it offers a clean approach to hydrogen production. PEC cells require semiconductor photoelectrode materials fulfilling a number of important requirements, such as band-edge alignment, corrosion resistance to electrolyte, and adequate current generation. We report the development of RF-PECVD-deposited hydrogenated amorphous silicon carbide (a-SiC:H) photoelectrodes with improved durability, which, when combined with a-Si:H tandem photovoltaic devices., should produce hydrogen directly from water under sunlight. The a-SIC:H is commonly grown with a bandgap in excess of 2.0 eV and completes the PEC device by providing contact with the electrolyte, proper band-edge alignment, and acts as a buffer for the a-Si:H tandem structure. Effects of the pH of electrolyte, type of substrates, and a platinum nanoparticle coating on the durability of a-SiC photoelectrodes will be presented. From these studies we surmise that corrosion or damage mechanism occurring on a-SiC:H layer could be divided into different aspects of physical and chemical. From the physical point of view, defects associated with spikes in textured TCO substrates, roughness of stainless steel, or other sources of pinholes may initiate delamination as confirmed by SEM (Scanning Electron Microscopy) and EDS (Energy-Dispersive X-ray Spectroscopy) studies. Chemically, the production of hydrogen involves reactions that may etch the electrode, especially when physical defects are involved. We observe that reducing the acidity of the electrolyte (increasing the pH froth 0 to 2) significantly reduces corrosion while the useful photocurrent output of the a-SiC:H p/i structure is unaffected.