An Efficient Photoelectrochemical Hydrogen Evolution System using Silicon Nanomaterials with Ultra‐High Aspect Ratios

We fabricated ultra‐high aspect ratio silicon nanomaterials, including a silicon nanomesh and silicon nanowire array, on a wafer scale for efficient photoelectrochemical hydrogen production. These silicon nanomaterials (feature size≈20 nm) possess a high aspect ratio to increase the optical absorptivity of the cells to approximately 95 % over a broad range of wavelengths. The silicon nanomesh and Si nanowire cells achieved high photocurrent values of 13 and 28 mA cm −2 , respectively, which are increased by 200 % and 570 % in comparison to their bulk counterparts. In addition, these scalable Si nanomaterials remained stable for up to 100 min of hydrogen evolution. Detailed studies on the doping and geometrical structures of the resulting hydrogen evolution cells suggest that both the n + pp + doping and thickness of nanostructures are keys to the enhancement of the hydrogen evolution efficiency. The results obtained in this work show that these silicon nanomaterials can be used for high‐performance water‐splitting system applications. The straight doping: Wafer‐scale ultra‐high aspect ratio Si nanomesh/nanowires (feature size≈20 nm) were fabricated and utilized to produce an efficient photoelectrochemical hydrogen evolution system. The Si nanomesh cell yielded extreme optical absorptivity, high external quantum efficiency, and high photocurrent. Detailed studies suggest that both the n + pp + doping and thickness of nanostructures are keys to the enhancement of the hydrogen evolution efficiency.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109595/1/ente_201402074_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109595/2/889_ftp.pd