Efficient water reduction with gallium phosphide nanowires

Abstract

Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires.

Optical study of the band structure of wurtzite GaP nanowires

“…Furthermore, efficient water reduction in WZ GaP nanowires resulting from an enhanced optical absorption further indicates the direct band gap nature of WZ GaP. 19 However, a detailed study of the optical properties of WZ GaP and a correlation with the predicted band structure is still missing. The electronic band structure calculated for WZ GaP with the density functional theory (DFT) simulating the excitation aspect within the local density approximation (LDA)-1/2 approximation predicts three valence bands for the heavy-hole (C 9v ), light-hole (C 7vþ ), and split-off (C 7v-) bands, as shown in Fig.…”

Conductive-probe atomic force microscopy as a characterization tool for nanowire-based solar cells

“…Semiconductor nanowires (NWs) are promising for photovoltaic applications due to their superior light absorption with respect to their thin film counterparts [1][2][3][4][5][6][7]. The needle-like morphology of NWs is also advantageous for the extraction of the photo-generated carriers via a radial p-n junction design [8,9].…”

Current perspectives in engineering of viable hybrid photocathodes for solar hydrogen generation

“…Roughly, the photocatalytic performance of a hybrid photoelectrode is assayed and compared back-toback with that of a counterpart made solely of the respective light harvester without any catalyst loading. As such, with a catalyst layer, superior catalytic current together with a shifting of the onset potential to more positive value are generally recorded [25]. However, to further improve the system, it is desirable to understand more in mechanistic details of the operation, e.g.…”