Nanostructured phosphides as photoelectrode materials for artificial photosynthesis

摘要

In this work we describe present experimental results for two related ternary phosphide materials, N-alloyed GaP and ZnGeP_2. These materials represent two potential mid-bandgap photoelectrode materials for artificial photosynthetic systems for solar energy conversion/storage. For photoelectrochemical cells designed to generate energy-rich chemical fuels under illumination, candidate photoelectrode materials should demonstrate the capacity to sustain large photovoltages and photocurrent densities under solar insolation. The results in this work show that the optical properties of these two materials should enable the possibilities for light collection out past 600 nm. For N-alloyed GaP nanowire films, diffuse reflectance spectra show the increase of light absorption at sub-bandgap wavelengths with increasing NH_3(g) used during the annealing step. Corresponding photoelectrochemical data show that the quantum efficiency for light collection at sub-bandgap wavelengths does not follow the same monotonic trend. Separately, we report the first demonstration of ZnGeP_2 nanowire films. The as-prepared materials show reflectance responses consistent with a mid-bandgap material featuring a pseudo-direct bandgap.