III–V core / oxide shell nanowires for light–driven water splitting
Abstract
Photoelectrochemical cells (PEC) are one of the most promising approaches for the production of alternative energy carrier in the global effort to diminish the usage of fossil fuels [1]. In this context, III-V nanowires (NWs) based photoelectrodes [2, 3] are particularly attractive thanks to their high surface/volume ratio, efficient charge separation and collection and their light trapping potential. However, III-V NWs suffer from corrosion in aqueous electrolyte, which prevents their utilization for a long period. In order to avoid the surface degradation of the NWs under working conditions, a particular attention has to be given to their surfaces. We proposed to grow an oxide shell, transparent to visible light and compatible with the carrier transfer from the III-V semiconductor to the electrolyte, to increase the viability of these photoelectrodes.
GaAs NWs were grown by molecular beam epitaxy (MBE) using the vapor-liquid-solid (VLS) mechanism on silicon substrate [4, 5], and a TiO2 shell was deposited by atomic layer deposition (ALD). The morphology, and interface of the NWs were studied by scanning transmission electron microscopy and electron energy-loss spectroscopy. Measurements performed on the PEC revealed an enhancement of the photoactivity by a factor 20 comparing a thin layer of GaAs and optimized GaAs NWs, reaching a current density of around 1.2 mA/cm² at 0.0 V vs RHE [6].
[1] N. Armaroli et al, Angew. Chem. 46, (2007), 52
[2] M. G. Kibria et al, Nat. Commun. 5 (2014), 3825
[3] N. Kornienko et al, ACS Nano 10 (2016), 5525
[4] T. Dursap, et al, Nanoscale Adv., 2, (2020), 2127-2134
[5] T. Dursap, et al, Nanotechnology, 32, (2021), 155602
[7] This work was done as part of the ANR BEEP project (ANR-18-CE05-0017)
Origin : Files produced by the author(s)