Data presented in figures in the article titled: Dodecagonal GaN Microrods: Chemical Stability of a-, m-, and c-Plane Walls and Their Application to Water-Splitting, citation: Adv. Mater. Interfaces 2024, 11, 2400392, https://doi.org/10.1002%2Fadmi.202400392
Figure 1. The schematic structure of a working electrode (a) and its SEM image (b). Gallium droplets were removed by HCl etching before In contacts aremade. Inset in (b) shows individual rods with bare rod tops and plane orientations indicated for sidewalls (a-plane indicated in yellow, m-plane indicatedin red) and microrod top (c-plane indicated in blue). In panel (c) a similar as-grown structure with microrods grown for 2.5 h is shown highlighting thescalability of the process. Inset in (c) shows individual rods with the Ga droplet on top.
Figure 2. A schematic of the formation of (a) solid and (b) hollow coreGaN microrods. The formation of Ga droplet over a v-pit results in subse-quent growth with a hollow core. Insets in (a) and (b) show examples ofsolid and hollow core microrods.
Figure 3. a) The photoelectrolysis setup consisting of a quartz container filled with an electrolyte. Three electrodes are submerged: a microrod GaNworking electrode, an Ag/AgCl reference electrode, and a Pt counter electrode. Light is provided by a solar simulator lamp. b) I–V characteristics of thereference planar water-splitting structure measured in 1 mol dm−3 NaOH electrolytic solution.
Figure 4. I–V characteristics of two microrod water-splitting structures measured in a basic solution. Structures were grown at a) 670 and b) 700 °Csubstrate temperature. In dark there is no current without supplied bias. At ≈1.2 V an increase is observed which corresponds to the electrochemicalpotential of water (1.23 V). Under illumination, a significant current is observed at zero supplied bias.
Figure 5. SEM images of a) planar and b,c) microrod structures after 5 h of the photoelectrolysis process. Visible is the damage due to chemical etchingin all three images. In the inset of panel (c) remains of a microrod are magnified showing roughening of the sidewall with the top mostly intact.
Figure 6. SEM images of individual microrods a,b) before and after water-splitting processes in NaOH for c,d) 10, (e,f) 20 min, and g,h) 30 min. Anincreasing level of degradation of sidewalls is visible with increasing exposure time.
Figure 7. HAADF-STEM characterization; a) STEM image of an as-grown rod cross-section. In panel (b) and (c) m- and a-plane sidewalls are shownmagnified, respectively. HR-STEM images confirming the orientation of the sidewalls are shown in panels (d) and (e) for m- and a-plane sidewalls,respectively. For better readability m-plane related features are marked with red lines and a-plane with yellow lines.
Figure 8. HAADF-STEM characterization; a) STEM image of a post water-splitting process rod cross-section. In panel (b) and (c) m- and a-planesidewalls are shown magnified, respectively. HR-STEM images confirming the orientation of the sidewalls are shown in panels (d) and (e) for m- anda-plane sidewalls, respectively. For better readability m-plane related features are marked with red lines and a-plane with yellow lines.
Figure 9. Ga L3 XANES spectra of a) the GaN epilayer and as-grown microrods and b) as-grown and NaOH treated GaN microrods.
SEM images aquired on a Thermo Fisher Scientific HELIOS Nanolab 450 HP system.
TEM/STEM images aquired on a FEI TITAN Cubed 60-300 system.
I-V characteristics measured using a Keithley 2450 SourceMeter source measure unit and processed in OriginPro.
X-ray Absorption Spectroscopy XANES spectra were collected at the SOLARIS National Synchrotron Radiation Centre, Krakow, Poland and processed in OriginPro.
(2024-09-24)
