Fig. 1. (Color online) Schematic diagram showing the two-step preparation of 4H-SiC nanoporous arrays. The effect of each etching step is displayed in the figure.

Fig. 2. SEM images of the surface morphologies of (a) original 4H-SiC, (b) S2, (c) S5, (d) S10, (e) S20, and (f) S30. (g) and (h) are cross-sectional SEM images of S10 at low and high magnifications, respectively.

Fig. 3. (Color online) (a) Raman spectra and (b) optical absorption curves of S2, S5, S10, S20, S30, and original 4H-SiC.

Fig. 4. (Color online) (a) LSV and (b) EIS of S2, S5, S10, S20, S30, and original 4H-SiC under simulated sunlight illumination. The inset is the Randles equivalent circuit fitting diagram. (c) Current−time (I−t) curves of the S10 at 1.23 V vs RHE. (d)−(f) Schematic diagram showing the effect of the thickness of the walls of 4H-SiC nanoporous arrays on the carrier transport during PEC water splitting.

Fig. 5. (Color online) (a) The LSV curves of the different-dose electron-irradiated 4H-SiC nanoporous arrays under simulated sunlight illumination at 1.23 V vs RHE. (b) I−t curves of 4H-SiC nanoporous arrays under simulated sunlight illumination before and after different-dose electron irradiation.