Controllable (Ga1−xZnx)(N1−xOx) nanorods grown on black silicon as anodes for water splitting

Abstract (Ga1−xZnx)(N1−xOx) has attracted extensive attention in photoelectrochemical (PEC) water splitting for its narrow and controllable band gap recently. For optimizing PEC performance of (Ga1−xZnx)(N1−xOx) photoanodes, the key points are to tailor its band gap and improve the light harvesting. In this work, black silicon prepared by metal-assisted chemical etching (MACE) is selected as the substrate of photoanodes, owing to its excellent features such as porous structure and much lower reflective index compared to smooth Si wafer. Moreover, a rapid and effective synthesis method is developed to prepare (Ga1−xZnx)(N1−xOx) nanorods with ZnO content from 16 to 94% on black silicon. As prepared black silicon/(Ga1−xZnx)(N1−xOx) nanorods were characterized by XRD, FESEM, EDS, XPS, TEM and UV–Vis et al. The (Ga1−xZnx)(N1−xOx) nanorods with a diameter of 200 nm and an aspect ratio of 15 are directly grown on black silicon as photoanodes, which lead to much better light harvesting and better interface adherence. As a consequence, the photocurrent density of black silicon/(Ga1−xZnx)(N1−xOx) nanorods photoanode is 55 μA/cm2, almost 5.5 times higher than (Ga1−xZnx)(N1−xOx) nanorods on single-crystal silicon under the same conditions. The result indicates that the (Ga1−xZnx)(N1−xOx) nanorods grown on black silicon as photoanodes have great potential application in the PEC water splitting.