Improved photo-stability of silicon nanobelt arrays by atomic layer deposition for efficient photocatalytic hydrogen evolution

Abstract Silicon nanostructures have recently drawn great interest for use as photocathodes to produce hydrogen through water photoelectrolysis. Despite the high photocurrent observed, nanostructured Si photocathodes usually exhibit poor photo-stability in aqueous solution and rapidly deactivate. Herein, we report that by coating a thin titania protection layer using atomic layer deposition (ALD), the photo-stability of silicon nanobelt arrays fabricated by metal assisted chemical etching can be markedly improved. The photocurrent loss of the silicon nanobelt array photoelectrode coated with a 3 nm titania layer is found to be much lower than that of the electrode without a titania coating. We also demonstrate that the 3 nm titania coated Si nanobelt arrays can sustain more than twelve hours without a significant loss in photocurrent under operation conditions before it eventually fails. The possible failure mechanism is preliminarily investigated.