annealing method. The classic problem is that when annealed in air at> 500° C, the
individual particle size increases from≈ 20 nm to 40–60 nm. This grain growth is highly
detrimental for the water splitting efficiency. In the present work we show that grain
coarsening can efficiently be prevented by a two-step annealing method in Ar, leading to
photocurrent densities for such electrodes (obtained in 1 M KOH solution) of up to 2.6 mA …