Protection of Si photocathode using TiO2 deposited by high power impulse magnetron sputtering for H2 evolution in alkaline media

Abstract

Si is an excellent absorber material for use in photoelectrochemical (PEC) hydrogen production. Only a few studies have been done using Si in alkaline electrolyte for hydrogen evolution due to its poor chemical stability in high pH electrolyte, indicating that a chemically stable protection layer is essential. Here we investigate thin TiO2 films deposited by high power impulse magnetron sputtering (HiPIMS) as a protection layer for a p-type silicon photocathode for photoelectrochemical H2 evolution in a high pH electrolyte. The X-ray reflectometry analysis reveals that the HiPIMS process provides improved film density for TiO2 films (4.15g/cm3), and consequently results in a significantly less corroded Si surface. The Si photocathode protected by the HiPIMS grown TiO2 film along with Pt as co-catalyst produced a photocurrent onset potential of ~0.5V vs. RHE in 1M KOH and showed a 4% decay over 24h in KOH. In contrast, the sample with the TiO2 deposited using conventional DC sputtering technique of similar thickness shows 20% loss in photocurrent for the same time interval. Considering the fact that the experiments were carried out not in the cleanroom, much less corrosion loss can be obtained if done in dust-free condition. Hence, these results suggest the HiPIMS technique as an improved approach for the protection of photoelectrodes, which are unstable in alkaline solution.