Thin MoS2 on TiO2 nanotube layers: An efficient co-catalyst/harvesting system for photocatalytic H2 evolution

•A thin layer of MoS2 is site-selectively decorated at the top of anodic anatase TiO2 nanotubes.•Strongly enhanced photocatalytic H2 evolution activity can be observed using 1 nm MoS2 on TiO2 tubes.•The thin MoS2 layer acts as an electron transfer mediator and the TiO2 acts as a light-to-electron harvester.

In the present work, we decorated MoS2 site-selectively at the top of anodic anatase TiO2 nanotubes (TiNTs). For this we sputter-deposited a thin layer (0.5 to 10 nm) of molybdenum onto the tops of the tubes and converted it to sulfide by a thermal treatment in H2S gas. The converted layers were characterized by SEM, XRD and XPS, and tested as an open-circuit photocatalyst for hydrogen evolution. Under AM1.5 (100 mW/cm2) illumination, strongly enhanced H2 evolution activity can be observed using only a nominal 1 nm thick MoS2 decoration on top of a 6 μm thick TiNT layer. We ascribe this strong beneficial effect to two factors: (i) the thin molybdenum sulfide on the top acts as an electron transfer mediator, i.e. as an H2 evolution co-catalyst; and (ii) the underlying tube layer acts as a light-to-electron harvester.