Vertically-aligned sandwich nanowires enhance the photoelectrochemical reduction of hydrogen peroxide: hierarchical formation on carbon nanotubes of cadmium sulfide quantum dots and Prussian blue nanocoatings.

•Arrays of sandwich nanowires consist of CdS and Prussian blue on carbon nanotubes.•Electrons flow into Prussian blue from CdS upon light radiation.•The nanowires’ alignment ensures optimal pathways transferring mass and electrons.•The photoelectrocatalytic reduction of H2O2 enables high output in fuel cells.