Due to the high energy density of hydrogen it could play an important role as energy storage medium replacing fossil fuels in the future. To produce it in large quantities “artificial leaf”-type structures could be used converting solar light into this fuel by electrochemical decomposition of water. Since this process is most efficient working under acidic conditions in an electrolyzing system semiconducting materials are required on the one hand efficiently absorbing sunlight and generating electron-hole pairs, the energy of which is high enough to split water. To reduce overvoltages on the other hand electro-catalysts are in demand lowering in addition the overvoltages at cathode and anode side.

To replace costly platinum as most efficient HER catalyst for more than a decade attempts were made to replace this noble metal by molybdenum sulfides. It has been shown that nanoparticles of MoS₂ are most efficient consisting of three to four S-Mo-S slabs deposited on a suited support, e.g. MoO_3-x, multiwalled carbon nanotubes (MWCNT) and activated carbon paper [1, 2].

In this contribution, we report on the deposition of (NH₄)₂Mo₃S₁₃ particles on highly fractal MoS₂ layers deposited by reactive magnetron sputtering. Best results were obtained after drop casting a solution of ammonium thiomolybdate on a sputtered MoS₂ film as shown in Figure 1. The modified electrode exhibited an overvoltage of -220mV at a current density of 10mAcm^-2. Since it is known that the edges of the hexagonal MoS₂ crystallites of the sputtered film are containing the highly catalytically active sites this contribution will address the nano-architecture of the modified electrodes.