Electrochemical properties and long-term stability of molybdenum disulfide and platinum counter electrodes for solar cells: A comparative study

The electrocatalytic properties of few-layer thick MoS2 films, grown on Mo foils by soft sulfurization, are explored in two different redox shuttles, i.e. S2-/S-n(2-) and I-/I-3(-). The dependence of the MoS2 catalytic activity on cycling in the polysulfide electrolyte is explored for the first time. MoS2 exhibits an unprecedented self-improving behavior with increasing cycling, in addition to extraordinary stability against corrosion under soaking conditions for up to two months. On the contrary, Pt-based nanostructured catalysts present appreciable deactivation under the same conditions. Pristine and pretreated MoS2 films in a polysulfide electrolyte under successive cycling are evaluated as counter electrodes in DSSCs and the effect of the number of cycles is examined. The DSSC with the pretreated MoS2/Mo foil CE yields a 35% and a 20% increment of the efficiency and the short circuit current density respectively, compared to an untreated CE. Besides, the role of the surface roughness of Mo foil in the catalytic activity and stability of the MoS2 films has been examined. The current results show that tailoring the morphology of nanometer- thick MoS2 films - grown by sulfurization of Mo foils - can lead to enhanced electrocatalytic properties compared to Pt-based nanostructured films. (C) 2018 Elsevier Ltd. All rights reserved.