Facile synthesis of Co_0.85Se nanotubes/reduced graphene oxide nanocomposite as Pt-free counter electrode with enhanced electrocatalytic performance in dye-sensitized solar cells

A novel nanocomposite of Co_0.85Se nanotubes with reduced graphene oxide (Co_0.85Se/RGO) is prepared by a facile hydrothermal approach coupled with in situ selenization, which is applied as counter electrode in dye-sensitized solar cells. Electrochemical analysis shows that the Co_0.85Se/RGO composite displays a higher electrocatalytic activity for the reduction of triiodide respect to its single components due to the unique hollow structure of Co_0.85Se as well as the synergistic effects of high catalytically active Co_0.85Se and conductive RGO. As a consequence, the dye-sensitized solar cell (DSSC) fabricated with the Co_0.85Se/RGO electrode presents a high photovoltaic conversion efficiency of 7.81%, exceeding the cell based on a Pt electrode (7.55%). Moreover, a considerable electrochemical stability is also achieved when the material was used as a counter electrode in a I⁻/I₃⁻ electrolyte. Therefore, the Co_0.85Se/RGO exhibits a huge potential as efficient and low-cost Pt-free counter electrode material to replace Pt allowing for large-scale fabrication of DSSCs.