Self-assembled mesoporous Ni0.85Se spheres as high performance counter cells of dye-sensitized solar cells

Abstract

Transition metal chalcogenides with mesoporous structure are of special interest for application in electrocatalytic reactions due to their ample unique properties and functionalities. Nevertheless, relevant research on mesoporous Ni_0.85Se applied as electrocatalysts is rare. In this contribution, mesoporous Ni_0.85Se spheres consisting of numerous primary particles are synthesized via a facile self-assembly route. Mesoporous Ni_0.85Se spheres exhibit higher electrocatalytic activity (PCE = 7.24%) for the reduction of triiodide to iodide and lower charge-transfer resistance (R_ct = 2.40 Ω) than Ni_0.85Se nanoparticles (PCE = 6.73%, R_ct = 3.46 Ω) at the electrolyte–electrode interface in dye-sensitized solar cells (DSSCs). In order to further enhance the overall electrocatalytic performance of mesoporous Ni_0.85Se spheres, reduced graphene oxide (RGO) and single wall carbon nanotubes (SWCNTs) are introduced by facile physical mixing. RGO and SWCNT not only improved the charge transfer ability, but also yielded favorable synergistic catalytic effects with mesoporous Ni_0.85Se spheres. Simultaneously, the PCE values of Ni_0.85Se + 6 wt% RGO and Ni_0.85Se + 9 wt% SWCNT reach 7.87% and 7.74%, respectively, which are both higher than Pt (7.56%).