Composition-Dependent Electrocatalytic Activity of Cobalt Sulfides for Triiodide Reduction in Dye-Sensitized Solar Cells

Abstract

A new nanoarchitecture of cobalt sulfide (CoSx) is designed by exploiting a Prussian blue analogue. Depending on the sulfidation temperatures, CoSx materials with different compositions and morphologies are obtained. This investigation of the composition-dependent electro-catalytic activity of CoSx for triiodide reduction reaction (IRR) reveals that sulfur-deficient CoSx is more active than sulfur-rich CoSx. When utilized in dye-sensitized solar cells (DSSCs), sulfur-deficient CoSx with a hollow nanocube morphology outperforms platinum (Pt), showing great promise as a Pt alternative. This composition dependency on IRR is attributed to different surface characteristics and electrical properties that vary with CoSx composition. This work highlights the importance of understanding the surface properties of sulfide-based electrocatalysts that are intimately dictated by their compositions as part of a new design principle for a highly active electrocatalyst.