Rational integration of hierarchical structural CoS_1.097 nanosheets/reduced graphene oxide nanocomposites with enhanced electrocatalytic performance for triiodide reduction

A novel hierarchical structural hybrid of two-dimensional CoS_1.097 sheets assembled and decorated on reduced graphene oxide sheets (CoS_1.097/RGO) with an intriguing sandwich-like structure are evaluated as electrocatalyst for the reduction of triiodide. In this composite, RGO worked as high speed electronical conductive platforms facilitates transfer of electrons, while CoS_1.097 nanosheets as high-catalytically active centers provide abundant active sites for the reduction of triiodide. In addition, the unique three-dimensional structure can also efficiently accelerate the permeation of electrolyte and thereby elevate the accessibility of inner active sites to redox species. As a consequence, CoS_1.097/RGO exhibits excellent electrocatalytic activity towards triiodide reduction accompanying with a high energy conversion efficiency of 6.85%, which reaches as high as ca. 95.7% to that of Pt CE (7.14%). Furthermore, CoS_1.097/RGO also demonstrates a good long-term stability in I⁻/I₃⁻ electrolyte. The present work provides a rational design strategy to develop the low-cost and high-performance Pt-free alternatives to noble Pt in a DSSC system.