CoSe2/porous carbon shell composites as high-performance catalysts toward tri-iodide reduction in dye-sensitized solar cells

Abstract

Cost-effective, Pt-free catalysts possessing superior electrochemical activity and stability are highly desirable for triiodide reduction reaction in dye-sensitized solar cells (DSCs). Herein, CoSe₂ nanoparticles embedded in porous carbon shells (CoSe₂/CS) were explored as highly efficient catalysts toward triiodide reduction reaction. The CoSe₂/CS composites were fabricated using a soft-template approach involving the carbonization and selenization processes. The CoSe₂ nanoparticles were well distributed within highly graphitized nitrogen-doped carbon nanoshells. More importantly, the CoSe₂/CS catalysts presented both high catalytic performance and long-term stability, outperforming those of the thermally-deposited Pt electrode. Furthermore, the optimized DSC device with a CoSe₂/CS catalyst-based counter electrode showed a power conversion efficiency of 7.54%, exceeding that of the thermally-deposited Pt (7.40%) counterpart. The enhanced catalytic activity, long-term stability and photovoltaic efficiency can be attributed to the much more reaction sites provided by CoSe₂ nanoparticles embedded within the porous carbon shells, as well as the better band matching with the potential of the I₃⁻/I⁻ redox couple, revealed by the Kelvin probe force microscope measurement. This work will provide a strategy to construct low-cost, highly efficient and stable non-Pt catalysts for photovoltaic applications.