Metal-organic framework-derived nitrogen-coordinated cobalt single-atom catalysts for triiodide reduction reaction in solar cells

The counter electrode (CE) is a critical component of a dye-sensitized solar cell (DSSC), and developing Pt-free CEs with high catalytic activities and superior stabilities is urgent. Herein, N-doped carbon-supported Cobalt (Co-NC) single-atom catalysts (SACs) were prepared via in-situ pyrolysis. The DSSCs assembled using the Co-NC SACs CEs exhibited superior power conversion efficiencies (9.25%) compared with those of the DSSCs with the N-doped carbon substrate (6.32%), related Cobalt nanoparticles (7.01%), and Pt (8.05%) CEs. This was attributed to the synergistic effects of the N-doped C matrix and single dispersed Co species, which could provide high active Co–Nx as well as a porous structure that offered unobstructed access to the electroactive sites. The catalytic mechanism was elucidated from I3- and I adsorption, I2 and I- dissociation and charge transfer process by DFT calculations. This study expands the range of non-noble metal CE materials for the commercialization of DSSCs.