Porous carbon dodecahedra containing cobalt nanoparticles as the electrocatalytic counter electrodes for dye-sensitized solar cells

The cobalt nanoparticles (10 nm) were homogeneously embedded in the porous carbon dodecahedra (about 1 mu m in size) through thermal pyrolysis of the ZIF-67 (zeolitic imidazolate framework-67) dodecahedra under an inert atmosphere. The pore sizes of the carbon dodecahedra were found to disperse in three ranges of micropores, small, and large mesopores. Cyclic voltammetry measurements indicated that the porous carbon-cobalt electrode with small particle size (SPC-Co) exhibited better electrocatalytic performance than that with large particle size (LPC-Co), primarily owing to its larger electrocatalytic surface for boosting the redox reaction between iodide and triiodide ions. Dye-sensitized solar cell (DSSC) using the SPC-Co counter electrode (CE) showed a superior photovoltaic conversion efficiency of 10.6%, which was better than those achieved by means of Pt (9.8%) and LPC-Co (9.0%) CEs. The improved photovoltaic behavior of DSSC employing the SPC-Co CE could be attributed to its lower internal resistance than the other CEs. The porous carbon rhombic dodecahedra with embedded cobalt nanoparticles could achieve fast kinetics and high electroactivity in catalyzing the iodide/triiodide redox couple. (C) 2018 Elsevier B.V. All rights reserved.