Template-free synthesis of interconnected carbon nanosheets via cross-linking coupled with annealing for high-efficiency triiodide reduction

Counter electrodes (CEs) play critical roles in the reduction and regeneration of triiodide/iodide redox couple in dye-sensitized solar cells (DSSCs). Compared to commercial Pt, cost-efficient CEs with excellent electrocatalytic activity and superior electrochemical stability are highly desired. Herein, we report a facile, template- and active agents-free fabrication strategy for the synthesis of carbon nanosheets (CNSs) via annealing of small molecular precursors. This process was achieved by a combined strategy, including a low-temperature solid-phase cross-linking reaction and a subsequent high temperature annealing. When employed as metal-free CEs for DSSCs, the as-obtained CNSs demonstrated an annealing temperature-dependent electrochemical behavior. Owing to the superior electrical conductivity and electrocatalytic activity, the CNSs obtained by annealing at 1200 °C exhibit the best electrochemical performance with a power conversion efficiency of 8.71%, which is superior to that of Pt CE (7.24%), thus being attractive alternatives to precious metal Pt CEs. This study presents a simple and effective strategy to configure nanostructured carbonaceous materials for high-performance energy storage and conversion.