Chemically grafting graphene oxide to B,N co-doped graphene via ionic liquid and their superior performance for triiodide reduction

Abstract

The fast reduction and regeneration of triiodide/iodide (I3−/I−) redox couple is one of the key issues for low cost dye-sensitized solar cells (DSSCs). Compared with traditional and expensive Pt counter electrodes (CEs) that act as the catalyst for reduction and regeneration of I3−/I−, the low-cost and high-efficiency CEs are highly sought after for Pt replacement. Here, we report an efficient strategy for synthesis of B and N co-doped graphene (B,N-G) samples via chemically grafting ionic liquid (IL), followed by thermal annealing. The corresponding photovoltaic and electrochemical performances were investigated in detail. It was found that chemically grafting via IL is an efficient strategy for inhibiting and avoiding the agglomeration and restacking of graphene oxide (GO) sheets to a great degree in comparison to that of physically mixed IL and GO, further leading to efficient doping. When evaluated as CEs for DSSCs, an annealing temperature-dependent electrochemical behavior is demonstrated in B,N-G samples. The B,N-G-1200 annealed at 1200°C derived from IL-grafted GO as CE has demonstrated the best electrochemical performance, yielding a power conversion efficiency of 8.08% the synergetic effects of co-doped B and N, which is superior to 6.34% of Pt CE. The present work will provide a simple and efficient method for configuring the heteroatom-doped graphene or carbon-related electrode materials with high electrocatalytic activity for high-performance and low-cost energy storage and conversion devices.