Dye-sensitized solar cells based on highly catalytic CNTs/Ti₃C₂T MXenes composite counter electrode

Establishing stable and efficient Pt-free counter electrodes (CEs) is an important challenge for dye-sensitized solar cells (DSSCs). Ti₃C₂T MXene, with its high catalytic activity and conductivity, has gained attention as a CE in DSSCs. The focus of this paper is on the preparation of Ti₃C₂T decorated carbon nanotubes (CNTs) composite electrode materials (CNTs/Ti₃C₂T), and testing their performance as CEs in DSSCs. Through a series of electrochemical tests, a CNTs/Ti₃C₂T CE exhibits good electrocatalytic activity toward iodine-based electrolytes with low charge transfer resistance, which is close to the performance of a Pt CE. The photoelectric conversion efficiency (PCE) of the CNTs/Ti₃C₂T (1.0 wt%) CE-based DSSCs reaches 5.83%, which is much higher than that of the CNTs CE (3.70%), and approximates that of the Pt CE (6.61%). We attribute the improved performance to the synergistic effect of the excellent conductivity and unique two-dimensional chemical structure of Ti₃C₂T MXene. Moreover, the photostability test of continuous light exposure shows that the CNTs/Ti₃C₂T-1.0 wt% (C/T-1.0 wt%) CE exhibits good stability to the electrolyte. Therefore, CNTs/Ti₃C₂T composites can be used as an efficient Pt-free CE for DSSCs in the future.