MXene/NiCo2S4 2D/3D Heterostructure as a High-Performance Pt-Free Counter Electrode for DSSCs

This study represents a novel 2D/3D heterostructure of MXene/NiCo 2 S 4 composites, which were used for the first time as a high-performance counter-electrode material for Pt-free dye-sensitized solar cells (DSSCs). The unique morphology of 2D-MXene/3D-NiCo 2 S 4 proved advantageous in producing good electrode/electrolyte interfacial contact, enhancing the electrocatalytic activity via vigorous electron transfer and ion diffusion. Cyclic voltammetry, Tafel polarization, and electrochemical impedance spectroscopy measurements confirmed that hierarchical interconnection and aggregation of 2D-MXene sheets/3D-NiCo 2 S 4 nanoparticles lead to both fast charge transport and rapid redox reaction kinetics. Consequently, the DSSC device assembled with the 2D-MXene/3D-NiCo 2 S 4 counter electrode exhibited a higher photovoltaic conversion efficiency of up to 8.76 % compared to that of the standard Pt counter electrode-assembled device (8.46 %). These findings offer a perspective design concept for materializing the Pt-free, high-performance 2D/3D hierarchical heterostructure as a superb counter electrode of next-generation photovoltaic devices. • A novel 2D/3D heterostructure of MXene/NiCo 2 S 4 was prepared by probe sonication. • MXene-NiCo 2 S 4 hybridization improved charge transport and redox reaction kinetics. • MXene/NiCo 2 S 4 exhibited excellent performance as a counter electrode of DSSC. • MXene/NiCo 2 S 4 -based DSSC demonstrated an improved efficiency of 8.76 %. • These findings offer a perspective design concept for realizing the Pt-free DSSC.