Introduction of selenium-doped CoNi2S4@MoSe2/N-MWCNTs as a high-performance counter electrode for dye-sensitized solar cells

The commercial viability of dye-sensitized solar cells (DSSCs) depends on developing cost-effective counter electrodes (CEs) with high electrocatalytic activity for the triiodide reduction reaction. Herein, a ternary hybrid electrocatalyst comprising selenium-doped cobalt nickel sulfide hollow spheres coated with molybdenum diselenide anchored on nitrogen-modified multi-walled carbon nanotubes (named as Se- CoNi 2 S 4 @MoSe 2 /N-MWCNTs) is synthesized via a two-step hydrothermal method. Its application as a CE in DSSC is studied both experimentally and theoretically. Electrochemical analysis reveals that the Se- CoNi 2 S 4 @MoSe 2 /N-MWCNTs heterostructure possesses enhanced electrocatalytic activity and reduced charge-transfer resistance at the electrolyte/electrode interface. The catalyst achieves a power conversion efficiency (PCE) of 8.62% when employed as a DSSC counter electrode, compared to 7.01% for conventional Pt. This enhanced activity is attributed to three interconnected electrochemical factors: (i) selenium doping modulating the electronic structure of the Se- CoNi 2 S 4 ; (ii) the formation of a heterojunction between Se- CoNi 2 S 4 and MoSe 2 facilitating interfacial charge transport; and (iii) the high conductivity of the N-MWCNT framework promoting rapid electron transport to catalytic sites. Moreover, computational results corroborate these findings, showing a reduced bandgap in the Se- CoNi 2 S 4 @MoSe 2 /N-MWCNTs composite, indicating that coupling Se- CoNi 2 S 4 @MoSe 2 with N-MWCNTs facilitates electron transfer.