Design and construction of MoS2/Ni3S2 nanosheets decorated on multi-walled carbon nanotubes as a sustainable counter electrode for dye-sensitized solar cells: An experimental and computational investigation

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To achieve a satisfactory photovoltaic performance in dye-sensitized solar cells (DSSCs), counter electrode (CE) catalysts with low cost, superior catalytic activity and excellent conductivity should be developed. Herein, we successfully prepared the MoS2/Ni3S2 heterostructures via the hydrothermal method and decorated on multi-walled carbon nanotubes (MWCNTs) by sonication method. The performance of the prepared CEs was investigated by various electrochemical techniques. Based on the electrochemical tests, the MoS2/Ni3S2/MWCNTs ternary nanocomposite displayed high electron transfer ability, remarkable catalytic activities, and good stability in the I3−/I− electrolyte. The power conversion efficiency (PCE) of DSSCs based on MoS2/Ni3S2/MWCNTs CE reached 8.27 %, which was even higher than that of the DSSC with Pt CE (7.23 %). The excellent performance of the catalyst is related to the structural properties, synergistic effect of MoS2/Ni3S2 and MWCNTs, and high porosity of MoS2/Ni3S2/MWCNTs composite. The results of calculations indicated that by decorating the MoS2/Ni3S2 on carbon nanotubes (CNTs), the bandgap decreased to 2.79 eV, which was smaller than the individual CNTs (6.27 eV). This finding depicted that synergistic effect between MoS2/Ni3S2 and MWCNTs can reduce the bandgap of MoS2/Ni3S2/MWCNTs composite. The lower bandgap mostly results in higher electrical conductivity and lower charge-transfer resistance, which plays an important role in improving the efficiency of DSSCs.