Hierarchical ZnO/NiCo2O4/Nb2C: A Novel Counter Electrode for Platinum-Free Dye-Sensitized Solar Cells

Abstract The development of sustainable, cost-effective, and high-performance counter electrodes (CEs) remains a major challenge in dye-sensitized solar cell (DSSC) research. Although Pt remains the benchmark CE because of its excellent electrocatalytic activity and electrical conductivity, its scarcity and high cost motivate the development of efficient Pt-free alternatives. Herein, we report a novel Pt-free counter electrode based on a MOF-derived ZnO/NiCo2O4/Nb2C MXene composite for DSSC applications. The counter electrode materials were synthesized by a hydrothermal method and systematically characterized to evaluate their structural, morphological, and photovoltaic properties. X-ray diffraction analysis revealed characteristic peaks at 36.3°, 34.1°, and 40.3°, confirming the formation of ZnO, NiCo2O4, and Nb2C. The optimized ZnO/NiCo2O4/Nb2C MXene counter electrode achieved a power conversion efficiency (PCE) of 8.08%, comparable to that of Pt-based DSSCs under standard illumination. This enhanced performance is attributed to the synergistic effects of high catalytic activity, rapid charge transfer, and robust structural integrity in the MOF-derived ZnO/NiCo2O4/Nb2C MXene composite. Also, the addition of Nb2C MXene significantly enhanced the overall electrical conductivity and accelerated electron transfer kinetics at the electrolyte–electrode interface. These findings demonstrate that the ZnO/NiCo2O4/Nb2C MXene composite is a promising platinum-free counter electrode for advancing DSSCs toward practical commercialization and large-scale energy harvesting applications.