Carbon paper supported cactus-like Mn-Co-Ni oxide composites as a high-performance counter electrode for dye-sensitized solar cells

n dye-sensitized solar cells (DSSCs), the counter electrodes (CEs) functions both as an electron collector from the peripheral circuitry and as a catalytic platform for regenerating the redox couple (I − /I 3 − ) in the electrolyte. Although Pt offers excellent catalytic activity, its high cost and instability limit practical use. Transition metal oxides are promising Pt alternatives but have low conductivity and inadequate catalytic performance. Here, we synthesized a cactus-like Mn-Co-Ni oxide composite on carbon paper (MnCoNiO/CP) via a two-stage process combining hydrothermal treatment with subsequent annealing. The hierarchical structure provided a high specific surface area (67.753 m 2 ·g −1 ), abundant active sites, and enhanced conductivity. The MnCoNiO/CP-based DSSCs exhibited a photovoltaic performance characterized by an open-circuit voltage (V oc ) of 0.807 V, short-circuit current density (J sc ) reaching 17.86 mA·cm −2 , and fill factor (FF) attaining 0.7, culminating in an overall power conversion efficiency (PCE) of 10.04 %. This corresponds to a 34.8 % enhancement in PCE compared to the Pt electrode (7.45 %) under identical conditions. The performance improvement directly correlates with the unique cactus-like morphology and the synergistic effects of the multi-component oxides. This work introduces a cost-effective strategy for developing enhanced-functionality CEs in DSSCs and other applications.