Metal-organic framework-derived Ni-Co alloy@carbon microspheres as high-performance counter electrode catalysts for dye-sensitized solar cells

Spherical-structured nano-/micromaterials with tunable shell architectures and compositions are becoming increasingly important and attractive for electrochemical energy conversion and storage. Herein, we report the synthesis of novel Ni-Co alloy@carbon microspheres by calcining Co/Ni bimetallic metal-organic frameworks (MOFs) prepared by a facile solvothermal reaction. Their structures, dimensions and electrochemical performance can be optimized by simply tuning the Co/Ni molar ratio. Benefiting from the advantageous structural and compositional features, the obtained Ni-Co alloy@carbon microspheres display exceptional electrochemical performance when used as counter electrode (CE) catalysts for dye-sensitized solar cells (DSSCs). In particular, the optimized NiCo0.2@C CE delivers an impressive power conversion efficiency (PCE) of 9.30%, showing a similar to 15.7% enhancement compared to that of Pt CE (8.04%). Additionally, the NiCo0.2@C CE also demonstrates a good long-term electrochemical stability for the I-3 (-)/I- electrolyte. This work may provide new options for the design and preparation of efficient electrocatalysts with novel morphologies and desirable compositions.