Synergistic effect of interface and defect engineering of MoC/MoO nano dot encapsulated N-doped carbon nanoflowers for highly durable dye-sensitized solar cells.

The design and fabrication of advanced counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) are limited by the scarcity of active sites and poor durability. Herein, we report the controlled preparation of a heterostructured nanoreactor CE based on defect-rich N-doped carbon nanoflowers (NCF) encapsulating MoC/MoO nano dots (NDs) in a well-defined heterophase (MoC/MoO-NCF). The MoC/MoO NDs were uniformly dispersed on the NCF, and the NCF limited the size of the MoC/MoO NDs and prevented their agglomeration, thus maximizing the electrochemically active surface area of MoC/MoO. Moreover, the synergistic effect between the MoC/MoO interface and the N-defects is conducive to the full exposure of the active sites. Furthermore, theoretical calculations revealed that the MoC/MoO heterojunction played a unique role in modulating the electronic structure and regulating the adsorption energy of tri-iodide in the iodide reduction reaction. The MoC/MoO-NCF CEs in DSSCs demonstrated a power conversion efficiency (PCE) of 9.92% and high durability, exceeding the PCE (8.36%) and durability of Pt CEs. Overall, this study offers insights into the controlled synthesis of high-performance Mo-based composite CE materials for DSSCs.