Iron-doping and facet engineering of NiSe octahedron for synergistically enhanced triiodide reduction activity in photovoltaics

Reasonable design of cost-effective counter electrode (CE) catalysts for triiodide (I 3 − ) reduction reaction (IRR) by simultaneously combining heteroatom doping and facet engineering is highly desired in iodine-based dye-sensitized solar cells (DSSCs), but really challenging. Herein, the density function theory (DFT) calculations were first conducted to demonstrate that the Fe-doped NiSe (1   1   1) showed an appropriate adsorption energy for I 3 − , increased number of metal active sites, reinforced charge-transfer ability, and strong interaction between 3 d states of metal sites and 5 p state of I 1 atoms in I 3 − , compared to NiSe (1   1   1). Based on this finding, the well-defined Fe-NiSe octahedron with exposed (1   1   1) plane (marked as Fe-NiSe (1   1   1)) and NiSe octahedron with the same exposed plane (named as NiSe (1   1   1)) are controllably synthesized. When the as-prepared Fe-NiSe (1   1   1) and NiSe (1   1   1) worked as CE catalysts, Fe-NiSe (1   1   1) exhibits improved electrochemical performance with higher power conversion efficiency (PCE) than NiSe (1   1   1), providing new opportunity to replace precious Pt for DSSCs.