Surface active-site engineering in NiCoSe2/nitrogen-doped carbon dodecahedrons for efficient triiodide reduction in photovoltaics

Abstract

Constructing Pt-free counter electrode (CE) catalysts with considerable catalytic activity, conductivity, and electrochemical stability are greatly significant for improving the overall power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this work, we focus on the uniformly distributing Ni and Co elements into layered hydroxide polyhedrons that stemmed from ZIF-67 to transform an active-site enriched composite of NiCoSe2 encapsulated by the derived nitrogen-doped carbon dodecahedrons (NiCoSe2/NC) through the simple pyrolysis procedure. Benefitting from the evenly distributed catalytic sites, unique structure, and positively synergy, the resultant NiCoSe2/NC displays excellent catalytic activity in triiodide reduction reaction (IRR). Consequently, DSSCs fabricated with the optimized NiCoSe2/NC yielded an impressive PCE of 9.92 %, superior to that of the traditional Pt-based devices (8.17 %). The intrinsic mechanism for superior IRR performance of NiCoSe2/NC was mainly ascribed to the favorable adsorption energy (Ead) for capturing I3−, the highly reactive metal catalytic sites at the interface, the efficient electron-transfer pathway, and the enhanced bonding interaction between I 5p and 3d states of the dual metals, as revealed by DFT calculation. It is worthy expecting to provide an extensible pathway for developing a cost-effective composite with profitable structure to guide the synthesis of efficient catalysts in catalytic fields.