Quasi-high-entropy alloy CoNiCuMnCd/NC directly derived from ZIF-type MOFs as counter electrode catalysts for dye-sensitized solar cells

Abstract

High-entropy alloys (HEAs) as counter electrode (CE) catalysts can promote the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), due to their intrinsic characteristics of the high configurational entropy, lattice distortion, delayed diffusion and cocktail effects. Herein, five transition metal (Co, Ni, Cu, Mn and Cd) ions were combined with 2-methylimidazole to assemble ZIF-type metal-organic frameworks (MOFs) as sacrificial precursors. Then, the four transition metal alloy/N-doped carbon (NC) catalysts (CoNi/NC, CoNiCu/NC, CoNiCuMn/NC, and CoNiCuMnCd/NC) were derived respectively from precursors via pyrolysis in N 2 under high temperature. The structural characteristics of alloys were confirmed through XRD, XPS, TEM, SEM, and N 2 adsorption/desorption. Electrochemical characterization including EIS, Tafel, and CV presented that CoNiCuMnCd/NC achieved the lowest R ct (1.36 Ω cm 2 ), largest J 0 (4.87 mA cm −2 ), narrowest Δ E pp (0.204 V) and highest | I p | (2.384 mA cm −2 ) for I 3 − /I − shuttles regeneration. The J-V results show that the PCE of DSSCs assembled with CoNiCuMnCd/NC CE reaches 7.44%, which is superior to CoNi/NC (6.09%), CoNiCu/NC (6.37%), CoNiCuMn/NC (6.98%), and even Pt (6.95%). The CoNiCuMnCd/NC based on entropy-driven design can be classified as quasi-HEA, which optimize electron transfer, adsorption energy, and interface energy alignment, thereby providing a high-performance and cost-effective way to select catalysts for photovoltaic application in DSSCs.