Nickel-iron alloy nanoparticle encapsulated in mesoporous nitrogen-doped carbon nanosphere as a counter electrode material for dye-sensitized solar cells

摘要

NiFe alloy nanoparticle encapsulated in mesoporous nitrogen-doped carbon sphere (MNCS) was synthesized by thermal pyrolysis of nickel hexacyanoferrate (NiHCF) precursor at 500 degrees C in argon atmosphere without additional metal catalyst and/or carbon source. NiHCF with three-dimensional open tunnels allowed the formation of MNCS featuring bimodal pore size distribution after pyrolysis. The tiny mesopores (< 4 nm) in carbon shell originated from the coordination complex of NiHCF, while the unique large mesopores (> 20 nm) in sphere resulted from the calcination. After partial removal of uncovered NiFe nanoparticles, the remaining NiFe nanoparticles were encapsulated in carbon shells, forming the NiFe@MNCS core-shell nanostructures. The NiFe@MNCS turned out to have superior electrocatalytic performance for I-/I-3(-) couple than the MNCS only. With protective carbon shell, the corrosion of NiFe anoparticles in I-/I-3(-) redox electrolyte could be considerably mitigated, leading to an improved longterm stability. Although the NiFe@MNCS electrode revealed slightly higher diffusion impedance, it showed a lower charge-transfer resistance than Pt. Thus, the power conversion efficiency of dyesensitized solar cell (DSSC) achieved by employing the NiFe@MNCS counter could attain 7.6%, similar to that of DSSC using Pt (7.8%). (C) 2016 Elsevier B.V. All rights reserved.