FeS2/carbon tightly anchored on carbon cloth was developed as a counter electrode for dye-sensitized solar cells with efficiency and stability exceeding those of Pt.
It is very significant to obtain highly efficient, costeffective, and durable electrocatalysts toward triiodide reduction reaction (TRR) in hybrid photovoltaics. In this study, a nickelbased single-atom catalyst (SAC) (Ni-SAC) was prepared by the facile carbonization of NiPc@ZIF-8 and explored as a highly efficient Pt-free catalyst for TRR. During the carbonization process, the Ni species were separated by coordinate nitrogen atoms and distributed homogeneously within the porous carbon matrix, with the formation of the atomically dispersed Ni−N 4 active sites, revealed by the X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy. Compared to the reference porous nitrogen-doped carbon, Ni-SAC exhibited superior catalytic activity toward TRR. More importantly, Ni-SAC possessed better stability over the triiodide/iodide redox couple than the Pt counterpart during the stability test. The resultant solar cell presented an efficiency of 7.42%, comparable to that of the Pt-based device (7.69%). Additionally, the Kelvin probe force microscopy measurement revealed that the enhanced catalytic activity of Ni-SAC originated from the moderate energy level matching with the triiodide/iodide redox couple. The formation of Ni−N 4 active sites within the carbon matrix promoted the electron transferring at the interfaces of the catalyst/electrolyte. All results demonstrated that the SAC could be one of the Pt-free catalysts toward efficient TRR in hybrid photovoltaics.
Developing cost-effective and highly efficient photocathodes
toward
polysulfide redox reduction is highly desirable for advanced quantum
dot (QD) photovoltaics. Herein, we demonstrate nitrogen doped carbon
(N-C) shell-supported iron single atom catalysts (Fe-SACs) capable
of catalyzing polysulfide reduction in QD photovoltaics for the first
time. Specifically, Fe-SACs with FeN4 active sites feature
a power conversion efficiency of 13.7% for ZnCuInSe-QD photovoltaics
(AM1.5G, 100 mW/cm2), which is the highest value for ZnCuInSe
QD-based photovoltaics, outperforming those of Cu-SACs and N-C catalysts.
Compared with N-C, Fe-SACs exhibit suitable energy level matching
with polysulfide redox couples, revealed by the Kelvin probe force
microscope, which accelerates the charge transferring at the interfaces
of catalyst/polysulfide redox couple. Density functional theory calculations
demonstrate that the outstanding catalytic activity of Fe-SACs originates
from the preferable adsorption of S4
2– on the FeN4 active sites
and the high activation degree of the S–S bonds in S4
2– initiated
by the FeN4 active sites.
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