Nickel-Based Single-Atom Catalyst toward Triiodide Reduction Reaction in Hybrid Photovoltaics

Abstract

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.

Molybdenum-Single Atom Catalyst for High-Efficiency Cobalt(III)/(II)-Mediated Hybrid Photovoltaics

“…X-ray diffraction (XRD) patterns of the Mo–N–C sample only presented a broad diffraction peak at 43.2°, extremely similar to that of the reference N–C sample (Figure S2). No other peaks from oxides and metal were detected, indicating no formation of other Mo-related NPs.…”

“…High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) images revealed that the as-obtained Mo−N−C sample presented rhombic dodecahedral morphologies (Figure 1b,c), which are similar to those observed from the reference N−C sample S2). 34 No other peaks from oxides and metal were detected, indicating no formation of other Mo-related NPs. Furthermore, Raman spectra revealed that the N-doped carbon support has abundant defects in the Mo−N−C and N− C catalysts (Figure S3).…”

“…To clarify the improvement in PCE, surface potentials of the Mo−N−C and the reference N−C were measured using a Kelvin probe force microscope (KPFM). 34,41,42 KPFM is a powerful tool, which has been widely utilized to obtain the information about the local structure, composition, and electronic state of catalysts. 41 More importantly, the imaging of surface potential can be enabled by KPFM for a broad range of nanomaterials.…”

“…Previous studies have demonstrated that surface potential is very sensitive to the surface modifications. 34,41,42 The three-dimensional illustration of the relative surface potential of the N−C and Mo−N−C samples is…”

Efficient NiO Impregnated Walnut Shell-Derived Carbon for Dye-Sensitized Solar Cells

“…However, due to the poor electrical and ionic conductivity, the overall performance is rather low. To alleviate this problem, NiO nanoparticles have been combined with several conductive materials. − Carbon materials demonstrated a potential ability to enhance the conductivity of NiO and hence the overall performance of DSSC via the synergistic effect . Recently, a NiO-multiwalled carbon nanotubes (MWCNTs) composite was prepared and utilized as CE for DSSCs, the assembled device exhibited a PCE of 3.80% .…”