Fabrication of Mesoporous CoS₂ Nanotube Arrays as the Counter Electrodes of Dye‐Sensitized Solar Cells

Abstract

Mesoporous cobalt sulfide nanotube arrays on FTO-coated glass were synthesized by combining three simple technologies: the selective etching of ZnO sacrificial templates, mesoporous Co3 O4 formation from cobalt-chelated chitosan, and ion-exchange reaction (IER). The mesoporous Co3 O4 nanotubes composed of the Co3 O4 nanoparticles possess a high surface area and are taken advantage for further removal of templates and IER. The morphologies and crystal structures of the CoS2 nanotube arrays were characterized by SEM, TEM, and XRD analyses. Their electrocatalytic properties were determined by electrochemical analyses including cyclic voltammetry measurements and Tafel polarization. The DSSCs assembled with a CoS2 counter electrode achieved a power conversion efficiency of 6.13 %, which was comparable to that of the DSSC with the Pt counter electrode (6.04 %). This indicates that the mesoporous CoS2 nanotube array can be a low-cost and efficient alternative for the reduction of electrolytes in DSSCs.

Effect of Co Doping on Electrocatalytic Performance of Co-NiS2/CoS2 Heterostructures

“…When the proportion of Co doping reaches 27%, the regular crystal basically disappears, and only irregular coral flowerlike structure can be seen on the carbon fiber. S2a and S3a, in order to analyze the activity difference between Co-NiS 2 /CoS 2 heterostructures and undoped NiS 2 , we measured different scanning rates (5,10,20,30,40,50,60,70,80, 90 and 100) by cyclic voltammetry (CV). As shown in Figures S2b and S3b, the electrochemical surface area (ECSA) of undoped and 27% doped Faraday double-layer capacitor (Cdl) is obtained.…”

“…As shown in Figure 2 a and Supplementary Figure S4 , undoped pure NiS 2 nanomaterial shows regular crystal structure and smooth surface. With the increase in Co doping concentration, the regular crystal structure changes to a coral flower shape, and the wheat spike structure can be observed in the further enlarged image, which is conducive to the exposure of the catalytic active centers, thereby improving the catalytic efficiency [ 30 , 31 ]. When the Co content reaches up to 27%, the Co-NiS 2 /CoS 2 heterostructures has the largest catalytic active region and the best electrocatalytic performance.…”

Two-dimensional transition metal dichalcogenide-based counter electrodes for dye-sensitized solar cells

“…[226][227][228][229][230][231] The properties of CoS 2 nanocrystalline thin films prepared by a hydrothermal method were reported by Jin et al 232 Another study used mesoporous CoS 2 nanotube arrays deposited on an FTO glass substrate and used as a CE for a DSSC. 233 In another study, CoS 2 /graphene composites were prepared via a hydrothermal method using Co ions with thiourea in the presence of graphene oxide (GO). 239 The distribution and size of the CoS 2 nanoparticles deposited onto a flexible graphene sheet was controlled in order to optimize the electrocatalytic activity for I 3 − reduction.…”

“…[226][227][228][229][230][231] The properties of CoS 2 nanocrystalline thin films prepared by a hydrothermal method were reported by Jin et al 232 Another study used mesoporous CoS 2 nanotube arrays deposited on an FTO glass substrate and used as a CE for a DSSC. 233 The CoS 2 nanotube arrays were characterized by SEM, TEM, and XRD techniques for their morphology and crystal structures. The electrocatalytic properties of the CoS 2 nanotube arrays were measured using CV and Tafel polarization curve measurements.…”

“…This indicates better electrochemical stability of the TiS 2 -graphene hybrid CE than the Pt CE. The stability of photovoltaic parameters of DSSCs having mesoporous CoS 2 nanotube arrays as CEs was recorded for 10 days by Tsai et al233 A slight drop in the V OC and FF values were observed, which resulted in a 2.2% decrease in the PCE of the CoS 2 nanotube array CEs. The photovoltaic parameters of the DSSC were quite stable up to 10 days, indicating good stability of DSSCs with mesoporous CoS 2 nanotube array CEs…”