Morphology-controlled fabrication of NiCo2S4 nanostructures decorating carbon nanofibers as low-cost counter electrode for efficient dye-sensitized solar cells

Iron-doping and facet engineering of NiSe octahedron for synergistically enhanced triiodide reduction activity in photovoltaics

Reasonable design of cost-effective counter electrode (CE) catalysts for triiodide (I3-) reduction reaction (IRR) by simultaneously combining heteroatom doping and facet engineering is highly desired in iodine-based dye-sensitized solar cells (DSSCs), but really challenging. Herein, the density function theory (DFT) calculations were first conducted to demonstrate that the Fe-doped NiSe (111) showed an appropriate adsorption energy for I3-, increased number of metal active sites, reinforced charge-transfer ability, and strong interaction between 3d states of metal sites and 5p state of I1 atoms in I3-, compared to NiSe (111). Based on this finding, the well-defined Fe-NiSe octahedron with exposed (111) plane (marked as Fe-NiSe (111)) and NiSe octahedron with the same exposed plane (named as NiSe (111)) are controllably synthesized. When the as-prepared Fe-NiSe (111) and NiSe (111) worked as CE catalysts, Fe-NiSe (111) exhibits improved electrochemical performance with higher power conversion efficiency (PCE) than NiSe (111), providing new opportunity to replace precious Pt for DSSCs.

Nanograss-Assembled NiCo2S4 as an Efficient Platinum-Free Counter Electrode for Dye-Sensitized Solar Cell

Dye-sensitized solar cells (DSSCs) are often viewed as the potential future of photovoltaic systems and have garnered significant attention in solar energy research. In this groundbreaking research, we introduced a novel solvothermal method to fabricate a unique "grass-like" pattern on fluorine-doped tin oxide glass (FTO), specifically designed for use as a counter electrode in dye-sensitized solar cell (DSSC) assemblies. Through rigorous structural and morphological evaluations, we ascertained the successful deposition of nickel cobalt sulfide (NCS) on the FTO surface, exhibiting the desired grass-like morphology. Electrocatalytic performance assessment of the developed NCS-1 showed results that intriguingly rivaled those of the acclaimed platinum catalyst, especially during the conversion of I3 to I- as observed through cyclic voltammetry. Remarkably, when integrated into a solar cell assembly, both NCS-1 and NCS-2 electrodes exhibited encouraging power conversion efficiencies of 6.60% and 6.29%, respectively. These results become particularly noteworthy when compared to the 7.19% efficiency of a conventional Pt-based electrode under similar testing conditions. Central to the performance of the NCS-1 and NCS-2 electrodes is their unique thin and sharp grass-like morphology. This structure, vividly showcased through scanning electron microscopy, provides a vast surface area and an abundance of catalytic sites, pivotal for the catalytic reactions involving the electrolytes in DSSCs. In summation, given their innovative synthesis approach, affordability, and remarkable electrocatalytic attributes, the newly developed NCS counter electrodes stand out as potent contenders in future dye-sensitized solar cell applications.

Design of blueberry anthocyanin/TiO2 composite layer-based photoanode and N-doped porous blueberry-derived carbon-loaded Ni nanoparticle-based counter electrode for dye-sensitized solar cells

P25/PBP (TiO₂, anthocyanins) prepared by combining PBP (blueberry peels) with P25, and N-doped porous carbon-supported Ni nanoparticles (Ni@NPC-X) prepared using blueberry-derived carbon were used for the application as photoanode and the counter electrode, respectively, in dye-sensitized solar cells (DSSCs) to create a new perspective for blueberry-based photo-powered energy systems. PBP was introduced into the P25 photoanode and carbonized to form a C-like structure after annealing that improved its adsorption capacity for N719 dye, contributing a 17.3% higher power conversion efficiency (PCE) of P25/PBP-Pt (5.82%) than that of P25-Pt (4.96%). The structure of the porous carbon changes from a flat surface to a petal-like structure due to the N doping by melamine, and the specific surface area increases. N-doped three-dimensional porous carbon supported the loading and reduced the agglomeration of Ni nanoparticles, reducing the charge transfer resistance, and providing a fast electron transfer path. The doping of Ni and N on the porous carbon worked synergistically to enhance the electrocatalytic activity of the Ni@NPC-X electrode. The PCE of the DSSCs assembled by Ni@NPC-1.5 and P25/PBP was 4.86%. Also, the Ni@NPC-1.5 electrode exhibited 116.12 F g^-1 and a capacitance retention rate of 98.2% (10 000 cycles), further confirming good electrocatalysis and cycle stability.

Adsorption Thermodynamic and Kinetic Mechanism of Substrate-Induced Molecular Geometry Orientation

N719 dye (cis-[Ru(4-carboxy-4'-carboxylate-2,2'-bipyridine)₂(NCS)₂]) contains two carboxylic acid/carboxylate groups and two isothiocyanato (NCS) ligands and exhibit different spatial adsorption orientations during adsorption on different substrate surfaces. However, the effect of spatially adsorption orientations on the adsorption process has been rarely reported. This paper presents a detailed study of the adsorption kinetics and thermodynamics of N719 molecules based on a quartz crystal microbalance under variable temperature conditions using TiO₂ or Au substrate surfaces to induce changes in the geometrical orientation molecules. This work also reveals the adsorption properties of carboxylate groups and NCS ligands acting as anchoring groups. Research results have shown that the surface N719 molecular density of the TiO₂ substrate is higher than that of the Au substrate. Adsorption kinetics have shown that the adsorption rate of N719 molecules on the Au substrate surface with NCS ligands as anchor groups is slightly higher than that of carboxylate as the anchor groups on the TiO₂ substrate surface, and in the case of the former adsorption mode, the desorption is more pronounced. Under two different spatial orientation adsorption modes, both exhibit physical adsorption. The thermodynamics of molecular adsorption with different spatial orientations show that all adsorption processes are spontaneous and endothermic. This work is beneficial for understanding the mechanism of adsorption of dye molecules, dye molecule synthesis method, ligand selection, and improvement of device efficiency.

Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport, and mechanical flexibility. Over the past years, the integration of metal sulfides with electrospun nanomaterials has emerged as an exciting research topic owing to the synergistic effects between the two components, leading to novel and interesting properties in energy, optics and catalysis research fields for example. In this review, we focus on the recent development of the preparation of electrospun nanomaterials integrated with functional metal sulfides with distinct nanostructures. These functional materials have been prepared via two efficient strategies, namely direct electrospinning and post-synthesis modification of electrospun nanomaterials. In this review, we systematically present the chemical and physical properties of the electrospun nanomaterials integrated with metal sulfides and their application in electronic and optoelectronic devices, sensing, catalysis, energy conversion and storage, thermal shielding, adsorption and separation, and biomedical technology. Additionally, challenges and further research opportunities in the preparation and application of these novel functional materials are also discussed.