Spherical Fe7S8@rGO nanoflowers as electrodes with high electrocatalytic performance in dye-sensitized solar cells.

Dye-sensitized solar cells (DSSCs) can directly convert solar energy into electricity, and have aroused great research interest from researchers. Here, the spherical Fe7S8@rGO nanocomposites were expediently fabricated by facile methods, and applied in DSSCs as counter electrodes (CEs). The morphological features show the porous structure of Fe7S8@rGO, and it is beneficial to enhance the permeability of ions. Reduced graphene oxide (rGO) has a large specific surface area and good electrical conductivity, shortening the electron transfer path. The presence of rGO promotes the catalytic reduction of I3- ions to I- ions and reduces the charge transfer resistance (Rct). The experimental findings show that the power conversion efficiency (PCE) of Fe7S8@rGO as CEs for DSSCs can reach 8.40% (20 wt% for rGO), significantly higher than Fe7S8 (7.60%) and Pt (7.69%). Therefore, Fe7S8@rGO nanocomposite is expected to be an efficient and cost-effective CE material for DSSCs.

MoS2 Nanosheets Decorated with Fe3O4 Nanoparticles for Highly Efficient Solar Steam Generation and Water Treatment.

The shortage of water resources has always been one of the most difficult problems that perplexes humanity. Solar steam generation (SSG) has been a new non-polluting and low-cost water purification method in recent years. However, the high cost of traditional photothermal conversion materials and the low efficiency of photothermal conversion has restricted the large-scale application of SSG technology. In this work, composite materials with Fe3O4 nanospheres attached to MoS2 nanosheets were synthesized, which increased the absorbance and specific surface area of the composite materials, reduced the sunlight reflection, and increased the photothermal conversion efficiency. During the experiment, the composite material was evenly coated on cotton. The strong water absorption of cotton ensured that the water could be transported sufficiently to the surface for evaporation. Under one sun irradiation intensity, the evaporation rate of the sample synthesized in this work reached 1.42 kg m-2 h-1; the evaporation efficiency is 89.18%. In addition, the surface temperature of the sample can reach 41.6 °C, which has far exceeded most photothermal conversion materials. Furthermore, the use of this composite material as an SSG device for seawater desalination and sewage purification can remove more than 98% of salt ions in seawater, and the removal rate of heavy metal ions in sewage is close to 100%, with a good seawater desalination capacity and sewage purification capacity. This work provides a new idea for the application of composite materials in the field of seawater desalination and sewage purification.

Flower-Shaped Carbon Nanomaterials for Highly Efficient Solar-Driven Water Evaporation.

Solar-driven interface water evaporation is an energy-saving, environmentally friendly, and efficient seawater desalination and wastewater treatment technology. However, some challenges still restrict its further industrial development, such as its complex preparation, heavy metal pollution, and insufficient energy utilization. In this study, a photothermal layer based on flower-shaped carbon nanoparticles is presented for highly efficient solar-driven interface evaporation for water treatment applications. The results show that the surface of the prepared carbon nanomaterials presents a flower-shaped structure with an excellent light absorption capacity and a large specific surface area. Moreover, the C-5.4 (Carbon-5.4) sample has an evaporation rate of 1.87 kg/m2/h and an evaporation efficiency of 87%-far higher than most photothermal materials. In addition, carbon nanomaterials have an excellent ion scavenging capacity, dye purification capacity, and outdoor practical performance. This study provides a new solution for the application of carbon nanomaterials in the field of water purification.

Fe3O4/Diatomite-Decorated Cotton Evaporator for Continuous Solar Steam Generation and Water Treatment.

Improving the evaporation rate of solar steam generation (SSG) has always been a research hotspot to solve the shortage of water resources. Using cotton, Fe3O4, polyvinyl alcohol (PVA) and diatomite (DM) as raw materials, DM/PVA/Fe3O4@cotton composites with both firmness and hydrophilicity were prepared. Fe3O4 has a wide range of light absorption characteristics and good photothermal conversion performance, and is an ideal photothermal conversion material. PVA enhances the adhesion between Fe3O4, cotton and DM and enhances the hardness of the sample and the internal porous structure. The existence of DM greatly improves the hydrophilicity of the sample, ensuring that the water in the lower layer can be continuously transported to the surface of the sample, and DM makes the surface of the sample rough, which reduces the reflection of sunlight and improves the efficiency of light heat conversion. Under one-sun irradiation, the temperature of the sample surface increases by 52.6 °C, the evaporation rate can reach 1.32 kg m-2 h-1 and the evaporation efficiency is 82.9%. Using this sample as the photothermal conversion layer of the SSG device, the removal rate of salt ions in seawater is more than 98% and the removal rate of heavy metal ions in sewage is close to 100%. This work provides a new idea and design method for SSG in the field of seawater desalination and sewage treatment.

Remarkable Enhancement in the Photoelectric Performance of Uniform Flower-like Mesoporous Fe3O4 Wrapped in Nitrogen-Doped Graphene Networks.

The porous structure and excellent specific surface area are superior for use as a counter electrode (CE) material. In addition, N-doped graphene possesses a remarkable electron-transfer pathway and many active sites. Therefore, a novel idea is to wrap uniform flower-like mesoporous Fe3O4 (Fe3O4UFM) in an N-doped graphene (N-RGO) network structure to enhance the power conversion efficiency (PCE). The hybrid materials of Fe3O4UFM@N-RGO are first used as a CE in dye-sensitized solar cells (DSSCs), showing a preeminent conductive interconnected 3D porous structure with more catalytic activity sites and a better ability for and a faster reaction rate of charge transfer, resulting in quicker reduction of I3- than Pt. A 9.26% photoelectric conversion efficiency has been achieved for the DSSCs with Fe3O4UFM@N-RGO as the CE, which is beyond the value of Pt (7.72%). The positive synergetic effect between Fe3O4 and N-RGO is mainly responsible for the remarkable photoelectric property enhancement of this uniform flower-like mesoporous Fe3O4 wrapped in N-doped graphene networks, as demonstrated by the Tafel polarization, electrochemical impedance spectra, and CV curves. These methods will provide a simple way to effectively reproduce CE materials.

Functional integration and self-template synthesis of hollow core-shell carbon mesoporous spheres/Fe3O4/nitrogen-doped graphene to enhance catalytic activity in DSSCs.

Excellent corrosion resistance is crucial for photovoltaic devices to acquire high and stable performance under high corrosive complicated environments. Creative inspiration comes from sandwich construction, whereby Fe3O4 nanoparticles were anchored onto hollow core-shell carbon mesoporous microspheres and wrapped by N-graphene nanosheets (HCCMS/Fe3O4@N-RGO) to obtain integrated high corrosive resistance and stability. The as-prepared multiple composite material possesses outstanding performance as a result of structure optimization, performance improvement, and interface synergy. Therefore, it can effectively suppress corrosion from the electrolyte in recycled tests many times, indicating the ultrahigh corrosion resistance life of this double carbon-based nanocomposite. Furthermore, the electrical conductivity and conversion efficiency of the composite are well maintained due to the triple synergistic interactions, which could serve as a guideline in establishing high-performance multifunctional HCCMS/Fe3O4@N-RGO with great prospects in energy devices, such as lithium batteries, supercapacitors and electrode materials, etc.