A Pt-free pristine monolithic carbon aerogel counter electrode for dye-sensitized solar cells: up to 20% under dim light illumination

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.

Rational Design of Carbon-Based Porous Aerogels with Nitrogen Defects and Dedicated Interfacial Structures toward Highly Efficient CO2 Greenhouse Gas Capture and Separation

CO₂ capture from flowing flue gases through adsorption technology is essential to reduce the emission of CO₂ to the atmosphere. The rational design of highly efficient carbon-based absorbents with interfacial structures containing interconnected porous structures and abundant adsorption sites might be one of the promising strategies. Here, we report the synthesis of nitrogen-doped carbon aerogels (NCAs) via prepolymerized phenol-melamine-formaldehyde organic aerogels (PMF) by controlling the addition amount of ZnCl₂ and the precursor M/P ratio. It has been revealed that NCAs with a higher specific surface area and interconnected porous structures contain a large amount of pyridinic nitrogen and pyrrolic nitrogen. These would act as the intrinsic adsorption sites for highly effective CO₂ capture and further improve the CO₂/N₂ separation efficiencies. Among the prepared samples, NCA-1-2 with a high micropore surface area and high nitrogen content exhibits a high CO₂ adsorption capacity (4.30 mmol g^-1 at 0 °C and 1 bar) and CO₂/N₂ selectivity (36.5 at 25 °C, IAST). Under typical flue gas conditions (25 °C and 1.01 bar), equilibrium gas adsorption analysis and dynamic breakthrough measurement associated with a high adsorption capacity of 2.65 mmol g^-1 at 25 °C and 1.01 bar and 0.81 mmol g^-1 at 25 °C and 0.15 bar. This rationally designed N-doped carbon aerogel with specific interfacial structures and high CO₂ adsorption capacity, high selectivity, and adsorption performance remained pretty stable after multiple uses.

Influence of Nitrogen and Sulfur Doping of Carbon Xerogels on the Performance and Stability of Counter Electrodes in Dye Sensitized Solar Cells

In this work, carbon xerogels (CXGs) doped with nitrogen or sulfur have been investigated as DSSC counter electrodes. CXGs have been prepared by a sol–gel method from resorcinol and formaldehyde and subsequent carbonization. Nitrogen doping has been carried out by introducing melamine into the synthesis process along with resorcinol and formaldehyde, while sulfur has been incorporated by direct reaction of the carbon material with elemental sulfur. The counter electrodes for DSSCs have been prepared by airbrushing on conductive glass (fluorine-doped tin oxide, FTO), and their electrochemical behavior has been evaluated, observing that the introduction of heteroatoms such as nitrogen or sulfur leads to an improvement in efficiency compared to the undoped material thanks to a decrease in charge transfer resistance.

Sheet-like porous MoO2/MoP nanoparticles as counter electrocatalysts for dye-sensitized solar cells

The interfacial MoO2/MoP with high power conversion efficiency promotes the development of a low-power environmental-friendly Pt-free counter electrode.

Recent Advances on Pt-Free Electro-Catalysts for Dye-Sensitized Solar Cells

Since Prof. Grätzel and co-workers achieved breakthrough progress on dye-sensitized solar cells (DSSCs) in 1991, DSSCs have been extensively investigated and wildly developed as a potential renewable power source in the last two decades due to their low cost, low energy-intensive processing, and high roll-to-roll compatibility. During this period, the highest efficiency recorded for DSSC under ideal solar light (AM 1.5G, 100 mW cm-2) has increased from ~7% to ~14.3%. For the practical use of solar cells, the performance of photovoltaic devices in several conditions with weak light irradiation (e.g., indoor) or various light incident angles are also an important item. Accordingly, DSSCs exhibit high competitiveness in solar cell markets because their performances are less affected by the light intensity and are less sensitive to the light incident angle. However, the most used catalyst in the counter electrode (CE) of a typical DSSC is platinum (Pt), which is an expensive noble metal and is rare on earth. To further reduce the cost of the fabrication of DSSCs on the industrial scale, it is better to develop Pt-free electro-catalysts for the CEs of DSSCs, such as transition metallic compounds, conducting polymers, carbonaceous materials, and their composites. In this article, we will provide a short review on the Pt-free electro-catalyst CEs of DSSCs with superior cell compared to Pt CEs; additionally, those selected reports were published within the past 5 years.

Aggregation-Induced Emission-Active Gels: Fabrications, Functions, and Applications

Chromophores that exhibit aggregation-induced emission (i.e., aggregation-induced emission luminogens [AIEgens]) emit intense fluorescence in their aggregated states, but show negligible emission as discrete molecular species in solution due to the changes in restriction and freedom of intramolecular motions. As solvent-swollen quasi-solids with both a compact phase and a free space, gels enable manipulation of intramolecular motions. Thus, AIE-active gels have attracted significant interest owing to their various distinctive properties and promising application potential. Herein, a comprehensive overview of AIE-active gels is provided. The fabrication strategies employed are detailed, and the applications of AIEgens are summarized. In addition, the gel functions arising from the AIE moieties are revealed, along with their structure-property relationships. Furthermore, the applications of AIE-active gels in diverse areas are illustrated. Finally, ongoing challenges and potential means to address them are discussed, along with future perspectives on AIE-active gels, with the overall aim of inspiring research on novel materials and ideas.

H2S-Sensing Studies Using Interdigitated Electrode with Spin-Coated Carbon Aerogel-Polyaniline Composites

In this paper, carbon aerogel (CA)-polyaniline (PANI) composites were prepared and first applied in the study of H₂S gas sensing. Here, 1 and 3 wt% of as-obtained CA powder were blended with PANI to produce composites, which are denoted by PANI-CA-1 and PANI-CA-3, respectively. For the H₂S gas-sensing studies, the interdigitated electrode (IDE) was spin-coated by performing PANI and PANI-CA composite dispersion. The H₂S gas-sensing properties were studied in terms of the sensor's sensitivity, selectivity and repeatability. IDE coated with PANI-CA composites, as compared with pristine PANI, achieved higher sensor sensitivity, higher selectivity and good repeatability. Moreover, composites that contain higher loading of CA (e.g., 3 wt%) perform better than composites with lower loading of CA. At 1 ppm, PANI-CA-3 displayed increased sensitivity of 452% at relative humidity of 60% with a fast average response time of 1 s compared to PANI.

Printed aerogels: chemistry, processing, and applications

As an extraordinarily lightweight and porous functional nanomaterial family, aerogels have attracted considerable interest in academia and industry in recent decades. Despite the application scopes, the modest mechanical durability of aerogels makes their processing and operation challenging, in particular, for situations demanding intricate physical structures. "Bottom-up" additive manufacturing technology has the potential to address this drawback. Indeed, since the first report of 3D printed aerogels in 2015, a new interdisciplinary research area combining aerogel and printing technology has emerged to push the boundaries of structure and performance, further broadening their application scope. This review summarizes the state-of-the-art of printed aerogels and presents a comprehensive view of their developments in the past 5 years, and highlights the key near- and mid-term challenges.

Transparent Cobalt Selenide/Graphene Counter Electrode for Efficient Dye-Sensitized Solar Cells with Co2+/3+-Based Redox Couple

In this study, we demonstrate a facile, one-pot, and low-temperature (∼85 °C) chemical bath method for the preparation of a composite of cobalt selenide/graphene (Co_0.85Se/Gr) as the electrocatalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs) with a cobalt-based electrolyte. The Co_0.85Se/Gr composite film was envisaged to have the advantages of both components, that is, the high electrochemical surface area of Co_0.85Se and the straight paths for electron transfer from Gr. The DSSCs with Co_0.85Se/Gr exhibited a power conversion efficiency (η) of 11.26%. According to the results of the rotating disk electrode, the film of Co_0.85Se/Gr showed a high electrocatalytic surface area (A_e) and an extremely large intrinsic heterogeneous rate constant (k₀). Furthermore, the composite film of Co_0.85Se/Gr exhibits a high transparency in the wavelength region of 400-800 nm (>82%), which implied that the corresponding electrode shall be a potential CE in rear-side illuminated DSSCs. The photovoltaic parameters of the DSSCs with Pt, Co_0.85Se, Gr, and Co_0.85Se/Gr were obtained for rear-side illumination and additionally for front- and rear-side illuminations (AM 1.5, 100 mW/cm²) using different electrolytes. As the cobalt-based electrolyte of [Co(bpy)₃]^2+/3+ exhibited a low light absorption and low overpotential for dye regeneration, a rear-side illuminated DSSC with a cobalt-based electrolyte showed the highest efficiency of 9.43 ± 0.02%, which is greater than that of the DSSC with an I^-/I₃^--based electrolyte (η = 7.63 ± 0.04%).

Recent progress on nanostructured carbon-based counter/back electrodes for high-performance dye-sensitized and perovskite solar cells

Dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) favor minimal environmental impact and low processing costs, factors that have prompted intensive research and development. In both cases, rare, expensive, and less stable metals (Pt and Au) are used as counter/back electrodes; this design increases the overall fabrication cost of commercial DSSC and PSC devices. Therefore, significant attempts have been made to identify possible substitutes. Carbon-based materials seem to be a favorable candidate for DSSCs and PSCs due to their excellent catalytic ability, easy scalability, low cost, and long-term stability. However, different carbon materials, including carbon black, graphene, and carbon nanotubes, among others, have distinct properties, which have a significant role in device efficiency. Herein, we summarize the recent advancement of carbon-based materials and review their synthetic approaches, structure-function relationship, surface modification, heteroatoms/metal/metal oxide incorporation, fabrication process of counter/back electrodes, and their effects on photovoltaic efficiency, based on previous studies. Finally, we highlight the advantages, disadvantages, and design criteria of carbon materials and fabrication challenges that inspire researchers to find low cost, efficient and stable counter/back electrodes for DSSCs and PSCs.

Doping AIE Photothermal Molecule into All-Fiber Aerogel with Self-Pumping Water Function for Efficiency Solar Steam Generation

Utilizing solar energy to generate clean water by interface solar steam generation is considered to be a promising strategy to address the challenge of global water shortage. However, it is challenge to design an idealized structure with all of the required characters such as high photothermal conversion efficiency, large surface to volume, and porous and continuous water pumping. Herein, we demonstrate a three-dimensional all-fiber aerogel (3D AFA) that can float on the water surface and continuously self-pump water. More notably, an aggregation-induced emission (AIE) photothermal molecule is doped into the 3D AFA, which is endowed with the superior capacity of transferring solar energy into heat. Combining these distinctive benefits, the presented 3D AFA exhibits a high evaporation rate (1.43 kg m^-2 h^-1) and solar-to-vapor conversion efficiency (86.5%) under irradiation of 1 sun, as well as a high evaporation rate (10.9 kg m^-2 d^-1) under natural sunlight. Besides, the designed 3D AFA possesses sustainable stability and a self-cleaning function to restrain salt deposition, and there is no significant change in the evaporation performance after many cycles in the case of seawater treatment. With a highly efficient evaporation rate and long-term sustainable solar steam generation, such 3D AFA can offer a new strategy for desalination.