Transition-metal-based Catalysts for Electrochemical Synthesis of Ammonia by Nitrogen Reduction Reaction: Advancing the Green Ammonia Economy.

Ammonia (NH3 ), a cornerstone in the chemical industry, has historically been pivotal for producing various valuable products, notably fertilizers. Its significance is further underscored in the modern energy landscape, where NH3 is seen as a promising medium for hydrogen storage and transportation. However, the conventional Haber-Bosch process, which accounts for approximately 170 million ton of NH3 produced globally each year, is energy-intensive and environmentally damaging. The electrochemical nitrogen reduction reaction (NRR) emerges as a sustainable alternative that operates in ambient conditions and uses renewable energy sources. Despite its potential, the NRR faces challenges, including the inherent stability of nitrogen and its competition with the hydrogen evolution reaction. Transition metals, especially ruthenium (Ru) and molybdenum (Mo), have demonstrated promise as catalysts, enhancing the efficiency of the NRR. Ru excels in catalytic activity, while Mo offers robustness. Strategies like heteroatom doping are being pursued to mitigate NRR challenges, especially the competing hydrogen evolution reaction. This review delves into the advancements of Ru and Mo-based catalysts for electrochemical ammonia synthesis, elucidating the NRR mechanisms, and championing the transition towards a greener ammonia economy. It also seeks to elucidate the core principles underpinning the NRR mechanism. This shift aims not only to address challenges inherent to traditional production methods but also to align with the overarching goals of global sustainability.

Reticular Chemistry for Optical Sensing of Anions.

In the last few decades, reticular chemistry has grown significantly as a field of porous crystalline molecular materials. Scientists have attempted to create the ideal platform for analyzing distinct anions based on optical sensing techniques (chromogenic and fluorogenic) by assembling different metal-containing units with suitable organic linking molecules and different organic molecules to produce crystalline porous materials. This study presents novel platforms for anion recognition based on reticular chemistry with high selectivity, sensitivity, electronic tunability, structural recognition, strong emission, and thermal and chemical stability. The key materials for reticular chemistry, Metal-Organic Frameworks (MOFs), Zeolitic Imidazolate Frameworks (ZIFs), and Covalent-Organic Frameworks (COFs), and the pre- and post-synthetic modification of the linkers and the metal oxide clusters for the selective detection of the anions, have been discussed. The mechanisms involved in sensing are also discussed.

Policies and regulations for solar photovoltaic end-of-life waste management: Insights from China and the USA.

The solar photovoltaic (PV) industry has experienced rapid growth in recent years, resulting in a substantial increase in the amount of end-of-life (EOL) waste generated by these panels. Proper waste management is crucial to minimize environmental and health risks. The purpose of this study is to examine the EOL solar PV waste management policies and regulations in China and the United States, identifying challenges and recommending policy implications for enhancing sustainable waste management practices. China has promulgated policies and regulations for managing PV EOL waste, including the National Solid Waste Law and GB or GB/T standards. In the US, federal regulations and guidelines such as the Resource Conservation and Recovery Act (RCRA) and state-specific hazardous waste programs, universal waste rules, and waste recycling programs are enacted. The findings of this study indicate that China and the US face distinct challenges in solar PV end-of-life waste management. China lacks comprehensive local government-level regulations, while the USA exhibits variations in coverage and specific management requirements across states. In light of these observations, as policy implications, it is recommended. Firstly, there is a need for greater harmonization between federal and local/state-level policies and regulations. Secondly, continued research and development efforts are crucial to explore cost-effective and environmentally responsible recycling and disposal options for PV panels. Furthermore, promoting collaboration among policymakers, industry stakeholders, and researchers can facilitate knowledge sharing and the exchange of best practices. Such measures will contribute to the effective and sustainable management of solar PV EOL waste in China and the USA.

The Synergy of Lead Chalcogenide Nanocrystals in Polymeric Bulk Heterojunction Solar Cells.

Photoactive polymer and quantum dots (QDs)/nanocrystals (NCs)-based bulk heterojunction (BHJ) solar cells have the combined positivity of organic semiconductors and inorganic components, which can enable a high carrier mobility and absorption coefficient. Additionally, the NCs also provide the opportunity to tune the band gap to obtain enhanced absorption in a broad solar spectrum. Among the semiconductors, lead chalcogenide NCs are of particular interest due to their good photosensitivity in the near-infrared (NIR) region of the solar spectrum. These NCs have large exciton Bohr radii (18, 46, and 150 nm for PbS, PbSe, and PbTe, respectively) and tunable sizes depending on the optical bandgaps between 0.3 and 1.5 eV. Independently, lead chalcogenide NCs have been studied extensively for different applications; however, uses in polymer-NC-based bulk heterojunction solar cells are limited. This Review has been structured on the lead chalcogenide NCs incorporated in polymer composite-based bulk heterojunction solar cells covering the material, properties, and solar cell performance to find the issues and explore future opportunities.

Clarification of the Supercooling and Heat Storage Efficiency Calculation Formula for Shape-Stabilized Phase Change Materials.

It is essential to determine the heat storage efficiency of shape-stabilized phase change materials (ss-PCMs). In two published articles, the formula for heat storage efficiency is presented using two distinct equations. Using the two equations, the calculated values for heat storage efficiency revealed significant discrepancies. The outcomes cannot be compared. The evaluation of heat storage efficiency has a substantial impact on the practical application of PCMs and serves as a performance benchmark for the PCM samples that have been tested. In this paper, the correct equations for calculating the efficiency of heat storage are presented. Furthermore, it is essential to note that the methods used to calculate the supercooling value are not straightforward. Consequently, this paper clarified the correct formula and/or method for determining the supercooling value and heat storage efficiency of ss-PCMs.

Energy Conversion Efficiency Enhancement of Polyethylene Glycol and a SiO2 Composite Doped with Ni, Co, Zn, and Sc Oxides.

Doping the SiO2 support with Co, Ni, Zn, and Sc improves the thermal conductivity of a hybrid PEG/SiO2 form-stable phase change material (PCM). Doping also improves the energy utilization efficiency and speeds up the charging and discharging rates. The thermal, chemical, and hydrothermal stability of the PEG/Zn-SiO2 and PEG/Sc-SiO2 hybrid materials is better than that of the other doped materials. The phase change enthalpy of PEG/Zn-SiO2 is 147.6 J/g lower than that of PEG/Sc-SiO2, while the thermal conductivity is 40% higher. The phase change enthalpy of 155.8 J/g of PEG/Sc-SiO2 PCM is very close to that of the parent PEG. PEG/Sc-SiO2 also demonstrates excellent thermal stability when subjected to 200 consecutive heating-cooling cycles and outstanding hydrothermal stability when examined under a stream at 120 °C for 2 h. The supercooling of the PEG/Sc-SiO2 system is the lowest among the tested materials. In addition, the developed PCM composite has a high energy storage capacity and high thermal energy storage/release rates.

Palladium Nanoparticles Supported on Cellulosic Paper as Multifunctional Catalyst for Coupling and Hydrogenation Reactions.

Hallmark of a successful catalyst is its high efficiency, economic aspects, operational simplicity, extensive reusability, higher environment friendliness, and potential use in multiple industrial applications. Herein, a facile protocol involving a catalyst with Pd nanoparticles supported on cellulose paper (also known as a "dip-catalyst") for the hydrogenation of a series of quinolines, nitroarene, and C-C bond formation reactions in most benign solvents such as water is described. The mere insertion/removal of the "dip-catalyst" strip enables instantaneous start/stop of the reaction, which enhances its reusability and ease of separation of products. Cellulose paper (CP) strips decorated with Pd nanoparticles (Pd/CP) are prepared by the reduction of K2 PdCl4 soaked strips using formic acid as reductant. The resulting spherical shaped Pd particles, confirmed by scanning electron microscopy, form stable catalysis centers on the support. XRD signature confirms the crystallinity of the Pd nanoparticles and the TEM images display 15-20 nm size particles uniformly decorating CP. X-ray photoelectron spectroscopy indicates the formation of metallic Pd. The catalyst is tested for the C-C bond formation reactions. Pd/CP catalyzed Suzuki-Miyaura coupling reaction demonstrate >99% conversion with optimum selectivity. On the other hand, Mizoroki-Heck reaction produced 87% conversion with the reaction of 4-methoxycarbonyl phenylboronic acid and iodobenzene in ethanol:water (1 : 1 v/v) using KOH as base. The developed Pd/CP construct produces >99% of the pyridine-ring hydrogenated product on quinoline hydrogenation using tetrahydroxydiboron (THDB) as the hydrogen source. Diverse and highly reducible functional groups were also evaluated for transfer hydrogenation, which demonstrates a high efficiency in terms of both reactivity and selectivity. The used catalysts are recyclable for the multiple cycles.

UV-Protected Polyurethane/f-Oil Fly Ash-CeO2 Coating: Effect of Pre-Mixing f-Oil Fly Ash-CeO2 with Monomers.

A series of UV-protected coatings were prepared using cerium-oxide-functionalized oil fly ash (f-OFA-CeO2) in waterborne polyurethane (WBPU) dispersions. Three monomers, namely, poly(tetramethyleneoxide glycol) (PTMG), polydimethylsiloxane-hydroxy terminated (PDMS) and 4,4-dicyclohexylmethane diisocyanate (H12MDI), were used to pre-mix with f-OFA-CeO2 separately, followed by the synthesis of WBPU/f-OFA-CeO2 dispersions. The f-OFA-CeO2 distribution and enrichment into any part (top/bottom/bulk) of the coating was strongly affected by the pre-mixing of f-OFA-CeO2. The f-OFA-CeO2 was densely distributed in the top, bottom and bulk when the f-OFA-CeO2 was pre-mixed with PDMS, H12MDI and PTMG, respectively. Only an f-OFA-CeO2-enriched top surface showed excellent UV protection. The lowest UV-degraded exposed coating was found when the top surface of the coating was f-OFA-CeO2-enriched.

Fluorescein Hydrazide-Appended Metal-Organic Framework as a Chromogenic and Fluorogenic Chemosensor for Mercury Ions.

In this work, we prepared a fluorescein hydrazide-appended Ni(MOF) (Metal-Organic Framework) [Ni3(BTC)2(H2O)3]·(DMF)3(H2O)3 composite, FH@Ni(MOF). This composite was well-characterized by PXRD (powder X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), N2 adsorption isotherm, TGA (thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy), and FESEM (field emission scanning electron microscopy). This composite was then tested with different heavy metals and was found to act as a highly selective and sensitive optical sensor for the Hg2+ ion. It was found that the aqueous emulsion of this composite produces a new peak in absorption at 583 nm, with a chromogenic change to a pink color visible to the naked eye upon binding with Hg2+ ions. In emission, it enhances fluorescence with a fluorogenic change to green fluorescence upon complexation with the Hg2+ ion. The binding constant was found to be 9.4 × 105 M-1, with a detection limit of 0.02 µM or 5 ppb. This sensor was also found to be reversible and could be used for seven consecutive cycles. It was also tested for Hg2+ ion detection in practical water samples from ground water, tap water, and drinking water.

Efficient Capture of Heavy Metal Ions and Arsenic with a CaY-Carbonate Layered Double-Hydroxide Nanosheet.

Nanosheets consisting of two-dimensional (2-D) nanomaterials made up of Ca2+ (Ca), and Y3+ (Y) cations and carbonate [CO3 2-] anions in the interlayer with a uniform thickness and lengths of around 10 µm have been successfully synthesized in a hydrotalcite layer structure, otherwise known as a layered double hydroxide, using a facile hydrothermal method. The resulting CaY-CO3 2- layered double-hydroxide (LDH) materials demonstrate outstanding affinity and selectivity for toxic transition metal ions such as Cr3+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, and Hg2+ as well as metalloid As3+. The adsorption of all of the highly toxic metal ions from the aqueous solution was found to be exceptionally rapid and highly selective, with more than 95% removal achieved within 30 min. For AsO3, a strong adsorption potential of 452 mg/g was observed at pH 7.0, which is better than most values previously reported. The distribution coefficient K d values can exceed ∼106 mL/g for Cr3+, Pb2+, and As3+, which are highly toxic. The fabricated materials have excellent chemical stability: they retain their well-defined lamellar shapes even under mildly acidic conditions.

Preparation of a Sustainable Shape-Stabilized Phase Change Material for Thermal Energy Storage Based on Mg2+-Doped CaCO3/PEG Composites.

The properties of polyethylene glycol-6000 (PEG)/MgCaCO3, a low-cost shape-selective phase change material (ss-PCM), make it highly suitable for solar thermal applications. Nanosized porous MgO-doped CaCO3 with Mg molar concentrations of 5%, 10%, and 15% were synthesized using a hydrothermal technique. The prepared MgO-CaCO3 matrices were then impregnated with PEG to obtain PEG/MgCaCO3 as an ss-PCM. Samples identified as PEG-5MgCaCO3 (P-5-MCC), PEG-10MgCaCO3 (P-10-MCC), and PEG-15MgCaCO3 (P-15-MCC) were prepared and studied. Interestingly, P-10-MCC has the smallest particle size together with a good porous structure compared to the other two materials. The results of thermogravimetric analyses and differential scanning calorimetry indicate that the small particle size and porous structure facilitate the impregnation of approximately 69% of the PEG into the 10-MCC matrix. The latent heat and energy storage efficiency of PEG in the P-10-MCC sample are 152.5 J/g and 96.48%, respectively, which are significantly higher than those of comparable materials. Furthermore, in addition to the improvement of the thermal conductivity of the P-10-MCC, its supercooling is also reduced to some extent. The combined mesoporous and macro-porous structure of P-10-MCC is critical to retaining a large amount of PEG within the matrix, resulting in a high latent heat in the operating temperature range of 35-57 °C. The P-10MCC sample also demonstrates a high energy storage capacity (98.59%), high thermal energy storage/release rates, and exceptional shape-stabilized PCM properties.

Preparation of Hierarchical Porous Activated Carbon from Banana Leaves for High-performance Supercapacitor: Effect of Type of Electrolytes on Performance.

We demonstrate a facile efficient way to fabricate activated carbon nanosheets (ACNSs) consisting of hierarchical porous carbon materials. Simply heating banana leaves with K2 CO3 produce ACNSs having a unique combination of macro-, meso- and micropores with a high specific surface area of ∼1459 m2 g-1 . The effects of different electrolytes on the electrochemical supercapacitor performance and stability of the ACNSs are tested using a two-electrode system. The specific capacitance (Csp ) values are 55, 114, and 190 F g-1 in aqueous 0.5 M sodium sulfate, organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile, and pure ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6 ]) electrolytes, respectively. The ACNSs also shows the largest potential window of 3.0 V, the highest specific energy (59 Wh kg-1 ) and specific power (750 W kg-1 ) in [BMIM][PF6 ]. A mini-prototype device is prepared to demonstrate the practicality of the ACNSs.

Multi Self-Healable UV Shielding Polyurethane/CeO2 Protective Coating: The Effect of Low-Molecular-Weight Polyols.

We prepared a series of polyurethane (PU) coatings with defined contents using poly(tetramethylene oxide)glycol (PTMG) with two different molecular weights (i.e., Mn = 2000 and 650), as well as polydimethyl siloxane (PDMS) with a molecular weight of Mn 550. For every coating, maximum adhesive strength and excellent self-healing character (three times) were found using 6.775 mol% mixed with low-molecular-weight-based polyols (PU-11-3-3). Defined 1.0 wt% CeO2 was also used for the PU-11-3-3 coating (i.e., PU-11-3-3-CeO2) to obtain UV shielding properties. Both the in situ polymerization and blending processes were separately applied during the preparation of the PU-11-3-3-CeO2 coating dispersion. The in situ polymerization-based coating (i.e., PU-11-3-3-CeO2-P) showed similar self-healing properties. The PU-11-3-3-CeO2-P coating also showed excellent UV shielding in real outdoor exposure conditions.

Shape-Stabilized Phase Change Materials for Solar Energy Storage: MgO and Mg(OH)2 Mixed with Polyethylene Glycol.

Heat energy storage systems were fabricated with the impregnation method using MgO and Mg(OH)2 as supporting materials and polyethylene glycol (PEG-6000) as the functional phase. MgO and Mg(OH)2 were synthesized from the salt Mg(NO3)·6H2O by performing hydrothermal reactions with various precipitating agents. The precipitating agents were NaOH, KOH, NH3, NH3 with pamoic acid (PA), or (NH4)2CO3. The result shows that the selection of the precipitating agent has a significant impact on the crystallite structure, size, and shape of the final products. Of the precipitating agents tested, only NaOH and NH3 with PA produce single-phase Mg(OH)2 as the as-synthesized product. Pore size distribution analyses revealed that the surfaces of the as-synthesized MgO have a slit-like pore structure with a broad-type pore size distribution, whereas the as-synthesized Mg(OH)2 has a mesoporous structure with a narrow pore size distribution. This structure enhances the latent heat of the phase change material (PCM) as well as super cooling mitigation. The PEG/Mg(OH)2 PCM also exhibits reproducible behavior over a large number of thermal cycles. Both MgO and Mg(OH)2 matrices prevent the leakage of liquid PEG during the phase transition in phase change materials (PCMs). However, MgO/PEG has a low impregnation ratio and efficiency, with a low thermal storage capability. This is due to the large pore diameter, which does not allow MgO to retain a larger amount of PEG. The latent heat values of PEG-1000/PEG-6000 blends with MgO and Mg(OH)2 were also determined with a view to extending the application of the PCMs to energy storage over wider temperature ranges.

Water-Erodible Xanthan-Acrylate-Polyurethane Antifouling Coating.

Biopolymer xanthan (Xn) and its functionalized polymer xanthan acrylate (XnAc) were used to improve the antifouling properties of synthesized waterborne polyurethane (WBPU) coatings, namely, WBPU-Xn and WBPU-XnAc. XnAc was synthesized by functionalization of xanthan (Xn) using polyacrylic acid. Coating hydrophilicity, adhesive strength, and erosion all varied with the Xn and XnAc contents. A moderate erosion rate was recorded only for the WBPU-XnAc coating. A good antifouling property for longer time was found in the WBPU-XnAc coating using zinc pyrithione as a biocide in the field test.

Host-Guest Extraction of Heavy Metal Ions with p-t-Butylcalix[8]arene from Ammonia or Amine Solutions.

The capacities of the p-t-butylcalix[8]arene (abbreviated as H8L) host to extract toxic divalent heavy metal ions and silver from aqueous solution phases containing ammonia or ethylene diamine to an organic phase (nitrobenzene, dichloromethane, or chloroform) were carried out. When the metal ions were extracted from an aqueous ammonia solution, the metal ion selectivity for extraction was found to decrease in the order Cd2+> Ni2+> Cu2+> Ag+> Co2+> Zn2+. When the aqueous phase contained ethylene diamine, excellent extraction efficiencies of 97% and 90% were observed for the heavy metal ions Cu2+ and Cd2+, respectively. Under the same conditions the extraction of octahedral type metal ions, namely, Co2+ and Ni2+, was suppressed. The extraction of transition metal cations by H8L in ammonia and/or amine was found to be pH dependent. Detailed analysis of extraction behavior was investigated by slope analysis, the continuous variation method, and by loading tests.

Modeling lead concentration in drinking water of residential plumbing pipes and hot water tanks.

Drinking water is a potential source of exposure to lead (Pb), which can pose risk to humans. The regulatory agencies often monitor Pb in water treatment plants (WTP) and/or water distribution systems (WDS). However, people are exposed to tap water inside the house while water may stay in the plumbing premise for several hours prior to reaching the tap. Depending on stagnation period and plumbing premise, concentrations of Pb in tap water can be significantly higher than the WDS leading to higher intake of Pb than the values from WDS or WTP. In this study, concentrations of Pb and water quality parameters were investigated in WDS, plumbing pipe (PP) and hot water tanks (HWT) for 7months. The samples were collected and analyzed on bi-weekly basis for 7 times a day. Several linear, non-linear and neural network models were developed for predicting Pb in PP and HWT. The models were validated using the additional data, which were not used for model development. The concentrations of Pb in PP and HWT were 1-1.17 and 1-1.21 times the Pb in WDS respectively. Concentrations of Pb were higher in summer than winter. The models showed moderate to excellent performance (R2=0.85-0.99) in predicting Pb in PP and HWT. The correlation coefficients (r) with the validation data were in the ranges of 0.76-0.90 and 0.97-0.99 for PP and HWT respectively. The models can be used for predicting Pb in tap water, which can assist to better protect the humans.

Synthesis and Properties of Waterborne Polyurethane (WBPU)/Modified Lignin Amine (MLA) Adhesive: A Promising Adhesive Material.

A series of waterborne polyurethane (WBPU)/modified lignin amine (MLA) adhesives was prepared using MLA as a chain extender by a prepolymer mixing process. A successful Mannich reaction was achieved during the synthesis of MLA by reacting lignin with bis(3-aminopropyl)amine. Higher tensile strength, Young's modulus, and thermal stability were recorded for WBPU/MLA adhesives with higher MLA contents. The WBPU/MLA adhesive materials were used to coat polyvinyl chloride (PVC) substrates. The adhesive strength increased with increasing MLA content. More importantly, the MLA also enhanced the WBPU/MLA coating in terms of adhesive strength at moderately high temperatures as well as under natural weather exposed conditions. The adhesive strength was essentially unaffected with 6.48 mol % MLA in the WBPU/MLA coating after exposure to natural weather conditions for 180 days.