Electrocatalytic Oxygen Reduction Performance of Silver Nanoparticle Decorated Electrochemically Exfoliated Graphene

Appraising the potency of small molecule inhibitors and their graphene surface-mediated organizational attributes on uric acid-melamine clusters

Uric acid (UA) and melamine (MM) crystallization in humans is associated with adverse medical conditions, including the germination of kidney stones, because of their low solubility. The growth of kidney stones, usually formed on renal papillary facades, is accomplished on the matrix-coated surface by the aggregation of preformed crystals or secondary crystal nucleation. Therefore, the effects of inhibitors such as theobromine (TB) and allopurinol (AP) on MM-UA aggregation are investigated by employing classical molecular dynamics simulations on a graphene surface. This impersonates the exact essence of the precipitation of kidney stones. The interaction between MM-UA is very intense and, thus, large clusters are formed on the surface. The presence of TB and AP will, however, substantially inhibit their aggregation. TB and AP significantly impede UA aggregation in particular. Therefore, lower order UA clusters are formed. These smaller UA clusters then pull a lower number of MM towards themselves, resulting in a smaller order UA-MM cluster. MM and UA aggregation on a 2D graphene surface is found to be spontaneous. There is no difference in these molecules' adsorption with a change in the force field parameters (i.e., GAFF and OPLS-AA) for graphene. Moreover, the greater the surface area of graphene, the more molecules are absorbed. The solute-surface van der Waals interaction energy plays a driving force in the adsorption of solute molecules on the surface. In addition, interactions like hydrogen bonding and π-stacking over the graphene surface involve binding all like molecules. These aggregated solute molecules strongly attract more like molecules until all solute molecules are adsorbed on the graphene surface, as estimated by enhanced sampling. The molecular origin of graphene exfoliation by MM is also described here. The present work helps to design novel kidney stone inhibitors.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

A No-Sweat Strategy for Graphene-Macrocycle Co-assembled Electrocatalyst toward Oxygen Reduction and Ambient Ammonia Synthesis

Toward the realm of sustainable energy, the development of efficient methods to enhance the performance of electrocatalysts with molecular level perception has gained immense attention. Inspite of untiring attempts, the production cost and scaling-up issues have been a step back toward the commercialization of the electrocatalysts. Herein, we report a one-pot electrophoretic exfoliation technique with minimum time and power input to synthesize iron phthalocyanine functionalized high-quality graphene sheets (G-FePc). The π-stacked co-assembly excels in oxygen reduction performance (major criterion for fuel cells) with a high positive E_1/2 of 0.91 V (vs RHE) and a reproducible reduction peak potential of 0.90 V (vs RHE). An overpotential as low as 29 mV dec^-1 and complete tolerance toward the methanol crossover effect confirm the authentication of the catalytic performance of our designed catalyst G-FePc. The catalyst simultaneously exhibits hydrogen storage efficacy by means of nitrogen fixation, yielding 27.74 μg h^-1 mg_cat^-1 NH₃ at a potential of -0.3 V (vs RHE) in an acidic electrolyte. The structure-function relationship of the catalyst is revealed via molecular orbital chemistry for the bonding of the Fe(II) active center with O₂ and N₂ during catalysis.

Electroceutical Silk-Silver Gel to Eradicate Bacterial Infection

With more than 50% of bacteria resistant to standard antibiotics, new strategies to treat bacterial infection and colonization are needed. Based on the concept of targeting the bacteria synergistically on various fronts, it is hypothesized that an electrical insult associated with antibacterial materials may be a highly effective means of killing bacteria. In this work, an injectable conductive gel based on silk fibroin (SF) and silver nanoparticles (Ag-NPs) is synthesized, capable of coating a zone of injury, allowing the application of a low electrical current to decrease bacterial contamination. With a high conductivity of 1.5 S cm^-1 , SF/Ag-NPs gels killed 80% of Escherichia coli in 1 min, no toxicity toward Chinese hamster ovary cells is observed. The mechanism of an electrical composite gel combined with electrical wound therapy is associated with silver ion (Ag⁺ ) release, and reactive oxygen species (ROS) production. The findings in the present study show a similar Ag⁺ release for treatment with gels and the combined effect, whereas ROS generation is 50% higher when a small electrical current is applied leading to a broad bactericidal effect.

Plasmonic-Enhanced Oxygen Reduction Reaction of Silver/Graphene Electrocatalysts

Oxygen reduction reaction (ORR) is of paramount importance in polymer electrolyte membrane fuel cells due to its sluggish kinetics. In this work, a plasmon-induced hot electrons enhancement method is introduced to enhance ORR property of the silver (Ag)-based electrocatalysts. Three types of Ag nanostructures with differently localized surface plasmon resonances have been used as electrocatalysts. The thermal effect of plasmonic-enhanced ORR can be minimized in our work by using graphene as the support of Ag nanoparticles. By tuning the resonance positions and laser power, the enhancement of ORR properties of Ag catalysts has been optimized. Among these catalysts, Ag nanotriangles after excitation show the highest mass activity and reach 0.086 mA/μg_Ag at 0.8 V, which is almost 17 times that of a commercial Pt/C catalyst after the price is accounted. Our results demonstrate that the hot electrons generated from surface plasmon resonance can be utilized for electrochemical reaction, and tuning the resonance positions by light is a promising and viable approach to boost electrochemical reactions.

P. Oliveira R, Stoševski I, Krstić J, Hercigonja R, Miljanić Š, Santos DMF, Šljukić B. Evaluation of silver-incorporating zeolites as bifunctional electrocatalysts for direct borohydride fuel cells

Low cost zeolites with incorporated silver show high activity for both oxygen reduction and borohydride oxidation reaction.

New-Generation Graphene from Electrochemical Approaches: Production and Applications

Extensive research suggests a bright future for the graphene market. However, for a long time there has been a huge gap between laboratory-scale research and commercial application due to the challenging task of reproducible bulk production of high-quality graphene at low cost. Electrochemical exfoliation of graphite has emerged as a promising wet chemical method with advantages such as upscalability, solution processability and eco-friendliness. Recent progress in the electrochemical exfoliation of graphite and prospects for the application of exfoliated graphene, mainly in the fields of composites, electronics, energy storage and conversion are discussed.

In situ growth of silver nanowires on reduced graphene oxide sheets for transparent electrically conductive films

In situ growth of silver nanowires (AgNWs) on the surface of functionalized-graphene (rGO) nanosheets is achieved and highly transparent, flexible and conductive AgNW–rGO/PVA films could be fabricated.