Mesoporous Single Atom-Cluster Fe-N/C Oxygen Evolution Electrocatalysts Synthesized with Bottlebrush Block Copolymer-Templated Rapid Thermal Annealing.

Current electrocatalysts for oxygen evolution reaction (OER) are either expensive (such as IrO2, RuO2) or/and exhibit high overpotential as well as sluggish kinetics. This article reports mesoporous earth-abundant iron (Fe)-nitrogen (N) doped carbon electrocatalysts with iron clusters and closely surrounding Fe-N4 active sites. Unique to this work is that the mechanically stable mesoporous carbon-matrix structure (79 nm in pore size) with well-dispersed nitrogen-coordinated Fe single atom-cluster is synthesized via rapid thermal annealing (RTA) within only minutes using a self-assembled bottlebrush block copolymer (BBCP) melamine-formaldehyde resin composite template. The resulting porous structure and domain size can be tuned with the degree of polymerization of the BBCP backbone, which increases the electrochemically active surface area and improves electron transfer and mass transport for an effective OER process. The optimized electrocatalyst shows a required potential of 1.48 V (versus RHE) to obtain the current density of 10 mA/cm2 in 1 M KOH aqueous electrolyte and a small Tafel slope of 55 mV/decade at a given overpotential of 250 mV, which is significantly lower than recently reported earth-abundant electrocatalysts. Importantly, the Fe single-atom nitrogen coordination environment facilitates the surface reconstruction into a highly active oxyhydroxide under OER conditions, as revealed by X-ray photoelectron spectroscopy and in situ Raman spectroscopy, while the atomic clusters boost the single atoms reactive sites to prevent demetalation during the OER process. Density functional theory (DFT) calculations support that the iron nitrogen environment and reconstructed oxyhydroxides are electrocatalytically active sites as the kinetics barrier is largely reduced. This work has opened a new avenue for simple, rapid synthesis of inexpensive, earth-abundant, tailorable, mechanically stable, mesoporous carbon-coordinated single-atom electrocatalysts that can be used for renewable energy production.

Bacillus amyloliquefaciens AK-12 Helps Rapeseed Establish a Protection against Brevicoryne brassicae.

Aphids are a serious threat to rapeseed (Brassica napus L.) production, and cause unmanageable loss. Therefore, effective prevention and management strategies are urgently required to avoid losses. Bacillus amyloliquefaciens AK-12 isolated from a dead aphid with aphicidal activity was tagged with a green fluorescent protein through a natural transformation. The transformed strains were checked for stability and growth, and the best-performing strain was tested for its colonization inside and outside the rapeseed plant. The stability of AK-12-GFP reached more than 95%, and the growth curve was consistent with that of AK-12. After 30 days of treatment, the colonization of 1 × 106 CFU/g was recorded in rapeseed leaves. Interestingly, AK-12 reduced the aphid transmission rate compared with the control and improved the growth of the rapeseed seedlings. Meanwhile, the AK-12 strain also exhibited phosphorus, potassium-solubilizing, and nitrogen-fixing activity, and produced 2.61 µg/mL of IAA at 24 h. Regulation in the activity of four enzymes was detected after the AK-12 treatment. Phenylalanine ammonia lyase (PAL) was recorded at a maximum of 86.84 U/g after 36 h, and catalase (CAT) decreased after 48 h; however, peroxidase (POD) and polyphenol oxidase (PPO) reached the maximum within 12 h of AK-12 application. Additionally, important resistance genes related to these enzymes were upregulated, indicating the activation of a defense response in the rapeseed against aphids. In conclusion, defense enzymes and defense-related gene activation could improve the pest resistance in rapeseed, which has good application prospects for the future to be developed into biopesticide.

Enhancing the electrocatalytic activities of metal organic frameworks for the oxygen evolution reaction with bimetallic groups.

Controlling the ratio of metals in bimetallic organic frameworks (MOFs) can not only alter the structures but also tailor the properties of MOFs. Herein, we report a series of electrocatalytically active CoxNiy-based bimetallic MOFs that are synthesized with the 3,5-pyridinedicarboxylic acid (3,5-H2pdc) ligand (where x : y = 20 : 1, 15 : 1, 10 : 1, 5 : 1, 1 : 1, and 1 : 20) and a facile, scalable, low temperature synthetic route. The materials have one-dimensional (1D), rod-like microstructures with different aspect ratios. While they all electrocatalyze the oxygen evolution reaction (OER) in alkaline solution (1 M KOH), their electrocatalytic performances vary substantially depending on their compositions. The CoxNiy-MOF with an optimal ratio of x : y = 15 : 1 (Co15Ni1-MOF) electrocatalyzes the OER with the highest maximum current density (92.2 mA cm-2 at 1.75 V vs. RHE) and the smallest overpotential (384 mV vs. RHE at 10 mA cm-2) in a 1 M KOH solution. It is also stable under constant current application during the electrocatalytic OER. This work demonstrates the application of bimetallic MOFs that are synthesized following a simple, low temperature synthetic route for the OER and their tailorable electrocatalytic properties for the OER by varying the ratio of two metals and the synthetic conditions used to produce them.

Incorporation of Bismuth Increases the Electrocatalytic Activity of Cobalt Borates for Oxygen Evolution Reaction.

The development of durable and efficient electrocatalysts composed of low-cost, earth-abundant metals for the oxygen evolution reaction (OER) is crucial for industrial-scale water splitting to produce green hydrogen on a large scale. Transition metal borates are considered good candidate electrocatalysts for OER due to their low cost, ease of synthesis, and good catalytic activity. In this work, we demonstrate that the incorporation of an oxophilic main group metal, bismuth (Bi), into cobalt borates produces highly effective electrocatalysts for OER. We also show that the catalytic activity of Bi-doped cobalt borates can be improved further by pyrolyzing them in an argon atmosphere. During pyrolysis, the Bi crystallites formed in the materials melt, transform into amorphous phases, interact better with the Co or B atoms in there, and form more synergistic catalytic sites for OER. By varying the amount of Bi as well as the pyrolysis temperature, different Bi-doped cobalt borates are synthesized, and the most optimal OER electrocatalyst is identified. Among them, the one with Co : Bi ratio of 9 : 1 and that is pyrolyzed at 450 °C exhibits the best catalytic activity, driving the reaction at a current density of 10 mA cm-2 with the lowest overpotential (318 mV) and a Tafel slope of 37 mV dec-1 .

Repurposing Anthelmintics: Rafoxanide- and Copper-Functionalized SBA-15 Carriers against Methicillin-Resistant Staphylococcus aureus.

The development of materials that can more efficiently administer antimicrobial agents in a controlled manner is urgently needed due to the rise in microbial resistance to traditional antibiotics. While new classes of antibiotics are developed and put into widespread usage, existing, inexpensive compounds can be repurposed to fight bacterial infections. Here, we present the synthesis of amine-functionalized SBA-15 mesoporous silica nanomaterials with physisorbed rafoxanide (RFX), a commonly used salicylanilide anthelmintic, and anchored Cu(II) ions that exhibit enhanced antimicrobial efficacy against the pathogenic bacterium Staphylococcus aureus. The synthesized nanomaterials are structurally characterized by a combination of physicochemical, thermal, and optical methods. Additionally, release studies are carried out in vitro to determine the effects of pH and the synthetic sequence used to produce the materials on Cu(II) ion release. Our results indicate that SBA-15 mesoporous silica nanocarriers loaded with Cu(II) and RFX exhibit 10 times as much bactericidal action against wild-type S. aureus as the nanocarrier loaded with only RFX. Furthermore, the synthetic sequence used to produce the nanomaterials could significantly affect (enhance) their bactericidal efficacy.

Hierarchically Ordered Nanoporous Carbon with Exclusively Surface-Anchored Cobalt as Efficient Electrocatalyst.

A hierarchically ordered porous carbon electrocatalyst with exclusively surface-anchored cobalt species, dubbed Co@HOPC, is synthesized from polyaniline and cobalt-functionalized silica microparticles templates, and its high electrocatalytic activity for the oxygen evolution reaction (OER) is demonstrated. The material requires a small potential (320 mV) to drive the reaction with a current density of 10 mA cm-2 and a small Tafel slope of 31.2 mV dec-1 . Moreover, Co@HOPC shows better catalytic activity for OER than in situ cobalt-doped and surface cobalt-loaded hierarchically ordered porous carbon materials synthesized by traditional methods. This is due to the abundant surface cobalt species present in Co@HOPC and the material's good electrical conductivity. This work provides a new strategy to utilize functionalized silica microparticles as templates to synthesize hierarchically ordered porous carbon materials with metal-rich surfaces and efficient electrocatalytic activities.

Metal-Functionalized Hydrogels as Efficient Oxygen Evolution Electrocatalysts.

Conductive polymer hydrogels have large surface areas and electrical conductivities. Their properties can be further tailored by functionalizing them with metals and nonmetals. However, the potential applications of metal-functionalized hydrogels for electrocatalysis have rarely been investigated. In this work, we report the synthesis of transition-metal-functionalized polyaniline-phytic acid (PANI-PA) hydrogels that show efficient electrocatalytic activities for the oxygen evolution reaction (OER). Among the many transition metals studied, Fe is accommodated by the hydrogel the most due to the favorable affinity of the PA groups in the hydrogel for Fe. Meanwhile, those containing both Fe and Co are found to be the most effective electrocatalysts for OER. The most optimized such hydrogel, NF@Hgel-Fe0.3Co0.1, which is made using a solution that has a 3:1 ratio of Fe and Co, needs an overpotential of only 280 mV to catalyze OER in 1 M KOH solution with a current density of 10 mV cm-2. Furthermore, these metal-functionalized PANI-PA hydrogels can easily be loaded on the nickel foam or carbon cloth via a simple soak-and-dry method to generate free-standing electrodes. Overall, this work demonstrates a facile synthesis and fabrication of sustainable and efficient OER electrocatalysts and electrodes that are composed of easily processable hydrogels functionalized with earth-abundant transition metals.

Nanostructured Carbon Electrocatalysts for Energy Conversions.

The growing energy demand worldwide has led to increased use of fossil fuels. This, in turn, is making fossil fuels dwindle faster and cause more negative environmental impacts. Thus, alternative, environmentally friendly energy sources such as fuel cells and electrolyzers are being developed. While significant progress has already been made in this area, such energy systems are still hard to scale up because of their noble metal catalysts. In this concept paper, first, various scalable nanocarbon-based electrocatalysts that are being synthesized for energy conversions in these energy systems are introduced. Next, notable heteroatom-doping and nanostructuring strategies that are applied to produce different nanostructured carbon materials with high electrocatalytic activities for energy conversions are discussed. The concepts used to develop such materials with different structures and large density of dopant-based catalytic functional groups in a sustainable way, and the challenges therein, are emphasized in the discussions. The discussions also include the importance of various analytical, theoretical, and computational methods to probe the relationships between the compositions, structures, dopants, and active catalytic sites in such materials. These studies, coupled with experimental studies, can further guide innovative synthetic routes to efficient nanostructured carbon electrocatalysts for practical, large-scale energy conversion applications.