Wood-inspired metamaterial catalyst for robust and high-throughput water purification.

Continuous industrialization and other human activities have led to severe water quality deterioration by harmful pollutants. Achieving robust and high-throughput water purification is challenging due to the coupling between mechanical strength, mass transportation and catalytic efficiency. Here, a structure-function integrated system is developed by Douglas fir wood-inspired metamaterial catalysts featuring overlapping microlattices with bimodal pores to decouple the mechanical, transport and catalytic performances. The metamaterial catalyst is prepared by metal 3D printing (316 L stainless steel, mainly Fe) and electrochemically decorated with Co to further boost catalytic functionality. Combining the flexibility of 3D printing and theoretical simulation, the metamaterial catalyst demonstrates a wide range of mechanical-transport-catalysis capabilities while a 70% overlap rate has 3X more strength and surface area per unit volume, and 4X normalized reaction kinetics than those of traditional microlattices. This work demonstrates the rational and harmonious integration of structural and functional design in robust and high throughput water purification, and can inspire the development of various flow catalysts, flow batteries, and functional 3D-printed materials.

Twinning Engineering of Platinum/Iridium Nanonets as Turing-Type Catalysts for Efficient Water Splitting.

The twin boundary, a common lattice plane of mirror-symmetric crystals, may have high reactivity due to special atomic coordination. However, twinning platinum and iridium nanocatalysts are grand challenges due to the high stacking fault energies that are nearly 1 order of magnitude larger than those of easy-twinning gold and silver. Here, we demonstrate that Turing structuring, realized by selective etching of superthin metal film, provides 14.3 and 18.9 times increases in twin-boundary densities for platinum and iridium nanonets, comparable to the highly twinned silver nanocatalysts. The Turing configurations with abundant low-coordination atoms contribute to the formation of nanotwins and create a large active surface area. Theoretical calculations reveal that the specific atom arrangement on the twin boundary changes the electronic structure and reduces the energy barrier of water dissociation. The optimal Turing-type platinum nanonets demonstrated excellent hydrogen-evolution-reaction performance with a 25.6 mV overpotential at 10.0 mA·cm-2 and a 14.8-fold increase in mass activity. And the bifunctional Turing iridium catalysts integrated in the water electrolyzer had a mass activity 23.0 times that of commercial iridium catalysts. This work opens a new avenue for nanocrystal twinning as a facile paradigm for designing high-performance nanocatalysts.

Turing structuring with multiple nanotwins to engineer efficient and stable catalysts for hydrogen evolution reaction.

Low-dimensional nanocrystals with controllable defects or strain modifications are newly emerging active electrocatalysts for hydrogen-energy conversion and utilization; however, a crucial challenge remains in insufficient stability due to spontaneous structural degradation and strain relaxation. Here we report a Turing structuring strategy to activate and stabilize superthin metal nanosheets by incorporating high-density nanotwins. Turing configuration, realized by constrained orientation attachment of nanograins, yields intrinsically stable nanotwin network and straining effects, which synergistically reduce the energy barrier of water dissociation and optimize the hydrogen adsorption free energy for hydrogen evolution reaction. Turing PtNiNb nanocatalyst achieves 23.5 and 3.1 times increase in mass activity and stability index, respectively, compared against commercial 20% Pt/C. The Turing PtNiNb-based anion-exchange-membrane water electrolyser with a low Pt mass loading of 0.05 mg cm-2 demonstrates at least 500 h stability at 1000 mA cm-2, disclosing the stable catalysis. Besides, this new paradigm can be extended to Ir/Pd/Ag-based nanocatalysts, illustrating the universality of Turing-type catalysts.

PEG-functionalized black phosphorus quantum dots as stable and biocompatible electrochemiluminescence luminophores for sensitive detection of tumor biomarker.

Despite black phosphorous (BP) QDs possess the merits of size-tunable band-gap, high electron mobility, and intrinsic defects, the spontaneous agglomeration and rapid oxidation of BP QDs in aqueous solution caused low electrochemiluminescence (ECL) efficiency and unstable ECL signal, which confined its further application of biological analysis. Herein, polyethylene glycol-functionalized BP QDs (PEG@BP QDs) were prepared showing an efficient and stable ECL response, which is attributed to the fact that PEG as protectant not only effectively prevented the spontaneous agglomeration, but also restrained the rapid oxidation of BP QDs in aqueous solution. As proof-of-concept, PEG@BP QDs were used as an efficient ECL emitter to combine with palindrome amplification-induced DNA walker to construct a sensitive ECL aptasensing platform for detecting cancer marker mucin 1 (MUC1). Interestingly, with the aid of positively charged thiolated PEG, the reaction rate of DNA walker on the electrode interface was clearly increased for the recovery of the ECL signal. The ECL aptasensor provides sensitive determination with the detection limit of 16.5 fg/mL. The proposed strategy paves a path for the development of efficient and stable ECL nanomaterials to construct biosensors for biosensing and clinical diagnosis.

Does the aging behavior of microplastics affect the process of denitrification by the difference of copper ion adsorption?

Riparian sediment is a hot zone for denitrification that can withhold copper and microplastics (MPs) from outside. It has been proven that MPs affect denitrification and the existing forms of copper in the environment. However, the impact of copper on sediment denitrification under exposure to MPs remains unclear. This study revealed the response of sediment denitrification to copper availability under the adsorption of MPs and the complexation of MP-derived dissolved organic matter (DOM). These results showed that MP accumulation inhibited denitrification. However, aged MPs increased the activity of nitrite reductase (12.64%), nitrogen dioxide reductase (37.68%), and electron transport (28.93%) compared with pristine MPs. The aging behavior of MPs alleviated 28.18% nitrite accumulation and 16.41-118.35% nitrous oxide emissions. Thus, the aging behavior of MPs alleviated the inhibition of denitrification. Notably, we resolved the copper ion adsorption and complexation by MPs, MP-derived DOM contributed to the denitrification process, and we found that the key nitrogen removal factors were affected by KL, KM, and K2. These results fill a gap in our understanding of biochemical synthesis of MPs during denitrification. Furthermore, it can be used to build a predictive understanding of the long-term effects of MPs on the sediment nitrogen cycle.

Which sediment fraction mainly drives microplastics aging process: Dissolved organic matter or colloids?

Riparian sediment is the last barrier preventing contaminants from polluting aquatic ecosystems. Recently, microplastics (MPs) have frequently been found in sediments. However, the MP aging process and its impact on sediments remain unknown. This study aimed to identify the key driving factors and mechanisms of riparian sediment on MPs aging behavior. The results showed that MPs surface suffered heavy breakage and the oxygen-to-carbon ratio of MPs increased by 268 % after accumulation in sediment for 214 d. The carbonyl index revealed that the degree of MP aging driven by dissolved organic matter (DOM) was 6.7-83.6 % greater than that of colloids, indicating that DOM was the key sediment fraction driving MP aging. Sunlight was an important environmental factor that enhanced MPs aging by sediment fractions, because photo-irradiated DOM produced hydroxyl and superoxide radicals to damage the MPs structure. Benzoic acid, dibenzoylmethane, and 4-heptyl-4,6-diphenyl-tetrahydro-pytan-2-one were the main products during the MP aging process under the interaction of sunlight and DOM, which showed acute toxicity to aquatic organisms and caused more severe toxicity during the chronic period. These results clearly clarify the behavior and environmental risk of MPs after accumulation in sediment, providing guide information to control MP pollution in the riparian zone.

A crystal glass-nanostructured Al-based electrocatalyst for hydrogen evolution reaction.

Platinum-based catalysts are widely used in hydrogen evolution reactions; however, their applications are restricted because of the cost-efficiency trade-off. Here, we present a thermodynamics-based design strategy for synthesizing an Al73Mn7Ru20 (atomic %) metal catalyst via combinatorial magnetron co-sputtering. The new electrocatalyst is composed of ~2 nanometers of medium-entropy nanocrystals surrounded by ~2 nanometers of amorphous regions. The catalyst exhibits exceptional performance, similar to that of single-atom catalysts and better than that of nanocluster-based catalysts. We use aluminum rather than a noble metal as the principal element of the catalyst and ruthenium, which is cheaper than platinum, as the noble metal component. The design strategy provides an efficient route for the development of electrocatalysts for use in large-scale hydrogen production. Moreover, the superior hydrogen reaction evolution created by the synergistic effect of the nano-dual-phase structure is expected to guide the development of high-performance catalysts in other alloy systems.

Evaluation of different deep convolutional neural networks for detection of broadleaf weed seedlings in wheat.

BACKGROUND: In-field weed detection in wheat (Triticum aestivum L.) is challenging due to the occurrence of weeds in close proximity with the crop. The objective of this research was to evaluate the feasibility of using deep convolutional neural networks for detecting broadleaf weed seedlings growing in wheat. RESULTS: The object detection neural networks, including CenterNet, Faster R-CNN, TridenNet, VFNet, and You Only Look Once Version 3 (YOLOv3) were insufficient for weed detection in wheat because the recall never exceeded 0.58 in the testing dataset. The image classification neural networks including AlexNet, DenseNet, ResNet, and VGGNet were trained with small (5500 negative and 5500 positive images) or large training datasets (11 000 negative and 11 000 positive images) and three training image sizes (200 × 200, 300 × 300, and 400 × 400 pixels). For the small training dataset, increasing image sizes decreased the F1 scores of AlexNet and VGGNet but generally increased the F1 scores of DenseNet and ResNet. For the large training dataset, no obvious difference was detected between the training image sizes since all neural networks exhibited remarkable classification accuracies with high F1 scores (≥0.96). All image classification neural networks exhibited high F1 scores (≥0.99) when trained with the large training dataset and the training images of 200 × 200 pixels. CONCLUSION: CenterNet, Faster R-CNN, TridentNet, VFNet, and YOLOv3 were insufficient, while AlexNet, DenseNet, ResNet, and VGGNet trained with a large training dataset were highly effective for detection of broadleaf weed seedlings in wheat. © 2021 Society of Chemical Industry.

All-solid-state bipolar pulsed generator based on linear transformer driver and push-pull circuit.

All-solid-state linear transformer drivers (LTDs) are widely used in high-voltage repetitive nanosecond-pulsed generators, and only a few LTD generators can output bipolar rectangular waves currently. Furthermore, owing to the large reverse overshoot when the output pulse width is long, fewer LTD generators can achieve a rectangular wave output with a microsecond pulse width. In this study, a bipolar LTD circuit topology based on a push-pull circuit is proposed for irreversible electroporation. In this topology, a single-stage LTD module has four push-pull branches in its primary winding to achieve a bipolar output and a short-circuited winding with two resistor-capacitor-diode snubbers to suppress forward/reverse overshoot. A single-stage LTD module and a 12-stage LTD have been tested, and the results show that they can output bipolar rectangular pulses with variable parameters. When the output pulse width is 100 ns to 1 µs, the maximum output voltage amplitude is 5.74 kV, the rise time is 29.1 ns, and the reverse overshoot at 1 µs is 2.9%. When the output pulse width is 1-8 µs, the maximum output voltage amplitude is 2.93 kV, the rise time is 24.3 ns, and the reverse overshoot at 8 µs is 11.3%.

A Tensile-Strained Pt-Rh Single-Atom Alloy Remarkably Boosts Ethanol Oxidation.

The rational design and control of electrocatalysts at single-atomic sites could enable unprecedented atomic utilization and catalytic properties, yet it remains challenging in multimetallic alloys. Herein, the first example of isolated Rh atoms on ordered PtBi nanoplates (PtBi-Rh1 ) by atomic galvanic replacement, and their subsequent transformation into a tensile-strained Pt-Rh single-atom alloy (PtBi@PtRh1 ) via electrochemical dealloying are presented. Benefiting from the Rh1 -tailored Pt (110) surface with tensile strain, the PtBi@PtRh1 nanoplates exhibit record-high and all-round superior electrocatalytic performance including activity, selectivity, stability, and anti-poisoning ability toward ethanol oxidation in alkaline electrolytes. Density functional theory calculations reveal the synergism between effective Rh1 and tensile strain in boosting the adsorption of ethanol and key surface intermediates and the CC bond cleavage of the intermediates. The facile synthesis of the tensile-strained single-atom alloy provides a novel strategy to construct model nanostructures, accelerating the development of highly efficient electrocatalysts.

Novel Bi-Doped Amorphous SnOx Nanoshells for Efficient Electrochemical CO2 Reduction into Formate at Low Overpotentials.

Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1- x Bix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (-0.67 to -0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80 Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm-2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO.

Trimetallic Synergy in Intermetallic PtSnBi Nanoplates Boosts Formic Acid Oxidation.

Platinum is the most effective metal for a wide range of catalysis reactions, but it fails in the formic acid electrooxidation test and suffers from severe carbon monoxide poisoning. Developing highly active and stable catalysts that are capable of oxidizing HCOOH directly into CO2 remains challenging for commercialization of direct liquid fuel cells. A new class of PtSnBi intermetallic nanoplates is synthesized to boost formic acid oxidation, which greatly outperforms binary PtSn and PtBi intermetallic, benefiting from the synergism of chosen three metals. In particular, the best catalyst, atomically ordered Pt45 Sn25 Bi30 nanoplates, exhibits an ultrahigh mass activity of 4394 mA mg-1 Pt and preserves 78% of the initial activity after 4000 potential cycles, which make it a state-of-the-art catalyst toward formic acid oxidation. Density functional theory calculations reveal that the electronic and geometric effects in PtSnBi intermetallic nanoplates help suppress CO* formation and optimize dehydrogenation steps.