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As more than 60% of worldwide consumed energy is unused and becomes waste heat every year, high-efficiency waste heat to power technologies are highly demanded for the conversion of wasted heat to electricity. Thermoelectrics which can convert the wasted heat directly into electricity represent a promising approach for energy recovery. Thermoelectric technology has existed for several decades, but its usage has been limited due to low efficiencies. Recent advances in nanotechnology have enabled the improving of thermoelectric properties which open up the thermoelectrics’ feasibility in industry. In this paper, we present an overview of recent progress in increasing the porosity of thermoelectric materials from atomic scale to microscale, leading to the enhancement of figure of merit.

The development of cost-effective electrocatalysts for overall water splitting is highly desirable, remaining a critical challenge at current stage. Herein, a class of composite FeNi@MXene (Mo 2 TiC 2 T x )@nickel foam (NF) has been synthesized through introducing Fe 2+ ions and in-situ combining with surface nickel atoms on nickel foam. The obtained FeNi@Mo 2 TiC 2 T x @NF exhibited high activity with overpotentials of 165 and 190 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a current density of 10 mA·cm −2 , respectively. The synergetic effects of Mo 2 TiC 2 T x and FeNi nanoalloys lead to increasing catalytic activities, where MXene provides high active surface area and rich active sites for HER, and FeNi nanoalloys promote the OER. Theoretical simulation of electron exchange capacity between FeNi and MXene in FeNi@Mo 2 TiC 2 T x catalyst shows that electrons transferred from surface Mo atoms to the interface between FeNi and MXene, indicating that the electrons are accumulated near the FeNi nanoparticles. This kind of electronic distribution facilitates the formation of intermediate of NiOOH. Correspondingly, (H + + e − ) is more inclined onto Mo-Ni interfaces for HER. The Gibbs free energy changes for H* to HER and potential-limiting step for −OOH intermediate in OER over FeNi@Mo 2 TiC 2 T x are much less than those on bare MXene. The catalyst can be further used for overall water splitting in alkaline solution, realizing a current density of 50 mA·cm −2 at 1.74 V. This work provides a facile strategy to achieve efficient and cheap catalysts for new energy production.

Efficient and direct conversion of methane to value-added products has been a long-term challenge in shale gas applications. Here, we show that atomically thin nanolayers of Pt with a single or double atomic layer thickness, supported on a two-dimensional molybdenum titanium carbide (MXene), catalyse non-oxidative coupling of methane to ethane/ethylene (C 2 ). Kinetic and theoretical studies, combined with in-situ spectroscopic and microscopic characterizations, demonstrate that Pt nanolayers anchored at the hexagonal close-packed sites of the MXene support can activate the first C–H bond of methane to form methyl radicals that favour desorption over further dehydrogenation and thus suppress coke deposition. At 750 °C and 7% methane conversion, the catalyst runs for 72 hours of continuous operation without deactivation and exhibits >98% selectivity towards C 2 products, with a turnover frequency of 0.2–0.6 s −1 . Our findings provide insights into the design of highly active and stable catalysts for methane activation and create a platform for developing atomically thin supported metal catalysts. The challenge in non-oxidative coupling of methane lies in the activation of the first C–H bond while avoiding further dehydrogenations, which lead to the formation of coke. Here, atomically thin platinum nanolayers on two-dimensional molybdenum titanium carbides are reported as a superior catalyst for this reaction owing to reduced coke formation.

The preparation of a high performance and durability with low-platinum (Pt) loading oxygen reduction catalysts remains a challenge for the practical application of fuel cells. Alloying Pt with a transition metal can greatly improve the activity and durability for oxygen reduction reaction (ORR). In this work, we present a one-pot wet-chemical strategy to controllably synthesize carbon supported sub-5 nm PtNi nanocrystals with a ~3% Pt loading. The as-prepared PtNi/C-200 catalyst with a Pt/Ni atomic ratio of 2:3 shows a high oxygen reduction activity of 0.66 A mgpt−1 and outstanding durability over 10,000 potential cycles in 0.1 M KOH in a half-cell condition. The PtNi/C-200 catalyst exhibits the highest ORR activity, with an onset potential (Eonset) of 0.98 V and a half-wave potential (E1/2) of 0.84 V. The mass activity and specific activity are 3.89 times and 9.16 times those of 5% commercial Pt/C. More importantly, this strategy can be applied to the gram-scale synthesis of high-efficiency electrocatalysts. As a result, this effective synthesis strategy has a significant meaning in practical applications of full cells.

Covalent organic frameworks (COFs)-based nanoreactors have attracted broad interest in many fields due to their void-confinement effects. However, the inherent drawback of conventional nanoreactors is the lack of internal active sites, which limits their widespread utilization. Herein, we report the construction of hierarchical COF (EB-TFP) nanoreactor with pre-synthesized polyoxometalates (POM, [PV 2 W 10 O 40 ] 5− (PV 2 W 10 )) clusters encapsulated inside of COF (POM@COF). PV 2 W 10 @EB-TFP anchors nucleophilic-group (Br − ions) and PV 2 W 10 anion cluster within the COF framework via electrostatic interactions, which not only simplifies the reaction system but also enhances catalytic efficiency. The reaction performance of the PV 2 W 10 @EB-TFP nanoreactor can be tuned to achieve excellent catalytic activity in CO 2 cycloaddition reaction (CCR) for ∼ 97.63% conversion and ∼ 100% selectivity under visible light irradiation. A mechanistic study based on density functional theory (DFT) calculations and in-situ characterization was also carried out. In summary, we have reported a method for achieving the uniform dispersion of POM single clusters into COF nanoreactor, demonstrating the potential of POM@COF nanoreactor for synergistic photothermal catalytic CO 2 cycloaddition.

It is significant to develop highly efficient electrocatalysts for energy conversion systems. Interface engineering is one of the most feasible approaches to effectively enhance the electrocatalytic activity. Herein, the density functional theory (DFT) calculations predict that the potential barriers of Fe sites at the interface of FeP—CoP heterostructures are lower than that of Fe sites in FeP nanoparticles (NPs), Co sites in CoP NPs, or Co sites in heterostructures. Motivated by the DFT calculation results, FeP—CoP heterostructures have been designed and synthesized by a metal—organic frameworks (MOFs) confined-phosphorization method. The FeP—CoP exhibits the lowest overpotential of 230 mV at the current density of 10 mA·cm −2 for oxygen evolution reaction (OER), compared with FeP (470 mV) and CoP (340 mV), which outperforms most of transition metal-based catalysts. The Tafel analysis of FeP—CoP heterostructures shows an improved reaction kinetic pathway with the smallest slope of 90.3 mV·dec − 1 , as compared to the Tafel slopes of FeP NPs (137 mV·dec − 1 ) and CoP NPs (114 mV·dec − 1 ). And the FeP—CoP shows extraordinary long-term stability over 24 h. The excellent activity and long-term stability of FeP—CoP derive from the synergistic effect between FeP and CoP.

It is important and challenging to analyze nanocluster structure with atomic precision. Herein, α-hemolysin nanopore was used to identify nanoclusters at the single molecule level by providing two-dimensional (2D) dwell time–current blockage spectra and translocation event frequency which sensitively depended on their structures. Nanoclusters such as Anderson, Keggin, Dawson, and a few lacunary Dawson polyoxometalates with very similar structures, even with only a two-atom difference, could be discriminated. This nanopore device could simultaneously measure multiple nanoclusters in a mixture qualitatively and quantitatively. Furthermore, molecular dynamics (MD) simulations provided microscopic understandings of the nanocluster translocation dynamics and yielded 2D dwell time–current blockage spectra in close agreement with experiments. The nanopore platform provides a novel powerful tool for nanocluster characterization.

Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing.

Background Due to drought stress, the growth, distribution, and production of mungbean is severely restricted. Previous study combining physiological and transcriptomic data indicated different genotypes of mungbean exhibited variable responses when exposed to drought stress. Aside from the genetic variation, the modifications of environmentally induced epigenetics alterations on mungbean drought-stress responses were still elusive. Results In this study, firstly, we compared the drought tolerance capacity at seedling stage by detecting physiological parameters in two contrasting genotypes wild mungbean 61 and cultivar 70 in response to drought stress. We found that wild mungbean 61 showed lower level of MDA and higher levels of POD and CAT, suggesting wild mungbean 61 exhibited stronger drought resistance. Transcriptomic analysis indicated totally 2859 differentially expressed genes (DEGs) were detected when 70 compared with 61 (C70 vs C61), and the number increased to 3121 in the comparison of drought-treated 70 compared with drought-treated 61 (D70 vs D61). In addition, when drought-treated 61 and 70 were compared with their controls, the DEGs were 1117 and 185 respectively, with more down-regulated DEGs than up-regulated in D61 vs C61, which was opposite in D70 vs C70. Interestingly, corresponding to this, after drought stress, more hypermethylated differentially methylated regions (DMRs) in 61 were detected and more hypomethylated DMRs in 70 were detected. Further analysis suggested that the main variations between 61 and 70 existed in CHH methylation in promoter. Moreover, the preference of methylation status alterations in D61 vs C61 and D70 vs C70 also fell in CHH sequence context. Further analysis of the correlation between DMRs and DEGs indicated in both D61 vs C61 and D70 vs C70, the DMRs in gene body was significantly negatively correlated with DEGs. Conclusions The physiological parameters in this research suggested that wild mungbean 61 was more resistant to drought stress, with more hypermethylated DMRs and less hypomethylated DMRs after drought stress, corresponding to more down-regulated DEGs than up-regulated DEGs. Among the three DNA methylation contexts CG, CHG, and CHH, asymmetric CHH contexts were more dynamic and prone to be altered by drought stress and genotypic variations.