Single-atom electrocatalysts (SAEs) can realize the target of low-cost by maximum atomic efficiency. However, they usually suffer performance decay due to high energy states, especially in a harsh ...acidic water splitting environment. Here, we conceive and realize a double protecting strategy that ensures robust acidic water splitting on Ir SAEs by dispersing Ir atoms in/onto Fe nanoparticles and embedding IrFe nanoparticles into nitrogen-doped carbon nanotubes (Ir-SA@Fe@NCNT). When Ir-SA@Fe@NCNT acts as a bifunctional electrocatalyst at ultralow Ir loading of 1.14 μg cm–2, the required overpotentials to deliver 10 mA cm–2 are 250 and 26 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 0.5 M H2SO4 electrolyte corresponding to 1370- and 61-fold better mass activities than benchmark IrO2 and Pt/C at an overpotential of 270 mV, respectively, resulting in only 1.51 V to drive overall water splitting. Moreover, remarkable stability is also observed compared to Pt/C-IrO2.
Highlights
Secondary-atom-doped strategy was proposed to synthesize single-atom electrocatalyst.
The increase in both the density of active sites and their intrinsic activity was achieved ...simultaneously.
The resultant single-atom catalyst shows outstanding ORR activity in acidic media.
Single-atom catalysts (SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis. However, a large room for improving their activity and durability remains. Herein, we construct atomically dispersed Fe sites in N-doped carbon supports by secondary-atom-doped strategy. Upon the secondary doping, the density and coordination environment of active sites can be efficiently tuned, enabling the simultaneous improvement in the number and reactivity of the active site. Besides, structure optimizations in terms of the enlarged surface area and improved hydrophilicity can be achieved simultaneously. Due to the beneficial microstructure and abundant highly active FeN
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moieties resulting from the secondary doping, the resultant catalyst exhibits an admirable half-wave potential of 0.81 V versus 0.83 V for Pt/C and much better stability than Pt/C in acidic media. This work would offer a general strategy for the design and preparation of highly active SACs for electrochemical energy devices.
A gold-catalyzed cascade reaction of skipped diynes (1,4-diynes) and pyrroles has been developed. This reaction proceeds by the consecutive regioselective hydroarylation of two alkynes with a ...pyrrole, followed by a 7-endo-dig cyclization to give 1,6-dihydrocycloheptabpyrroles in good yields. The direct synthesis of cycloheptabindoles using indole nucleophiles has also been reported.
We recently reported that the combination of the neutrophil-to-lymphocyte ratio (NLR) and the platelet-to-lymphocyte ratio (PLR) is a novel and useful predictor of intravenous immunoglobulin ...(IVIG)-resistance in Kawasaki disease (KD). In the present study, to evaluate the effectiveness of the new risk score, we compared its predictive validity to that of previously reported risk scores.
The laboratory records of 437 patients with KD before IVIG therapy were retrospectively analyzed, and the IVIG-responsive (n = 344) and IVIG-resistant (n = 93) patients were compared. The validity of the new score (the combination of NLR≥3.83 and PLR≥150) for predicting IVIG resistance in KD was compared to that of the Kobayashi, Egami and Sano risk scores.
The new score and the Kobayashi score displayed high sensitivity (0.72 and 0.70 respectively) and specificity (0.67 and 0.68 respectively), while the Egami and Sano scores showed high specificity (0.71 and 0.81 respectively) but relatively low sensitivity (0.56 and 0.45 respectively). The odds ratios (ORs) for the new score, the Kobayashi score, the Egami score and the Sano score were 5.34 (95% confidence interval CI 3.22-8.85), 4.87 (95% CI 2.96-8.01), 3.14 (95% CI 1.96-5.03) and 3.53 (95% CI 2.17-5.77) respectively.
The predictive validity of the combination of NLR≥3.83 and PLR≥150, which is a simple and convenient indicator, was equal to or higher than that of the other risk scores. This suggests that the new score could be a widely available marker for predicting IVIG resistance in KD.
•Assemblies of layered double hydroxide with Ag or Au nanoparticles were prepared.•Assemblies with Ag/Au via LDH reconstruction were compared to that via ion exchange.•Surface plasmon resonance of Ag ...enhanced the CO2 photoreduction on LDH to CH3OH/CO.•Au promoted the CO2 photoreduction on LDH but switched to CO selective.•Au worked as electron trap due to greater work function and the SPR did not work.
In the search for novel efficient photocatalysts for the conversion of CO2 into fuels, plasmonic photocatalysts based on the self-assemblies of silver or gold nanoparticles with Zn3Ga(OH)82CO3·mH2O layered double hydroxide (Zn3Ga|CO3 LDH) were prepared and tested for the photoreduction of CO2 by H2 under irradiation with UV–visible light. Ag and Au nanoparticles were obtained directly on the LDHs via the ion-exchange method or the reconstruction method of the LDHs. The catalysts exhibited intense surface plasmon resonance (SPR) effect at 411 and 555nm attributable to Ag and Au nanoparticles, respectively. The rate of CO2 photoreduction on Ag/Zn3Ga|CO3 increased by a factor of 1.69 than that of Zn3Ga|CO3 while the methanol selectivity also increased from 39 to 54mol%. On Au/Zn3Ga|CO3, the reduction rate of CO2 was 1.78 times higher than on Zn3Ga|CO3 LDH whereas the methanol selectivity decreased from 39 to 13mol%. Electron microscopy and UV–visible and X-ray spectroscopy detected particular interactions of the cationic layers of Zn3Ga|CO3 with Ag and Au nanoparticles. Results show that for Ag/Zn3Ga|CO3 catalysts, CO2 photoreduction by H2 under visible light was promoted by the SPR effect of Ag nanoparticles while for Au/Zn3Ga|CO3 catalysts Au nanoparticles might act as electron-trapping active sites.
The laboratory records of 405 patients with Kawasaki disease before and after intravenous immunoglobulin (IVIG) therapy were compared between the IVIG-responsive (n = 320) and IVIG-resistant (n = 85) ...groups. A high neutrophil-to-lymphocyte ratio and a high platelet-to-lymphocyte ratio before IVIG, especially when combined, were useful predictors for IVIG resistance in Kawasaki disease.
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•A new class of compound comprising tetragonal Ti8O8(OH)412+ was synthesized.•The Ti8 clusters were interlinked by terephthalates and Cu2(OH)62− linkers.•Direct links between ...Cu2(OH)62− and Ti8O8(OH)412+ were confirmed by EXAFS.•This compound functioned very well for CO PROX in predominantly H2 gas.•This compound is a catalytic crystalline model of interface Cu sites on TiO2.
The importance of metal–support interfaces is widely known in commercial and fundamental heterogeneous catalysis; however, it is difficult to characterize the active interface sites. In this study, we synthesize a new class of compound comprising tetragonal Ti8O8(OH)412+ clusters interlinked by terephthalates (bdc) and Cu2(OH)62− linkers {Ti8O8(OH)4·(bdc)2·Cu2(OH)64}. The crystalline structure was refined for X-ray diffraction and direct links between Cu2(OH)62− and Ti8O8(OH)412+ are confirmed by extended X-ray absorption fine structure. This compound functions very well (k=0.117min−1 in CO 63Pa+O2 76Pa at 323K) as a catalytic model of interface Cu sites on ultra-dispersed Ti hydrooxide for preferential oxidation of CO in predominantly H2 gas, that is important for the purification of hydrogen used in fuel cells. In comparison, mean 1.7-nm CuO nanoparticles embedded inside the pores of MIL125 were inert (k=0.0035min−1) because of the absence of links between Cu and Ti8O8(OH)412+ clusters. In CO 0.51kPa+O2 0.51kPa at 323K, the conversion to CO2 and CO PROX selectivity using Ti8O8(OH)4·(bdc)2·Cu2(OH)64 (76% and 99%) was significantly higher than that using CuO/CeO2 (28% and 96%, respectively) for 24h.
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