Developing acid‐stable electrocatalysts with high activity for the oxygen evolution reaction (OER) is of paramount importance for many energy‐related technologies. This work reports that ultrathin ...nitrogen‐doped carbon coated oxygen‐vacancy (Vo·) rich RuO2 nanoparticles on carbon nanotubes (CNTs) (NC@Vo·‐RuO2/CNTs‐350), synthesized through the controlled calcination in air, is an efficient acid‐stable electrocatalyst for the OER. It only needs an overpotential of 170.0 mV to drive 10.0 mA cm−2 and shows excellent stability with no distinguishable activity loss observed for >900 h. Its mass activity is >110 times higher than the commercial RuO2. In particular, an electrolyzer assembled with this catalyst shows a record‐low cell voltage of 1.45 V to deliver 10.0 mA cm−2 and exhibits a low performance drop for >1000 h. The NC@Vo·‐RuO2/CNTs‐350 also shows super‐high catalytic activities and excellent stabilities for OER in neutral and alkaline media. DFT calculations indicate that its high catalytic activity mainly arises from the strong electronic coupling between RuO2 and NC/CNTs, which increases the oxidation state and catalytic activity of Ru at the active site and improves the stabilities of lattice oxygen and surface Ru during the OER processes. The presence of Vo· can strengthen the electronic coupling between RuO2 and NC/CNTs.
Ultrathin carbon coating and defect engineering are employed to improve the catalytic activity and stability of RuO2 for the acidic oxygen evolution reaction (OER). The obtained NC@Vo·‐RuO2/CNTs‐350 show super‐high activity for OER, with only an overpotential of 170.0 mV to drive 10.0 mA cm−2, and excellent stability with no distinguishable activity loss observed for >900 h.
A plasma approach is reported to synthesize carbon cloth supported carbon fiber and oxygen defect‐rich NiCoO/NiCoN hetero‐nanowire co‐integrated hybrid catalyst (P‐NCO/NCN‐CF@CC), which includes the ...advanced features of carbon integration, cation doping, defect/vacancy introduction, and heterostructuring. The P‐NCO/NCN shows a fascinating structure with the periphery composed of NCO and the interior co‐composed of NCO and NCN. Its formation mainly depends on the high reactivity of energetic species of NH, Ha, and Hb formed during the plasma discharge. The P‐NCO/NCN‐CF@CC exhibits the oxygen reduction reaction (ORR) activity comparable to the Pt/C and the oxygen evolution reaction (OER) activity higher than RuO2. When used in the all‐solid‐state zinc‐air batteries, it gives a high maximum power density of 109.8 mW cm−2 with no performance drop observed for >300 cycles. The DFT calculations indicate that the NCO/NCN heterostructuring and oxygen defects in NCO play the important roles in the high ORR/OER activities of the catalyst. They can modulate the electronic structure of the catalyst, lowering the energy barriers of rate determining steps.
The plasma approach is employed to the synthesis of the oxygen defective NiCoO/NiCoN heterostructure with improved ORR/OER activities, which includes the advanced features of carbon integration, cation doping, defect/vacancy introduction, and heterostructuring. The assembled flexible all‐solid‐state zinc‐air batteries exhibit an open circuit voltage of 1.48 V and deliver a maximum power density of 109.8 mW cm−2.
The development of cost‐effective catalysts for oxygen evolution reaction (OER) in acidic media is of paramount importance. This work reports that Sr‐doped solid solution structural ultrafine IrMnO2 ...nanoparticles (NPs) (≈1.56 nm) on the carbon nanotubes (Sr‐IrMnO2/CNTs) are efficient catalysts for the acidic OER. Even with the Ir use dosage 3.5 times lower than that of the commercial IrO2, the Sr‐IrMnO2/CNTs only need an overpotential of 236.0 mV to drive 10.0 mA cm−2 and show outstanding stability for >400.0 h. Its Ir mass activity is 39.6 times higher than that of the IrO2 at 1.53 V. The solid solution and Sr‐doping structure of Sr‐IrMnO2 are the main origin of the high catalytic activity and excellent stability of the Sr‐IrMnO2/CNTs. The density function theory calculations indicate that the solid solution structure can promote strong electronic coupling between Ir and Mn, lowering the energy barrier of the OER rate‐determining step. The Sr‐doping can enhance the stability of Ir against the chemical corrosion and demetallation. Water electrolyzers and proton exchange membrane water electrolyzers assembled with the Sr‐IrMnO2/CNTs show superb performance and excellent durability in the acid media.
Sr‐doped solid solution structural ultrafine IrMnO2 nanoparticles (NPs) on the CNTs (Sr‐IrMnO2/CNTs) are efficient and durable catalysts for the acidic OER. The solid solution structure promotes the s electronic coupling between Ir and Mn, improving their OER activity, while the Sr doping enhances the stability of Sr‐IrMnO2, improving the durability of the Sr‐IrMnO2/CNTs.
Nationwide nonpharmaceutical interventions (NPIs) have been effective at mitigating the spread of the novel coronavirus disease (COVID-19), but their broad impact on other diseases remains ...under-investigated. Here we report an ecological analysis comparing the incidence of 31 major notifiable infectious diseases in China in 2020 to the average level during 2014-2019, controlling for temporal phases defined by NPI intensity levels. Respiratory diseases and gastrointestinal or enteroviral diseases declined more than sexually transmitted or bloodborne diseases and vector-borne or zoonotic diseases. Early pandemic phases with more stringent NPIs were associated with greater reductions in disease incidence. Non-respiratory diseases, such as hand, foot and mouth disease, rebounded substantially towards the end of the year 2020 as the NPIs were relaxed. Statistical modeling analyses confirm that strong NPIs were associated with a broad mitigation effect on communicable diseases, but resurgence of non-respiratory diseases should be expected when the NPIs, especially restrictions of human movement and gathering, become less stringent.
Natural biomolecules have potential as proton‐conducting materials, in which the hydrogen‐bond networks can facilitate proton transportation. Herein, a biomolecule/metal–organic framework (MOF) ...approach to develop hybrid proton‐conductive membranes is reported. Single‐strand DNA molecules are introduced into DNA@ZIF‐8 membranes through a solid‐confined conversion process. The DNA‐threaded ZIF‐8 membrane exhibits high proton conductivity of 3.40 × 10−4 S cm−1 at 25 °C and the highest one ever reported of 0.17 S cm−1 at 75 °C, under 97% relatively humidity, attributed to the formed hydrogen‐bond networks between the DNA molecules and the water molecules inside the cavities of the ZIF‐8, but very low methanol permeability of 1.25 × 10−8 cm2 s−1 due to the small pore entrance of the DNA@ZIF‐8 membranes. The selectivity of the DNA@ZIF‐8 membrane is thus significantly higher than that of developed proton‐exchange membranes for fuel cells. After assembling the DNA@ZIF‐8 hybrid membrane into direct methanol fuel cells, it exhibits a power density of 9.87 mW cm−2 . This is the first MOF‐based proton‐conductivity membrane used for direct methanol fuel cells, providing bright promise for such hybrid membranes in this application.
A DNA‐threaded DNA@ZIF‐8 membrane demonstrates ultrahigh proton conductivity and low methanol permeability, holding great potential for application in direct methanol fuel cells.
Aim
Up‐to‐date epidemiological studies on the global burden of severe periodontitis is scarce. This study aimed to present the latest estimates for prevalence of severe periodontitis from 1990 to ...2019, by region, age, and level of socio‐demographic development.
Materials and Methods
Estimates from the Global Burden of Disease study 2019 were used to investigate burden and trends of prevalence of severe periodontitis and its association with socio‐demographic development at global, regional, and national level. Decomposition analysis was performed to explore the contribution of demographic and epidemiological factors to the evolving burden of severe periodontitis.
Results
In 2019, there were 1.1 billion (95% uncertainty interval: 0.8–1.4 billion) prevalent cases of severe periodontitis globally. From 1990 to 2019, age‐standardized prevalence rate of severe periodontitis increased by 8.44% (6.62%–10.59%) worldwide. Prevalence of severe periodontitis is higher among less developed countries/regions. Global population growth accounted for 67.9% of the increase in the number of prevalent cases of severe periodontitis from 1990 to 2019.
Conclusions
The global burden of severe periodontitis has been substantial and increasing over the past three decades. Upstream policy changes are urgently needed to address the global public health challenge of severe periodontitis.
This work reports an amorphization and partial desulfurization method to improve the performance of sulfide‐based materials for Na+ storage. Specifically, the polypyrrole derived carbon coated ...amorphous substoichiometric tin sulfide supported on aminated carbon nanotubes (PPY‐C@SnSx/ACNTs) with amorphized and substoichiometric tin sulfide (SnSx) is synthesized by simply thermal annealing the PPY‐C@SnS2/ACNTs. The PPY‐C@SnSx/ACNTs shows stable reversible capacities of 410.2 mAh g−1 for Na+ storage at 0.1 A g−1 and excellent rate capacities of 270.2, 235.5, 217.4, and 210.0 mAh g−1 at 5.0, 10.0, 20.0, and 30.0 A g−1, respectively. Nearly zero drops on the reversible capacities can be observed when it is sodiated/desodiated at 2.0, 5.0, and 10.0 A g−1 for up to 1000, 6500, 8000 cycles, respectively. Its outstanding rate capacities and degradation‐free cycling stabilities mainly arise from the amorphized and substoichiometric structure of SnSx, which improve the reversible capacities and Na+ diffusivities of the PPY‐C@SnSx/ACNTs. The density functional theory (DFT) calculations indicate that the partial desulfurization can improve the electric conductivity and promote the sodiation/desodiation of SnSx. It explains why the PPY‐C@SnSx/ACNTs can exhibit high performance for Na+ storage well.
The amorphization and partial desulfurization is demonstrated to be a promising method to improve the performance of sulfide‐based materials for Na+ storage. It indicates that the amorphization and partial desulfurization can improve the electric conductivity, Na+ diffusivity, and sodiation/desodiation of the sulfide‐based materials, giving them super high‐rate capacity and degradation‐free cycling stability.
This technical note presents analytical investigations of reachability and controllability of Boolean control networks (BCNs) with pinning controllers. Based on semi-tensor product (STP) of matrices, ...BCNs with pinning controllers are converted into a discrete-time algebraic system. A formula is derived to calculate the number of different control sequences steering BCNs between two states in a given step, and then several necessary and sufficient criteria are derived for reachability and controllability of BCNs with pinning controllers. Moreover, we make a comparison among three forms of BCNs, which have similar algebraic representations. Finally, we obtain some efficient conditions to judge the dynamic structure of BCNs.
Plasma treatment and reduction are used to synthesize Pt nanoparticles (NPs) on nitrogen-doped carbon nanotubes (p-Pt/p-NCNT) with a low Pt content. In particular, the plasma treatment is used to ...treat the NCNT to give it with more surface defects, facilitating a better growth of the Pt NPs, while the plasma reduction produces the Pt NPs with a reduced fraction of the surface atoms at the high oxidation states, increasing the catalytic activities of the p-Pt@p-NCNT. Even at the low Pt content (7.8 wt.%), the p-Pt@p-NCNT shows superior catalytic activities and good stabilities for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). The density functional theory (DFT) calculations indicate that the defects generated in the plasma treatment can help the growth of the Pt NPs on the NCNTs, leading to the stronger electronic coupling between Pt and NCNT and the increased stability of the catalyst. The plasma reduction can give the Pt NPs with optimized surface oxidation states, decreasing the energy barriers of the rate-determining steps for MOR and ORR. When used as the anode and cathode catalysts for the direct methanol fuel cells (DMFCs), the p-Pt@p-NCNT exhibits a higher maximum power density of 81.9 mW cm
at 80 °C and shows good durability.
This work reports a novel approach for the synthesis of FeCo alloy nanoparticles (NPs) embedded in the N,P‐codoped carbon coated nitrogen‐doped carbon nanotubes (NPC/FeCo@NCNTs). Specifically, the ...synthesis of NCNT is achieved by the calcination of graphene oxide‐coated polystyrene spheres with Fe3+, Co2+ and melamine adsorbed, during which graphene oxide is transformed into carbon nanotubes and simultaneously nitrogen is doped into the graphitic structure. The NPC/FeCo@NCNT is demonstrated to be an efficient and durable bifunctional catalyst for oxygen evolution (OER) and oxygen reduction reaction (ORR). It only needs an overpotential of 339.5 mV to deliver 10 mA cm−2 for OER and an onset potential of 0.92 V to drive ORR. Its bifunctional catalytic activities outperform those of the composite catalyst Pt/C + RuO2 and most bifunctional catalysts reported. The experimental results and density functional theory calculations have demonstrated that the interplay between FeCo NPs and NCNT and the presence of N,P‐codoped carbon structure play important roles in increasing the catalytic activities of the NPC/FeCo@NCNT. More impressively, the NPC/FeCo@NCNT can be used as the air‐electrode catalyst, improving the performance of rechargeable liquid and flexible all‐solid‐state zinc–air batteries.
The FeCo alloy nanoparticles embedded in the N,P‐codoped carbon coated nitrogen‐doped carbon nanotubes (NPC/FeCo@NCNT) have been synthesized and demonstrated to be efficient and durable catalysts for oxygen evolution and reduction reactions. It is usable as the air‐electrode catalysts to improve the performance of rechargeable liquid and flexible all‐solid‐state zinc–air batteries.
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