Tunable Impedance of Cobalt Loaded Carbon for Wide-Range Electromagnetic Wave Absorption.

Impedance matching modulation of the electromagnetic wave (EMW) absorbers toward broad effective absorption bandwidth (EAB) is the ultimate aim in EMW attenuation applications. Here, a Joule heating strategy is reported for preparation of the Co-loaded carbon (Co/C) absorber with tunable impedance characteristics. Typically, the size of the Co can be regulated to range from single-atoms to clusters, and to nanocrystals. The varied sizes of the Co combined with different graphitization degrees of carbon can result in different relative input impedances and electromagnetic loss, leading to the tunable EMW absorption properties of the Co/C absorber. By meticulously coalescing the different prepared Co/C, the working frequency can be easily tuned, covering Ku, X, and C bands. Furthermore, the Co/C demonstrates a high EMW attenuation due to its unique dielectric loss capability and magnetic loss characteristics. The abundant interfaces of Co/C can also contribute to the enhanced interfacial polarization for improving EMW attenuation. This work demonstrates the importance of optimizing the metal and carbon interaction to the impedance matching toward wide EAB of the EMW absorbers.

Light-driven flow synthesis of acetic acid from methane with chemical looping.

Oxidative carbonylation of methane is an appealing approach to the synthesis of acetic acid but is limited by the demand for additional reagents. Here, we report a direct synthesis of CH3COOH solely from CH4 via photochemical conversion without additional reagents. This is made possible through the construction of the PdO/Pd-WO3 heterointerface nanocomposite containing active sites for CH4 activation and C-C coupling. In situ characterizations reveal that CH4 is dissociated into methyl groups on Pd sites while oxygen from PdO is the responsible for carbonyl formation. The cascade reaction between the methyl and carbonyl groups generates an acetyl precursor which is subsequently converted to CH3COOH. Remarkably, a production rate of 1.5 mmol gPd-1 h-1 and selectivity of 91.6% toward CH3COOH is achieved in a photochemical flow reactor. This work provides insights into intermediate control via material design, and opens an avenue to conversion of CH4 to oxygenates.

Limiting the Uncoordinated N Species in M-Nx Single-Atom Catalysts toward Electrocatalytic CO2 Reduction in Broad Voltage Range.

Carbon-supported single-atom catalysts (SACs) are extensively studied because of their outstanding activity and selectivity toward a wide range of catalytic reactions. Amidst its development, excess dopants (e.g., nitrogen) are always required to ensure the high loading content of SACs on the carbon support. However, the use of excess dopants is accompanied by formation of miscellaneous structures (particularly the uncoordinated N species) on catalysts, leading to adverse effects on their performance. Herein, the synthesis of carbon-supported Ni SACs with precisely controlled single-atom structure via joule heating strategy, showing the coordination of 80% of N dopants with metal elements, is reported. The preclusion of the unfavorable N species is confirmed to be the main reason for the superior performance of optimized Ni SACs in electrocatalytic carbon dioxide reduction reaction, which demonstrates unprecedented activity, selectivity, and stability under an exceptionally broad voltage range (>92% CO selectivity in the range of -0.7 to -1.9 V reversible hydrogen electrode). Such a synthetic strategy is further applicable for the design of SACs with various metals. This work demonstrates a facile method for preclusion of unfavorable dopants in the SACs and its importance in catalytic application.

Efficient Photoelectrochemical Conversion of Methane into Ethylene Glycol by WO3 Nanobar Arrays.

Photoelectrochemical (PEC) conversion of methane (CH4 ) has been extensively explored for the production of value-added chemicals, yet remains a great challenge in high selectivity toward C2+ products. Herein, we report the optimization of the reactivity of hydroxyl radicals (. OH) on WO3 via facet tuning to achieve efficient ethylene glycol production from PEC CH4 conversion. A combination of materials simulation and radicals trapping test provides insight into the reactivity of . OH on different facets of WO3 , showing the highest reactivity of surface-bound . OH on {010} facets. As such, the WO3 with the highest {010} facet ratio exhibits a superior PEC CH4 conversion efficiency, reaching an ethylene glycol production rate of 0.47 µmol cm-2 h-1 . Based on in situ characterization, the methanol, which could be attacked by reactive . OH to form hydroxymethyl radicals, is confirmed to be the main intermediate for the production of ethylene glycol. Our finding is expected to provide new insight for the design of active and selective catalysts toward PEC CH4 conversion.

Integrated contact lens sensor system based on multifunctional ultrathin MoS2 transistors.

Smart contact lenses attract extensive interests due to their capability of directly monitoring physiological and ambient information. However, previous demonstrations usually lacked efficient sensor modalities, facile fabrication process, mechanical stability, or biocompatibility. Here, we demonstrate a flexible approach for fabrication of multifunctional smart contact lenses with an ultrathin MoS2 transistors-based serpentine mesh sensor system. The integrated sensor systems contain a photodetector for receiving optical information, a glucose sensor for monitoring glucose level directly from tear fluid, and a temperature sensor for diagnosing potential corneal disease. Unlike traditional sensors and circuit chips sandwiched in the lens substrate, this serpentine mesh sensor system can be directly mounted onto the lenses and maintain direct contact with tears, delivering high detection sensitivity, while being mechanically robust and not interfering with either blinking or vision. Furthermore, the in vitro cytotoxicity tests reveal good biocompatibility, thus holding promise as next-generation soft electronics for healthcare and medical applications.

Scalable Fabrication of Highly Active and Durable Membrane Electrodes toward Water Oxidation.

The electrocatalytic oxygen evolution reaction (OER) is a highly important reaction that requires a relatively high overpotential and determines the rate of water splitting-a process for producing hydrogen. The overall OER performance is often largely limited by uncontrollable interface when active catalysts are loaded on conductive supports, for which polymer binders are widely used, but inevitably block species transportation channels. Here, a scalable fabrication approach to freestanding graphitized carbon nanofiber networks is reported, which provides abundant sites for in situ growing Fe/Ni catalysts with the improved interface. The fabricated hybrid membrane exhibits high activity and durability toward OER, with an overpotential of 280 mV at a geometrical current density of 10 mA cm-2 and a Tafel slope of 30 mV dec-1 in alkaline medium. As implemented as a freestanding electrode, the 3D hybrid structure achieves further enhanced OER performance with an overpotential down to 215 mV at 10 mA cm-2 . This work provides fresh insights into rationally fabricating OER electrocatalysts from the angle of electrode design.

Application of vacuum assisted venous drainage in heart surgeries for newborns.

OBJECTIVE: To explore the role of cardiopulmonary bypass (CPB) with vacuum assisted venous drainage(VAVD)in the management of newborns with congenital heart diseases. METHODS: Total 15 newborns with congenital heart diseases (11 males and 4 females)underwent heart operations. Their age ranged from 2 days to 28 days [mean:(15.67 ± 2.22)days], and their body weight from 2.3 kg to 4.8 kg [mean: (3.75 ± 0.19)kg]. Sternal median incision was made to establish CPB,during which VAVD was applied for all the newborns. RESULTS: In these 15 newborns,the mean CPB time was from 50 minutes to 343 minutes [mean:(170.3 ± 26.6)minutes], and the mean aortic clamping time ranged from 20 minutes to 172 minutes [mean:(85.8 ± 14.6)minutes]. No macroscopic hematuria, inadequate drainage, or cannulation vena cava difficulty was observed during the procedures. All the newborns were successfully weaned from the machine. No neurological complication due to micro air embolus caused by negative pressure was noted. No vena cava infarction, thrombosis, or other complication was reported after the surgery, although one patient died after the surgery and another patient was discharged upon its family's own decision. CONCLUSIONS: VAVD is a safe, simple, and cost-effective technique. Appropriate negative pressure can the resistance during thinner venous intubation and thus speed up blood drainage,provide adequate perfusion flow,and reduce the pre-filling volume.