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Potassium-ion batteries are a compelling technology for large scale energy storage due to their low-cost and good rate performance. However, the development of potassium-ion batteries remains in its infancy, mainly hindered by the lack of suitable cathode materials. Here we show that a previously known frustrated magnet, KFeC 2 O 4 F, could serve as a stable cathode for potassium ion storage, delivering a discharge capacity of ~112 mAh g −1 at 0.2 A g −1 and 94% capacity retention after 2000 cycles. The unprecedented cycling stability is attributed to the rigid framework and the presence of three channels that allow for minimized volume fluctuation when Fe 2+ /Fe 3+ redox reaction occurs. Further, pairing this KFeC 2 O 4 F cathode with a soft carbon anode yields a potassium-ion full cell with an energy density of ~235 Wh kg −1 , impressive rate performance and negligible capacity decay within 200 cycles. This work sheds light on the development of low-cost and high-performance K-based energy storage devices. The abundance and low cost of potassium makes potassium batteries a promising technology for large scale energy storage. Here the authors apply a previously known frustrated magnet, KFeC 2 O 4 F, as the cathode in which the unique structure and Fe 2+ /Fe 3+ redox enable excellent cycling stability.

Numerous studies suggest that modification with functional nanomaterials can enhance the electrode electrocatalytic activity, sensitivity, and selectivity of the electrochemical sensors. Here, a highly sensitive and cost-effective disposable non-enzymatic glucose sensor based on copper(II)/reduced graphene oxide modified screen-printed carbon electrode is demonstrated. Facile fabrication of the developed sensing electrodes is carried out by the adsorption of copper(II) onto graphene oxide modified electrode, then following the electrochemical reduction. The proposed sensor illustrates good electrocatalytic activity toward glucose oxidation with a wide linear detection range from 0.10 mM to 12.5 mM, low detection limit of 65 µM, and high sensitivity of 172 μA mM –1  cm –2 along with satisfactory anti-interference ability, reproducibility, stability, and the acceptable recoveries for the detection of glucose in a human serum sample (95.6–106.4%). The copper(II)/reduced graphene oxide based sensor with the superior performances is a great potential for the quantitation of glucose in real samples.

Vast bulk recombination of photo-generated carriers and sluggish surface oxygen evolution reaction (OER) kinetics severely hinder the development of photoelectrochemical water splitting. Herein, through constructing a vertically ordered ZnInS nanosheet array with an interior gradient energy band as photoanode, the bulk recombination of photogenerated carriers decreases greatly. We use the atomic layer deposition technology to introduce Fe-In-S clusters into the surface of photoanode. First-principles calculations and comprehensive characterizations indicate that these clusters effectively lower the electrochemical reaction barrier on the photoanode surface and promote the surface OER reaction kinetics through precisely affecting the second and third steps (forming processes of O* and OOH*) of the four-electron reaction. As a result, the optimal photoanode exhibits the high performance with a significantly enhanced photocurrent of 5.35 mA cm −2 at 1.23 V RHE and onset potential of 0.09 V RHE . Present results demonstrate a robust platform for controllable surface modification, nanofabrication, and carrier transport. The sluggish oxygen evolution reaction kinetics severely hinder the development of photoelectrochemical water splitting. Here the authors introduce Fe-In-S clusters onto the surface of photoanode to effectively lower the electrochemical reaction barrier.

This work reports on a high-performance supercapacitor of cerium oxide/carbon nanofiber (CeO2/CNF) nanocomposites prepared by the combination of electrospinning and thermal treatment techniques. The superior capacitive performance of the CeO2/CNF nanocomposites could be attributed to the presence of Ce3+/Ce4+ and the highly porous structure determined by x-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller. The CeO2/CNF nanocomposites with various CeO2:CNF ratios (CeO2 = 10 wt%, 20 wt%, and 40 wt%) exhibited a highly porous structure with average pore size and specific surface area of 3.28 nm and 754 m2g−1, respectively. By using the XPS technique, the presence of Ce3+ and Ce4+ in all the CeO2/CNFs samples has been confirmed. The CeO2/CNF electrodes exhibit a pseudocapacitive behavior with the specific capacitance ranging from 103.47 Fg−1 to 211.84 Fg−1 at a current density of 1 Ag−1. Among our samples, the CeO2/CNF 20 wt% exhibits the highest specific capacitance of 232.86 Fg−1 (equivalent to an energy density of 37.97 Whkg−1) and a very high-power density (136.88 Wkg−1 × 103 Wkg−1) with the capacitive retention of >97% after 1000 charge/discharge cycles. This work suggests that the CeO2/CNF nanocomposites could be a promising candidate to be used as the electroactive material for supercapacitor applications.

The growing demand for advanced lithium-ion batteries calls for the continued development of high-performance positive electrode materials. Polyoxyanion compounds are receiving considerable interest as alternative cathodes to conventional oxides due to their advantages in cost, safety and environmental friendliness. However, polyanionic cathodes reported so far rely heavily upon transition-metal redox reactions for lithium transfer. Here we show a polyanionic insertion material, Li 2 Fe(C 2 O 4 ) 2 , in which in addition to iron redox activity, the oxalate group itself also shows redox behavior enabling reversible charge/discharge and high capacity without gas evolution. The current study gives oxalate a role as a family of cathode materials and suggests a direction for the identification and design of electrode materials with polyanionic frameworks. Polyoxyanion compounds are alternative cathodes to conventional oxides, but their reliance on the transition metal redox limits the performance. Here the authors report an oxalate system which possesses additional polyanionic redox reactivity, suggesting a new direction for cathode materials design.

The Mn 1-x Ni x Co 2 O 4 (0.00 ≤  x  ≤ 0.20) nanoparticles were synthesized by a simple PAN-solution route. XRD, TEM, SAED, FESEM, XANES, XPS, and BET techniques were used to investigate the structural and morphology of Ni-doped MnCo 2 O 4 nanoparticles. The effect of Ni ions substitution in MnCo 2 O 4 nanoparticles on the electrochemical properties was examined on three-electrode systems. The results show that the substitution of Mn with Ni ions can improve the electrochemical properties of MnCo 2 O 4 nanoparticles. The Mn 1-x Ni x Co 2 O 4 electrode with x  = 0.15 exhibits the highest specific capacitance of 378 F g −1 at the current density of 1 A g −1 . After 1000 charge-discharges times, this electrode has good capacity retention of 85%. The good capacitance characteristics and cyclic stability indicate that these Mn 1-0.85 Ni 0.15 Co 2 O 4 nanoparticles could be applied as active materials for energy storage devices.

The occurrence of manganese in groundwater causes coloured water and pipe rusting in water treatment systems. Consumption of manganese-contaminated water promotes neurotoxicity in humans and animals. Manganese-oxidizing bacteria were isolated from contaminated areas in Thailand for removing manganese from water. The selected bacterium was investigated for its removal kinetics and mechanism using synchrotron-based techniques. Among 21 isolates, Streptomyces violarus strain SBP1 (SBP1) was the best manganese-oxidizing bacterium. At a manganese concentration of 1 mg L −1 , SBP1 achieved up to 46% removal. The isolate also successfully removed other metal and metalloid, such as iron (81%) and arsenic (38%). The manganese concentration played a role in manganese removal and bacterial growth. The observed self-substrate inhibition best fit with the Aiba model. Kinetic parameters estimated from the model, including a specific growth rate, half-velocity constant, and inhibitory constant, were 0.095 h −1 , 0.453 mg L −1 , and 37.975 mg L −1 , respectively. The synchrotron-based techniques indicated that SBP1 removed manganese via combination of bio-oxidation (80%) and adsorption (20%). The study is the first report on biological manganese removal mechanism using synchrotron-based techniques. SBP1 effectively removed manganese under board range of manganese concentrations. This result showed the potential use of the isolate for treating manganese-contaminated water.

CaCu 3 Ti 4 O 12 (CCTO) ceramic powders were successfully prepared by a wet-chemical combustion method. The phase formation, microstructure, giant dielectric response, and nonlinear electrical properties of the sintered ceramics were systematically investigated. The main phase in the CCTO powder is clearly indicated in the XRD pattern. A dense and fine-grained microstructure was obtained by sintering the compacted CCTO powders. Dielectric permittivity values are in the range of ~ 10 3 –10 4 with a very low tan δ of ~ 0.03–0.11 at 1 kHz. Interestingly, a high breakdown electric field (9741.6 V/cm) and nonlinear coefficient (9.9) are observed in the CCTO ceramic sintered at 1030 °C for 1 h. Impedance spectroscopy analysis revealed that the electrical conductivity in the grains and grain boundaries is completely different. The electrically heterogeneous microstructure clearly indicates that the giant dielectric response and nonlinear electrical properties are correlated with the electrical response of the insulating grain boundaries. The origin of the n -type semiconducting grains is evident by considering the oxidation states of the Ti and Cu ions, which are quantitatively and qualitatively analyzed using X-ray absorption spectroscopy.

Although manganese oxide- and graphene-based supercapacitors have been widely studied, their charge storage mechanisms are not yet fully investigated. In this work, we have studied the charge storage mechanisms of K-birnassite MnO 2 nanosheets and N-doped reduced graphene oxide aerogel (N-rGO ae ) using an in situ X-ray absorption spectroscopy (XAS) and an electrochemical quart crystal microbalance (EQCM). The oxidation number of Mn at the MnO 2 electrode is +3.01 at 0 V vs. SCE for the charging process and gets oxidized to +3.12 at +0.8 V vs. SCE and then reduced back to +3.01 at 0 V vs. SCE for the discharging process. The mass change of solvated ions, inserted to the layers of MnO 2 during the charging process is 7.4 μg cm −2 . Whilst, the mass change of the solvated ions at the N-rGO ae electrode is 8.4 μg cm −2 . An asymmetric supercapacitor of MnO 2 //N-rGO ae (CR2016) provides a maximum specific capacitance of ca. 467 F g −1 at 1 A g −1 , a maximum specific power of 39 kW kg −1 and a specific energy of 40 Wh kg −1 with a wide working potential of 1.6 V and 93.2% capacity retention after 7,500 cycles. The MnO 2 //N-rGO ae supercapacitor may be practically used in high power and energy applications.

The substitution of ZnO for CaO site and the limitation of ZnO addition in the sol-gel ionomer glass composition at different calcination temperatures were evaluated and characterized in-depth by X-ray powder diffraction and X-ray photoelectron spectroscopy techniques in this study. The relationship between the compressive strength and the final cement structure was demonstrated by the ion-releasing behavior and synchrotron-based X-ray absorption spectroscopy (XAS) technique. The setting time, in vitro cytotoxicity, bioactivity and tooth adhesion ability of the sol-gel GICs were also evaluated. As expected, ZnO containing GICs presented antibacterial properties under the visible light condition as photocatalysis effect. Although the low crosslinking ability of Zn atoms to the polyacrylic liquid reduced the compressive strength, the compressive strength could be improved by compromising the calcination temperature. Moreover, this study also shows that the ZnO containing GICs had promising results on the biological properties which offered potential advantages in clinical use.