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Highlights: Efficient activation of Ni electrode employs chronopotentiostatic superoxidation. Novel superoxide activation mechanism realizes the redox reaction with three-electron transfer (Ni ↔ Ni3+). As-prepared CPS-Ni||Zn batteries exhibit simultaneously ultrahigh energy and power densities. Aqueous Ni–Zn microbatteries are safe, reliable and inexpensive but notoriously suffer from inadequate energy and power densities. Herein, we present a novel mechanism of superoxide-activated Ni substrate that realizes the redox reaction featuring three-electron transfers (Ni ↔ Ni3+). The superoxide activates the direct redox reaction between Ni substrate and KNiO2 by lowering the reaction Gibbs free energy, supported by in-situ Raman and density functional theory simulations. The prepared chronopotentiostatic superoxidation-activated Ni (CPS-Ni) electrodes exhibit an ultrahigh capacity of 3.21 mAh cm−2 at the current density of 5 mA cm−2, nearly 8 times that of traditional one-electron processes electrodes. Even under the ultrahigh 200 mA cm−2 current density, the CPS-Ni electrodes show 86.4% capacity retention with a Columbic efficiency of 99.2% after 10,000 cycles. The CPS-Ni||Zn microbattery achieves an exceptional energy density of 6.88 mWh cm−2 and power density of 339.56 mW cm−2. Device demonstration shows that the power source can continuously operate for more than 7 days in powering the sensing and computation intensive practical application of photoplethysmographic waveform monitoring. This work paves the way to the development of multi-electron transfer mechanisms for advanced aqueous Ni–Zn batteries with high capacity and long lifetime. [ABSTRACT FROM AUTHOR]

Facile preparation of additive-free inks with both high viscosity and high conductivity is critical for scalable screen printing of wireless electronics, yet very challenging. MXene materials exhibit excellent conductivity and hydrophilicity, showing great potential in the field of additive-free inks for screen printing. Here, we demonstrate the synthesis of additive-free two-dimensional (2D) titanium carbide MXene inks, and realize screen-printed MXene wireless electronics for the first time. The viscosity of MXene ink is solely regulated by tuning the size of MXene nanosheet without any additives, hence rendering the printed MXene film extremely high conductivity of 1.67 × 105 S/m and fine printing resolution down to 0.05 mm on various flexible substrates. Moreover, radio frequency identification (RFID) tags fabricated using the additive-free MXene ink via screen printing exhibit stable antenna reading performance and superb flexibility. This article, thus offers a new route for the efficient, low-cost and pollution-free manufacture of printable electronics based on additive-free MXene inks. [ABSTRACT FROM AUTHOR]

The zinc-rich epoxy cathodic protection coating is the most widely used anticorrosion material for marine steel. However, traditional conductive fillers lack the intelligent self-healing effect, which limits the long-term anticorrosion performance. Herein, with uniform carbon-coated ZnS (ZnS@C) nanoballs as the smart active release filler, we propose an anticorrosive and self-healing zinc-rich maleic anhydride epoxy coating. Due to the high pore filling efficiency of the nanoballs, the water vapor transmission rate of the coating with an initial corrosion efficiency of 99.92% and a low-frequency impedance of ∣Z∣f=10mHz = 3.88 × 1010 Ω·cm2, was reduced by 52%. The carbon-shell of the nanoball increases electron transmission paths in the coating and improves conductivity by nearly two orders of magnitude, which effectively activates more Zn-sites and extends the cathodic protection time. Moreover, once the steel-substrate undergoes regional corrosion, the SO42− hydrolyzes from the ZnS-core of the nanoball and reacts with iron ions on the corroded area accurately and intelligently to fill the gap and self-heals into a new dense barrier layer (Fe2(SO4)3, etc.), which significantly improves the shielding protection ability during the long-term usage of the coating. The effective anticorrosion time of the proposed coating could be up to 3,400 h. [ABSTRACT FROM AUTHOR]

The demand for green and efficient energy storage devices in daily life is constantly rising, which is caused by the global environment and energy problems. Lithium-ion batteries (LIBs), an important kind of energy storage devices, are attracting much attention. Graphite is used as LIBs anode, however, its theoretical capacity is low, so it is necessary to develop LIBs anode with higher capacity. Application strategies and research progresses of novel iron oxides and their composites as LIBs anode in recent years are summarized in this review. Herein we enumerate several typical synthesis methods to obtain a variety of iron oxides based nanostructures, such as gas phase deposition, co-precipitation, electrochemical method, etc. For characterization of the iron oxides based nanostructures, especially the in-situ X-ray diffraction and 57Fe Mössbauer spectroscopy are elaborated. Furthermore, the electrochemical applications of iron oxides based nanostructures and their composites are discussed and summarized. Graphic Abstract [ABSTRACT FROM AUTHOR]