The pH monitoring is significantly important in chemical industry, biological process, and pollution treatment. However, it remains a great challenge to measure pH in extreme alkalinity conditions. Herein, we employ an electrolyte-gated field-effect-transistor (FET) strategy using non-stoichiometric SrCoO_x with rich oxygen-vacancy defects as channel materials for detecting extreme alkalinity. The corresponding channel can provide effective oxygen-ion-migration sites for reversible transformation of OH⁻ ↔ O²⁻ + H⁺ driven by electric field. The resultant electrolyte-gated FET sensor exhibits a sensitive linear response to high concentrations of alkaline solution, 1–20 M. Significantly, the sensor has the ability to directly indicate the pH values ranging from 14.0 to 17.0 in consideration of ion-activity coefficient data. This work offers a great possibility for directly detecting base concentration as well as pH values in extreme alkaline solutions.

Large scale applications of metal-iodine batteries working at sub-zero degree have been challenged by the limited capacity and performance degradation. Herein, we firstly propose a Zn-I₂ battery working at low temperature with a carbon composite material/iodine (CCM-I₂) cathode, a Zn anode and an environmentally tolerable Zn(ClO₄)₂-ACN electrolyte. The CCM framework with hierarchical porous structure endows a powerful iodine-anchoring to overcome undesirable dissolution of iodine in organic electrolyte, and the Zn(ClO₄)₂-ACN electrolyte with low freezing point and high ionic conductivity enhances the low temperature performance. The synergies enable an efficiently reversible conversion of Zn-I₂ battery even at −40 °C. Therefore, the resultant Zn-I₂ battery delivers a high specific capacity of 200 mAh·g⁻¹, which is fairly approximate to the theoretical capacity of I₂ (211 mAh·g⁻¹) and a superior cycling stability with minimal capacity fading of 0.00043% per cycle over 7,000 times under 2C at −20 °C. Furthermore, even at −40 °C, this Zn-I₂ battery still exhibits a good capacity retention of 68.7% compared to the capacity at 25 °C and a rapid capacity-recover ability with elevating temperature change. Our results distinctly indicate this Zn-I₂ battery can be competent for the practical application under low temperature operation.

Crystal phase engineering on CuInS₂ (CIS) nanocrystals, especially polytypic structure, has become one of the research hotspots to design the advanced materials and devices for energy conversion and environment treatment. Here, the polytypic CIS nanosheets (NSs) including zincblende/wurtzite and chalcopyrite/wurtzite types were first time achieved in a hot-injection system using oleic acid and liquid paraffin as the reaction media. As-obtained polytypic CIS NSs exhibit significantly enhanced light-absorption ability and visible-light-driven photocatalytic performance originating from the rational hetero-crystalline interfaces and surface defect states, which efficiently inhibit the recombination of photo-generated carriers. Meanwhile, the polytypic CIS NSs were spin-coated onto the surface of fluorinated-tin oxide glass substrate and used as the photoelectrode, which shows an excellent photoelectrochemical (PEC) activity in aqueous solution. The present work not only provides a facile, rapid, low-cost, and environmental-friendly synthesis strategy to design the crystal phase and defect structure of ternary chalcogenides, but also demonstrates the relationships between the polytypic structure and photocatalytic/photoelectrochemical properties.

In the development of wearable energy devices, polypyrrole (PPy) is considered as a promising electrode material owing to its high capacitance and good mechanical flexibility. Herein, we report a PPy-based hybrid structure consisting of vertical PPy nanotube arrays and carbon nano-onions (CNOs) grown on textile for wearable supercapacitors. In this hybrid nanostructure, the vertical PPy nanotubes provide straight and superhighways for electron and ion transport, boosting the energy storage; while the CNOs mainly act as a conductivity retainer for the underlayered PPy film during stretching. A facile template-degrading method is developed for the large-area growth of the PPy-based hybrid nanostructures on the textile through one-step polymerization process. The fabricated stretchable supercapacitor exhibits superior energy storage capacitance with the specific capacitance of 64 F·g⁻¹. Also, it presents the high capacitance retention of 99% at a strain of 50% after 500 stretching cycles. Furthermore, we demonstrate that the textile-based stretchable supercapacitor device can provide a stable energy storage performance in different wearable situations for practical applications. The use of the PPy-based hybrid nanostructures as the supercapacitor electrode offers a novel structure design and a promising opportunity for wearable power supply in real applications.

Transition metal phosphides (TMPs) are promising candidates for noble metal free electrocatalysts in water splitting applications. In this work, we present the facile synthesis of nickel cobalt phosphide electrocatalyst with three-dimensional nanostructure (3D-NiCoP) on the nickel foam, via hydrothermal reaction and phosphorization. The as-prepared electrocatalyst exhibits an excellent activity for hydrogen evolution reaction (HER) in both acidic and alkaline electrolytes, with small overpotentials to drive 10 mA/cm² (80 mV for 0.5 M H₂SO₄, 105 mV for 1 M KOH), small Tafel slopes (37 mV/dec for 0.5 M H₂SO₄, 79 mV/dec for 1 M KOH), and satisfying durability in long-term electrolysis. 3D-NiCoP also shows a superior HER activity compared to single metal phosphide, such as cobalt phosphide and nickel phosphide. The outstanding performance for HER suggests the great potential of 3D-NiCoP as a highly efficient electrocatalyst for water splitting technology.

Rechargeable metal-iodine batteries are an emerging attractive electrochemical energy storage technology that combines metallic anodes with halogen cathodes. Such batteries using aqueous electrolytes represent a viable solution for the safety and cost issues associated with organic electrolytes. A hybrid-electrolyte battery architecture has been adopted in a lithium-iodine battery using a solid ceramic membrane that protects the metallic anode from contacting the aqueous electrolyte. Here we demonstrate an eco-friendly, low-cost zinc-iodine battery with an aqueous electrolyte, wherein active I2 is confined in a nanoporous carbon cloth substrate. The electrochemical reaction is confined in the nanopores as a single conversion reaction, thus avoiding the production of I₃^- intermediates. The cathode architecture fully utilizes the active I₂, showing a capacity of 255 mAh·g^-1 and low capacity cycling fading. The battery provides an energy density of ~ 151 Wh·kg^-1 and exhibits an ultrastable cycle life of more than 1, 500 cycles.

Herein, carbon nano-onions (CNOs) with different structures have been investigated as precursors for the synthesis of graphene quantum dots (GQDs). It was found that hollow CNOs yield GQDs with a uniform size distribution, whereas metal encapsulation in the CNO structure is disadvantageous for the same. Furthermore, the hollow CNOs are also advantageous for the synthesis of GQDs with a yellow-green hybrid luminescence and long-ranged excitation wavelength (λ_ex)-independent photoluminescent (PL) behavior, in which the λ_ex upper limit was 480 nm. These features enable safe sensing and cell tracking applications with a longer excitation wavelength in the visible light region. The potential applications of the synthesized GQDs as fluorescent sensing probes for detecting Cu(Ⅱ) ions and non-toxic cell imaging under visible light excitation have been demonstrated. This means that sensing and bioimaging can be accomplished in the natural environment with no need for UV excitation. This work provides a reference to researchers in tailoring CNO structures in terms of their inner space to synthesize GQDs with the desired luminescence behavior.