Flexible All-Solid-State Direct Methanol Fuel Cells with High Specific Power Density.

It is vital to create flexible batteries as power sources to suit the needs of flexible electronic devices because they are widely employed in wearable and portable electronics. The direct methanol fuel cell (DMFC) is a desirable alternative portable energy source since it is a clean, safe, and high energy density cell. The traditional DMFC in mechanical assembly and its unbending property, however, prevent it from being employed in flexible electrical devices. In this study, the flexible membrane electrode assembly (MEA) with superior electrical conductivity and nanoscale TiC-modified carbon cloth (TiC/CC) is used as supporting layer. Additionally, solid methanol fuels used in the manufacturing of flexible all-solid-state DMFC have the advantages of being tiny, light, and having high energy density. Furthermore, the DMFC's placement and bending angle have little effect on its performance, suggesting that DMFC is appropriate for flexible portable energy. The flexible all-solid-state DMFC's power density can reach 14.06 mW cm-2 , and after 50 bends at 60°, its voltage loss can be disregarded. The flexible all-solid DMFC has an energy density that is 777.78 Wh Kg-1 higher than flexible lithium-ion batteries, which is advantageous for the commercialization of flexible electronic products.

Hybrid Transition-Metal Oxide and Nitride@N-Doped Reduced Graphene Oxide Electrodes for High-Performance, Flexible, and All-Solid-State Supercapacitors.

Nanoscale composites for high-performance electrodes employed in flexible, all-solid-state supercapacitors are being developed. A series of binder-free composites, each consisting of a transition bimetal oxide, a metal oxide, and a metal nitride grown on N-doped reduced graphene oxide (rGO)-wrapped nickel foam are obtained by using a universal strategy. Three different transition metals, Co, Mo, and Fe, are separately compounded with nickel ions, which originate from the nickel foam, to form three composites, NiCoO2 @Co3 O4 @Co2 N, NiMoO4 @MoO3 @Mo2 N, and NiFe2 O4 @Fe3 O4 @Fe2 N, respectively. These as-prepared active materials have similar regular variation patterns in their properties, including better conductivity and battery-mimicking pseudocapacitance, which result in their high whole-electrode capacitance performance [2598.3 F g-1 (39.85 F cm-2 ), 3472.6 F g-1 (41.43 F cm-2 ) and 1907.5 F g-1 (3.41 F cm-2 ) for the composites incorporating Co, Mo, and Fe, respectively]. The as-assembled flexible, all-solid-state NiCoO2 @Co3 O4 @Co2 N//KOH/PVA//NiCoO2 @Co3 O4 @Co2 N device can be easily bent and exhibits high energy density and power density of 92.8 Wh kg-1 and 1670.4 W kg-1 , respectively. The universality of this design strategy could allow it to be employed in producing hybrid materials for high-performance energy-storage devices.

Electrochromic Os(II)-Based Metallo-Supramolecular Polymers.

This work presents the preparation of a series of novel Os(II)-based metallo-supramolecular polymers (polyOss: linear polyOsL1100% and hyperbranched polyOsL1x% L2y% ) that show a broad absorption spanning 312 to 677 nm and a low Os(II)/(III) redox potential of 0.94 V. The electrochromic properties of a polyOs film cast on an ITO substrate is investigated. The change in transmittance (ΔT) of polyOsL1100% is 49.9%, and the switching times for coloration (t c ) and bleaching (t b ) are 0.70 and 0.82 s, respectively. The introduction of a 10% branching structure (polyOsL190% L210% ) further enhanced the electrochromic performance with ΔT = 59.4%, t c  = 0.41 s, and t b  = 0.54 s. The coloration efficiency (η) increased from 396.1 to 467.5 cm2  C-1 upon branching. A solid-state electrochromic device with polyOsL1100% is successfully fabricated to use the polymer for potential applications.

Ultrahigh energy density realized by a single-layer ß-Co(OH)2 all-solid-state asymmetric supercapacitor.

A conceptually new all-solid-state asymmetric supercapacitor based on atomically thin sheets is presented which offers the opportunity to optimize supercapacitor properties on an atomic level. As a prototype, ß-Co(OH)2 single layers with five-atoms layer thickness were synthesized through an oriented-attachment strategy. The increased density-of-states and 100 % exposed hydrogen atoms endow the ß-Co(OH)2 single-layers-based electrode with a large capacitance of 2028 F g(-1) . The corresponding all-solid-state asymmetric supercapacitor achieves a high cell voltage of 1.8 V and an exceptional energy density of 98.9 Wh kg(-1) at an ultrahigh power density of 17 981 W kg(-1) . Also, this integrated nanodevice exhibits excellent cyclability with 93.2 % capacitance retention after 10 000 cycles, holding great promise for constructing high-energy storage nanodevices.

Molecular Van Der Waals Heterojunction Photodiodes Enabling Dipole-Induced Polarity Switching.

Solid-state devices capable of controlling light-responsive charge transport at the molecular scale are essential for developing molecular optoelectronic technology. Here, a solid-state molecular photodiode device constructed by forming van der Waals (vdW) heterojunctions between standard molecular self-assembled monolayers and two-dimensional semiconductors such as WSe2 is reported. In particular, two non-functionalized molecular species used herein (i.e., tridecafluoro-1-octanethiol and 1-octanethiol) enable bidirectional modulation of the interface band alignment with WSe2 , depending on their dipole orientations. This dipole-induced band modulation at the vdW heterointerface leads to the opposite change of both photoswitching polarity and rectifying characteristics. Furthermore, compared with other molecular or 2D photodiodes at a similar scale, these heterojunction devices exhibit significantly enhanced photo-responsive performances in terms of photocurrent magnitude, open-circuit potential, and switching speed. This study proposes a novel concept of the solid-state molecular optoelectronic device with controlled functions and enhanced performances.

A Tri-Channel Oxide Transistor Concept for the Rapid Detection of Biomolecules Including the SARS-CoV-2 Spike Protein.

Solid-state transistor sensors that can detect biomolecules in real time are highly attractive for emerging bioanalytical applications. However, combining upscalable manufacturing with the required performance remains challenging. Here, an alternative biosensor transistor concept is developed, which relies on a solution-processed In2 O3 /ZnO semiconducting heterojunction featuring a geometrically engineered tri-channel architecture for the rapid, real-time detection of important biomolecules. The sensor combines a high electron mobility channel, attributed to the electronic properties of the In2 O3 /ZnO heterointerface, in close proximity to a sensing surface featuring tethered analyte receptors. The unusual tri-channel design enables strong coupling between the buried electron channel and electrostatic perturbations occurring during receptor-analyte interactions allowing for robust, real-time detection of biomolecules down to attomolar (am) concentrations. The experimental findings are corroborated by extensive device simulations, highlighting the unique advantages of the heterojunction tri-channel design. By functionalizing the surface of the geometrically engineered channel with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody receptors, real-time detection of the SARS-CoV-2 spike S1 protein down to am concentrations is demonstrated in under 2 min in physiological relevant conditions.

Electrochemically Exfoliated Chlorine-Doped Graphene for Flexible All-Solid-State Micro-Supercapacitors with High Volumetric Energy Density.

Graphene-constructed micro-supercapacitors (MSCs) have received considerable attention recently, as part of the prospective wearable and portable electronics, owing to their distinctive merits of well-tunable power output, robust mechanical flexibility, and long cyclability. In the current work, the focus is on the fabrication of high-quality and solution-processible chlorine-doped graphene (Cl-G) nanosheets through a handy yet eco-friendly electrochemical exfoliation process. The Cl-G is characteristic of the large lateral size of ≈10 µm, abundant nanopores with sizes of as small as 2 nm, as well as numerous steps from the rugged surface. Arising from the rich chemical functionalities and structure defects, the all-solid-state MSC built by using Cl-G via a facile mask-assisted method delivers a large reversible capacity and ultrasteady charge/discharge performance, with the capacitance being maintained at 98.1% even after 250 000 cycles. The Cl-G-MSC with EMIMBF4 /PVDF-HFP as the electrolyte displays a large volumetric capacitance up to 160 F cm-3 at the scan rate of 5 mV s-1 and high volumetric energy density of 97.9 mW h cm-3 at the power density of 3.4 W cm-3 . The device can also output a high voltage up to 3.5 V and robust capability with 94.8% of capacitance retention upon 10 000 cycles.

Low-Temperature-Resistant Flexible Solid Supercapacitors Based on Organohydrogel Electrolytes and Microvoid-Incorporated Reduced Graphene Oxide Electrodes.

Maintaining enough flexibility and satisfied electrochemical performance simultaneously at subzero temperatures is still challengeable for flexible solid supercapacitors. In the present work, by adopting an organohydrogel electrolyte and reduced graphene oxide (rGO) films with microvoids serving as electrodes, a supercapacitor, which could be steadily operated down to -60 °C, has been obtained and has shown excellent low-temperature tolerance. The organohydrogel electrolyte consists of LiCl in glycerol/water solution containing polyvinyl alcohol, exhibiting excellent flexibility at -60 °C. Due to the introduction of micropores between rGO sheets, the porous membrane can be folded even in liquid nitrogen. Combining the rGO electrodes with the organohydrogel electrolyte, the maximum voltage of the present supercapacitor could be extended to 2.0 V, and a capacitance of 7.73 F·g-1 at -60 °C could be achieved. After 5000 charge/discharge cycles at -20 °C, the capacitance retention rate is 87.5%. The excellent flexibility and low-temperature resistance of the current supercapacitor pave a novel way for developing compression-resistant electronic samples compatible with a low-temperature environment.