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With the rapid development of portable/wearable electronic devices, the demand for highly efficient and sustainable self-powered systems to support their off-grid operation has risen considerably. Recently, metal halide perovskites (MHPs) have been suggested as promising materials for energy harvesting and storage devices because of their excellent optoelectronic, ferro/piezoelectric, and ion migration properties. However, the high toxicity and poor physicochemical stability of MHPs hamper their practical application. Herein, for the first time, the potential of methylammonium tin halide (MA 2 SnX 6 ; X = Cl, Br, and I) double perovskite thin films for high-efficiency self-charging power units (SPUs) is elucidated by virtue of their high stability in air. To this end, the integration of an MA 2 SnCl 6 -based piezoelectric nanogenerator (PENG) with a lithium metal battery (LMB), which also uses an MA 2 SnCl 6 -based thin film as the cathode, is demonstrated. The MA 2 SnCl 6 -based PENG exhibited a high output power density of 7.33 μW cm−2 and an excellent mechanical durability. Furthermore, MA 2 SnCl 6 as a cathode in LMB recorded the highest specific capacity of 589.98 mAh g−1. A 1 nm-thick Al 2 O 3 coating on the MA 2 SnCl 6 surface improved the capacity retention from 16.9 % to 75.1 % for 100 cycles, indicating its stable performance. The MA 2 SnCl 6 -based LMB is charged by the MA 2 SnCl 6 -based PENG and utilized as an SPU for operating various small-scale electronics (humidity meter, calculator, and LED). This work not only demonstrates the feasibility of MHPs toward high-capacity batteries and energy harvesters but also provides insights into the general design principles of MHP-based devices. [Display omitted] • Lead-free MA 2 SnX 6 double halide perovskite as an active material for efficient energy harvester and storage device. • MA 2 SnCl 6 -based PENG exhibited a high output power density of 7.33 μW cm−2. • MA 2 SnCl 6 -based Li metal battery recorded the highest specific capacity of 589.98 mAh g−1. • Improved capacity retention of MA 2 SnCl 6 -based LMB by the Al 2 O 3 surface coating. • Realizing of self-charging power unit by combing MA 2 SnCl 6 -based Li metal battery and PENGs. [ABSTRACT FROM AUTHOR]

The configuration of reinforced composite membrane (RCM), composed of porous polytetrafluoroethylene (PTFE) as a mechanical reinforcement and perfluorosulfonic acid (PFSA) as a proton conductive polymer, has gained a large interest due to its promisingly high performance for polymer electrolyte membrane (PEM) fuel cells. However, the inaccessible polymeric nanocomposites in preparing RCMs are still faced with critical challenges associated with immiscible interactions between hydrophilic sulfonate groups in PFSA and the hydrophobic nanoporous PTFE matrix. Herein, we report a well-refined and facile fabrication strategy for producing a cross-aligned PTFE (CA-PTFE) framework. The electric-field guided electrospinning enables the creation of unique micron-scale, grid-type PTFE matrix, which is synthesized by annealing of electrospun conjugated polymers, resulting in the removal of carrier polymer and the formation of continuous fibrious structure via fusion of PTFE particles. The CA-PTFE RCM embodying uniformly impregnated PFSA in a grid-type PTFE matrix, facilitates hydration of the membranes, with minimal swelling and efficient diffusion of protons through concentrated sulfonate groups. The CA-PTFE RCM adopted cell showed outstanding fuel cell currents during both low and high humidity operation, with a current density of 1.38 A cm−2 at 0.6 V and maximum power density of 0.85 W cm−2 under RH 100% condition. Furthermore, the CA-PTFE RCM was able to achieve a long-lasting single-cell operation with a significantly low hydrogen crossover (less than 5 mA cm−2 at 0.4 V) even after 21,000 wet/dry cycles, which surpasses the standard of membrane durability for transportation application. The rational design of fibrous PTFE reinforcements opens up new engineering opportunities for the future development of high-stability PEM fuel cells. [Display omitted] • Cross-aligned PTFE (CA-PTFE) framework is synthesized via electric-field guided electrospinning and subsequent calcination. • As a reinforcement, micron-scale patterned CA-PTFE framework is beneficial for the PFSA impregnation and the proton conduction. • CA-PTFE reinforced composite membrane shows the outstanding current density and exceptional durability in PEM fuel cells. [ABSTRACT FROM AUTHOR]

Hydro-electric technology has gathered much attention by the virtue of water as the energy source. However, the low energy density of this technology severely limits its practical use. Here, we demonstrate a PEDOT:PSS-based transpiration-driven electrokinetic power generator (p-TEPG) that enables the utilization of a wider variety of real-world water resources for maximizing energy generation efficiencies. In addition to the conventional electrical double layer on the material surface, the p-TEPG builds an additional potential difference in the polymer matrix by the selective penetration of cations into the matrix that contains sulfonate functional groups. p-TEPG exhibits 80–250% higher energy density than carbon-based TEPG at the same resistance. Moreover, seawater produced enhanced volumetric energy/power densities (34.36 mJ cm−3 and 44.70 μW cm−3) and areal energy/power densities (410 μJ cm−2 and 0.45 μW cm−2), respectively, compared to DI water on a single p-TEPG device, which is sufficient to charge electrical energy storage systems and directly operate low-powered electronic. • p-TEPG maximizes energy harvesting efficiency by ion-permselective PEDOT:PSS. • Green water resources improve performance of p-TEPG. • p-TEPG adsorbs more cations into its polymer matrix by sulfonate groups. • p-TEPG can increases energy harvesting efficiency by using anions and cations with smaller radii. • p-TEPG can be fueled with seawater, demonstrating its potential for blue energy generating system. [ABSTRACT FROM AUTHOR]

Silicon-coated molybdenum sulfide nanosheets were prepared in a thin-film shape (Si–MoS 2 TFs) through metal organic chemical vapor deposition (MOCVD) and radio frequency (RF) sputtering. By using MOCVD, the MoS 2 thin films composed of nanosheets were vertically grown on stainless steel substrates. To address the problem of polysulfide dissolution and shuttling effect of MoS 2 during discharge and charge reactions in thin-film Li-ion batteries, the entire surfaces of MoS 2 TFs were covered with silicon layers using RF sputtering. Compared with pristine MoS 2 TFs without protection, the Si–MoS 2 TFs showed excellent reversibility with a high capacity of ∼2000 mAh g−1 for 500 cycles in thin-film Li-ion batteries. Both materials – MoS 2 and Si – were synergistically taken into account to enhance the ability to store Li ions in the host structures and complement each other during repeated conversion and alloying reactions. The underlying reaction principle was elucidated, which provides insight into developing MoS 2 -based thin-film cathodes. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrodeposition and electropolymerization have emerged as versatile tools for the fabrication of chemical and biosensors. The literature in this area, published since 2017, is the main focus of this review. Electropolymerization has played a particularly prominent role in sensor development since its discovery in 1980 by Diaz at IBM. The ability to entrain receptors such as antibodies, engineered virus particles, and metal chelating agents into a conductive polymer sensing element during electropolymerization has proven to be a powerful means of preparing chemiresistors for a variety of analyses. Electrodeposition has also been used to prepare nanostructured metal indicator microelectrodes, enabling of a new modality for transducing biosensors. Electrodeposited metal nanowires have formed the basis for rapid and sensitive sensors for hydrogen gas. Electrodeposition has also been exploited as a powerful means for amplifying weak biosensor signals, extending their dynamic range. Opportunities for the application of electrodeposition and electropolymerization for chemical and biological sensor fabrication and function are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] van der Waals heterostructures (vdWHs), consisting of more than one type of atomically thin 2D crystal layers are emerging platforms for interesting electrical, optical, and catalytic applications. High yield production of vdWHs with atomic scale precision is crucial prerequisite for practical utilization. Here we present a generalized approach of random solution phase, high yield heteroassembly of semiconducting vdWHs by exploiting inherent surface charge states of 2D materials as well as chemical affinity of specific ligand end-functionalities. Facile removal of noncovalent functionalized ligands via simple pH reversal enables clean interfaces within vdWHs, yielding outstanding optoelectrical and electrochemical properties driven by fluent interfacial charge transfer among the layered 2D structures. The generality of this procedure is demonstrated by the formation of a series of different vdWHs such as WSe 2 -MoS 2 , graphene–MoS 2 - and phospherene–WSe 2 heterostructures. Atomically thin WSe 2 –MoS 2 phototransistor displayed an exceptionally fast response time with high sensitivity. Graphene–MoS 2 overcomes the inherent charge transfer issue of MoS 2 for electrochemical catalyst. Phospherene–WSe 2 successfully addresses poor ambient stability of phospherene together with enhanced surface activity towards chemical sensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple but powerful solution to overcome the chronic bottleneck of the nanocatalyst delivery on oxide support: the carbothermal shock driven nanocatalyst formation on carbon nanofibers (CNFs) with small sizes and fine distribution can be delivered to oxide structures of choice while retaining high uniformity. • Fabrication of catalyst delivered porous oxide structures: the asymmetric sputtering of oxide on CNFs can induce the formation of openly porous hemi-tubular structures with tunable porosity and thickness. A simple subsequent calcination results in the transfer of catalysts from the CNF template to the porous oxide structures. • Superior hydrogen sulfide sensing properties: Uniform distribution of Pt nanoparticles on SnO 2 hemitubes showed superior H 2 S sensing performances (Response Rair/Rgas > 1500 at 5 ppm H 2 S) compared to state-of-the-art H 2 S sensors. To achieve powerful gas sensors oxide semiconductor chemiresistors, the uniform functionalization of nanocatalysts on the desired metal oxides is considered as a key strategy. However, still, it is challenging to achieve the nanocatalysts decoration on desired oxides without deterioration of target materials. In this study, thermal-shock (rapid joule-heating method) was applied to uniformly decorate Pt nanoparticles (NPs) on the surface of carbon nanofibers (CNFs) to achieve the uniform distribution of Pt NPs on one-dimensional structures. And then, SnO 2 was physically deposited on the Pt NPs loaded CNFs and continuous heat-treatment was conducted to transfer the Pt NPs to desired SnO 2 porous hemitubes. Thanks to the well-distributed Pt NPs on porous SnO 2 hollow structures, the Pt laoded SnO 2 hemitubes showed an exceptional sensitivity (R air /R gas = 1500 at 5 ppm) in H 2 S. Also, it showed high selectivity for H 2 S and high stability even under continuous gas exposure, confirming its potential as an effective H 2 S sensor. [ABSTRACT FROM AUTHOR]

• Synthesis of CA-CNF by insulating block electrospinning & carbonization. • Formation of cross-aligned network even after heat treatment. • Faster reaction kinetics and regular electron pathway of CA-CNF. • High-rate cyclability of CA-CNF (259.4 mAh g−1 at 3000 mA g−1). The conventional use of metallic current collector in an electrochemical cell results in decreased loading of active materials and hence limited capacity in consideration of all the inactive current collector components. In response to this trend, a number of conductive, free-standing materials have been proposed as electrodes, which would act as both current collector and active materials. Here, in this study, we have firstly developed the cross-aligned carbon nanofiber (CA-CNF) for efficient Li storage, especially at high current densities. Using the insulating block electrospinning, the nanofibers can be aligned in a certain direction, where it is viable to fabricate cross-aligned nanofibers in a cost-effective and scalable manner. Attributed to faster kinetics and regular electron pathway arising from CA-CNF, it exhibits an excellent high-rate cyclability (259.4 mAh g−1 at a current density of 3000 mA g−1). This work builds up a milestone in suggesting a cross-aligned carbon nanofibrous network as efficient Li storage, which can also be applied to various electrode materials embedded cross-aligned conductive composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]