Photo-Stimulated Zn-based Batteries: Progress, Challenges, and Perspectives.

Solar energy, as a renewable energy source, dominates the vast majority of human energy, which can be harvested and converted by photovoltaic solar cells. However, the intermittent availability of solar energy restricts the actual utilization circumstances of solar cells. Integrating photo-responsive electrodes into an energy storage device emerges as a dependable and executable strategy, fostering the creation of photo-stimulated batteries that seamlessly amalgamate the process of solar energy collection, conversion, and storage in one system. Endowed by virtues such as cost-effectiveness, facile manufacturing, safety, and environmental friendliness, photo-stimulated Zn-based batteries have attracted considerable attention. The progress report furnishes a brief overview, summarizing various photo-stimulated Zn-based batteries. Their configurations, operational principles, advancements, and the intricate engineering of photoelectrode designs are introduced, respectively. Through rigorous architectural design, photo-stimulated Zn-based batteries exhibit the ability to initiate charging by saving electricity usage, and in certain instances, even without the need for external electrical grids under illumination. Furthermore, the compensation of solar energy can be explored to improve the output electric energy. At last, opportunities and challenges toward photo-stimulated Zn-based batteries in the process of development are proposed and discussed in the hope of expanding their application scenarios and accelerating the commercialization progress.

Vacancies tailoring lattice anharmonicity of Zintl-type thermoelectrics.

While phonon anharmonicity affects lattice thermal conductivity intrinsically and is difficult to be modified, controllable lattice defects routinely function only by scattering phonons extrinsically. Here, through a comprehensive study of crystal structure and lattice dynamics of Zintl-type Sr(Cu,Ag,Zn)Sb thermoelectric compounds using neutron scattering techniques and theoretical simulations, we show that the role of vacancies in suppressing lattice thermal conductivity could extend beyond defect scattering. The vacancies in Sr2ZnSb2 significantly enhance lattice anharmonicity, causing a giant softening and broadening of the entire phonon spectrum and, together with defect scattering, leading to a ~ 86% decrease in the maximum lattice thermal conductivity compared to SrCuSb. We show that this huge lattice change arises from charge density reconstruction, which undermines both interlayer and intralayer atomic bonding strength in the hierarchical structure. These microscopic insights demonstrate a promise of artificially tailoring phonon anharmonicity through lattice defect engineering to manipulate lattice thermal conductivity in the design of energy conversion materials.

NiFeP nanosheets for efficient and durable hydrazine-assisted electrolytic hydrogen production.

Hydrazine-assisted electrochemical water splitting is an important avenue toward low cost and sustainable hydrogen production, which can significantly reduce the voltage of electrochemical water splitting. Herein, we took a simple approach to fabricate NiFeP nanosheet arrays on nickel foam (NiFeP/NF), which exhibit superior electrocatalytic activity for the hydrogen evolution reaction (HER) and the hydrazine oxidation reaction (HzOR). Our investigations revealed that the excellent electrocatalytic activity of NiFeP/NF mainly arises from the bimetallic synergistic effect, abundant electrocatalytically active sites facilitated by the porous nanosheet morphology, high intrinsic conductivity of NiFeP/NF and strong NiFeP-NF adhesion. We assembled a hydrazine-boosted electrochemical water splitting cell using NiFeP/NF as a bifunctional catalyst for both electrodes, and the overall hydrazine splitting (OHzS) exhibits a considerably low overpotential (100 mV at 10 mA cm-2), and is stable for 40 h continuous electrolysis in a 1 M KOH + 0.5 M N2H4 electrolyte. When it is applied to hydrogen production by seawater electrolysis, its catalytic activity shows strong tolerance. This work provides a promising approach for low cost, high-efficiency and stable hydrogen production based on hydrazine-assisted electrolytic seawater splitting for future applications.

Polynary energy harvesting and multi-parameter sensing in the heatwave environment of industrial factory buildings by an integrated triboelectric-thermoelectric hybrid generator.

Taking advantage of a hybrid generator to simultaneously collect polynary energy from a single energy source provides a feasible solution for the energy dilemma in the new era. Herein, we integrate a triboelectric nanogenerator and a thermoelectric generator for polynary energy harvesting and self-powered sensing of heatwaves in large-scale industrial factory buildings, which contains both thermal energy and wind energy. The new design of the fan-shaped rotation triboelectric nanogenerator (FR-TENG) makes it more compact and easily integrated. After structure modeling, the energy conversion efficiency of the FR-TENG can reach a maximum of 37.2%, which can successfully power a Bluetooth hygrothermograph transmitting environmental information wirelessly every 30 s at a wind speed of 4.67 m s-1. An all-inorganic flexible thermoelectric generator (iThEG) is developed based on copper and constantan with an output power density of 0.73 W m-3, and maintains its original mechanical properties after 10 000 bending tests. Moreover, a self-powered hot wind sensing system based on Labview is established which can display wind-speed and wind-temperature in real time. The working concept presented here is also applicable to other single energy sources containing multiple energy forms, such as falling raindrops and sunlight, which can lift energy utilization and conversion efficiency and alleviate the energy crisis.

Synchronous coupling of defects and a heteroatom-doped carbon constraint layer on cobalt sulfides toward boosted oxide electrolysis activities for highly energy-efficient micro-zinc-air batteries.

The sluggish kinetics of oxygen electrocatalysis reactions on cathodes significantly suppresses the energy efficiency of zinc-air batteries (ZABs). Herein, by coupling in situ generated CoS nanoparticles rich in cobalt vacancies (VCo) with a dual-heteroatom-doped layered carbon framework, a hybrid Co-based catalyst (Co1-xS@N/S-C) is designed and synthesized from Co-MOF precursor. Experimental analyses, together with density functional theory (DFT)-based calculations, demonstrate that the facilitated ion diffusion enabled by the introduced VCo, together with the enhanced electron transport benefiting from the well-designed dual-heteroatom-doped laminated carbon framework, synergistically boost the bifunctional electrocatalytic activity of Co1-xS@N/S-C (ΔE = 0.76 V), which is much superior to that of CoS@N/S-C without VCo (ΔE = 0.89 V), CoS without VCo (ΔE = 1.23 V), and the dual-heteroatom-doped laminated carbon framework. As expected, the further assembled ZAB employing Co1-xS@N/S-C as the cathode electrocatalyst exhibits enhanced energy efficiency in terms of better cycling stability (510 cycles/170 hours) and a higher specific capacity (807 mA h g-1). Finally, a flexible/stretched solid state micro-ZAB (F/SmZAB) with Co1-xS@N/S-C as the cathode electrocatalyst and a wave-shaped GaIn-Ni-based liquid metal as the electronic circuit is further designed, which can display excellent electrical properties and long elongation. This work provides a new defect and structure coupling strategy for boosting the oxide electrolysis activities of Co-based catalysts. Furthermore, F/SmZAB represents a promising solution for a compatible micropower source in wearable microelectronics.

Solar-Light-Responsive Zinc-Air Battery with Self-Regulated Charge-Discharge Performance based on Photothermal Effect.

It is extremely challenging to significantly increase the voltaic efficiency, power density, and cycle stability of a Zn-air battery by just adjusting the catalytic performance of the cathode with nanometers/atomistic engineering because of the restriction of thermodynamic equilibrium potential. Herein, inspired by solar batteries, the S-atom-bridged FeNi particles and N-doped hollow carbon nanosphere composite configuration (FeNi-S,N-HCS) is presented as a prototype of muti-functional air electrode material (intrinsic electrocatalytic function and additional photothermal function) for designing photoresponsive all-solid-state Zn-air batteries (PR-ZABs) based on the photothermal effect. The local temperature of the FeNi-S,N-HCS electrode can well respond to the stimuli of sunlight irradiation because of their superior photothermal effect. As expected, under illumination, the power density of the as-fabricated PR-ZABs based on the FeNi-S,N-HCS electrode can be improved from 77 mW cm-2 to 126 mW cm-2. Simultaneously, charge voltage can be dramatically reduced, and cycle lifetime is also prolonged under illumination, because of the expedited electrocatalytic kinetics, the increased electrical conductivity, and the accelerated desorption rate of O2 bubbles from the electrode. By exerting the intrinsic electrocatalytic and photothermal efficiency of the electrode materials, this research paves new ways to improve battery performance from kinetic and thermodynamic perspectives.

Nonsteroidal anti-inflammatory drug monitoring in serum: a Tb-MOF-based luminescent mixed matrix membrane detector with high sensitivity and reliability.

The identification of drugs or biomolecules for public health monitoring requires facile analytical technologies with excellent sensitivity, portability and reliability. In the past decades, different sensing materials have inspired the development of various bioanalytical strategies. However, sensing platforms based on powder materials are not suitable for medical diagnosis, which limits further exploration and application of biosensors. Herein, a point-of-care testing (POCT) membrane was designed from an energy competition mechanism and achieved the detection of the nonsteroidal antiphlogistic diclofenac, and exhibited remarkable testing efficacy at the ppb level. The mixed matrix membrane (MMM) sensor consists of electrospun polyacrylonitrile nanofibers and luminescent Tb-MOFs and possess the advantages of high stability, outstanding anti-interference ability, efficient detection (LOD = 98.5 ppb) and easy visual recognition. Furthermore, this MMM sensor exhibits excellent recyclability in serum, which is beneficial for developing a portable and convenient device to distinguish diclofenac in practical sensing applications. Meanwhile, the feasibility and mechanism of this recyclable sensor were verified by theory and experiments, indicating that it is a promising device for diclofenac detection in biological environments to evaluate the toxic effect caused by the accumulation of nonsteroidal drugs.

Biaxial Stretching Array Based on High-Energy-Efficient MXene-Based Al-Ion Micro-supercapacitor Island and Editable Stretchable Bridge.

Employment of multivalent charge carriers with higher charge density to replace frequently used univalent ones can effectively increase the areal capacitance of micro-supercapacitors utilizing few-layered MXene self-assembled electrodes. However, their larger charge density and ionic size usually lead to a sluggish extraction/insertion dynamic between MXene interlayers with limited free space, greatly offsetting the benefits. Herein, we show how to facilitate de-/intercalation of high-valence charge carriers (Al3+) by using polypyrrole-coated bacterial cellulose (BC@PPy) nanospacers to expand MXene interlayer space. Together with the longitudinal electron transport path between interlayers synchronously constructed by the conductive PPy shell, a significant 496% areal capacitance enhancement (232.79 mF cm-2) is realized in the fabricated symmetric Al3+-ion micro-supercapacitors (AMSCs) with the obtained MXene/BC@PPy hybrid film electrodes employing polyacrylamide/1 M AlCl3·6H2O hydrogel electrolyte relative to the cell with pure MXene film electrodes (39.02 mF cm-2). Further benefiting from a high output voltage of 1.2 V, the AMSCs acquire an areal energy density up to 45.3 µW h cm-2. As a device demonstration, we further fabricate a biaxially stretchable AMSC array, simulate its spatial strain distribution during biaxial stretching, and characterize its electrochemical and mechanical properties up to an extreme areal strain of 300%. The proposed rational fabrication paradigm achieves a new level of combined energy density, stretch performance, and architectural simplicity, which presents a route toward a commercially viable stretchable micro energy-storage system with high energy efficiencies.

Natural Polysaccharide Strengthened Hydrogel Electrolyte and Biopolymer Derived Carbon for Durable Aqueous Zinc Ion Storage.

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) represent one of the current research subjects because of their flame retardancy, ease of manufacturing, and exceptional roundtrip efficiency. With the evolution into real useful energy storage cells, the bottleneck factors of the corrosion and dendrite growth problems must be properly resolved for largely boosting their cycling life and energy efficiency. Herein, a natural polysaccharide strengthened hydrogel electrolyte (denoted as PAAm/agar/Zn(CF3SO3)2) was engineered by designing an asymmetric dual network of covalently cross-linked polyacrylamide (denoted as PAAm) and physically cross-linked loose polysaccharide (e.g., agar) followed by intense uptake of Zn(CF3SO3)2 aqueous electrolyte. In this polymeric matrix, the PAAm chains are responsible for constructing the soft domains to immobilize the water molecules, and the agar component boosts the mechanical performance (by using its inherent reversible sacrificial bonds) and favors the electrolyte ion transport. Due to these reasons, the as-designed hydrogel electrolyte effectively inhibits the zinc dendrite growth, realizes the uniform Zn deposition, and affords a satisfactory ionic conductivity of 1.55 S m-1, excellent tensile strength (78.9 kPa at 507.7% stretchable), and high compression strength (118.0 kPa at 60.0% strain). Additionally, a biopolymer-derived N-doped carbon microsphere cathode material with a highly interconnected porous carbonaceous network (denoted as NC) was also synthesized, which delivers a high capacity of 92.8 mAh g-1, along with superb rate capability and long duration cycling lifespan (95.4% retention for 10000 cycles) in the aqueous Zn//NC ZHSC. More notably, with integrated merits of the PAAm/agar/Zn(CF3SO3)2 hydrogel electrolyte and NC, the as-built quasi-solid-state ZHSC achieves a high specific capacity of 73.4 mAh g-1 and superior energy density of 61.3 Wh kg-1 together with excellent cycling stability for 10000 cycles. This work demonstrated favorable practicability in the structural design of the hydrogel electrolytes and electrode materials for advanced ZHSC applications.

Hydrophobization Engineering of the Air-Cathode Catalyst for Improved Oxygen Diffusion towards Efficient Zinc-Air Batteries.

Poor oxygen diffusion at multiphase interfaces in an air cathode suppresses the energy densities of zinc-air batteries (ZABs). Developing effective strategies to tackle the issue is of great significance for overcoming the performance bottleneck. Herein, inspired by the bionics of diving flies, a polytetrafluoroethylene layer was coated on the surfaces of Co3 O4 nanosheets (NSs) grown on carbon cloth (CC) to create a hydrophobic surface to enable the formation of more three-phase reaction interfaces and promoted oxygen diffusion, rendering the hydrophobic-Co3 O4 NSs/CC electrode a higher limiting current density (214 mA cm-2 at 0.3 V) than that (10 mA cm-2 ) of untreated-Co3 O4 NSs/CC electrode. Consequently, the assembled ZAB employing hydrophobic-Co3 O4 NSs/CC cathode acquired a higher power density (171 mW cm-2 ) than that (102 mW cm-2 ) utilizing untreated-Co3 O4 NSs/CC cathode, proving the enhanced interfacial reaction kinetics on air cathode benefiting from the hydrophobization engineering.

Synergetic Chemistry and Interface Engineering of Hydrogel Electrolyte to Strengthen Durability of Solid-State Zn-Air Batteries.

For the challenging pursuit of high energy efficiency and mechanical tolerance in flexible solid-state Zn-air batteries (FSZABs), a hydrogel electrolyte (HE) consisting of dual-network crosslinked polyacrylic acid-Fe3+ -chitosan (PAA-Fe3+ -CS) polymer host infiltrated with a mixed aqueous electrolyte of NH4 Cl and ZnCl2 is developed. The absorbed near-neutral electrolyte renders the HE high ionic conductivity but low corrosiveness to both electrocatalysts and Zn metal anode (ZMA), ensuring more stable Zn-OH-O2 chemistry compared to that in strong alkaline electrolyte and thus endowing the assembled FSZABs with a landmark cycle life up to 120 h (5 mA cm-2 ). More intriguingly, the CS molecular beams introduced into the PAA hydrogel backbone will precipitate and fold subjecting to the Hofmeister effect when saturated with the near-neutral electrolyte, which can effectively enhance the interfacial adhesion strength of the HE on both air cathode and ZMA, achieving reliable and robust bonding between them. Thus, the FSZABs simultaneously exhibited a superior tolerance to repeated mechanical deformation during operation, allowing more than 360 continuous bending-recovery cycles without any decline in voltage efficiency. The ingenious chemistry and interface synergetic engineering on the crucial HEs provides a rational methodology to realize boosted electrochemical and mechanical durability of FSZABs forward for future practical implementation.

Ion Sieve: Tailoring Zn2+ Desolvation Kinetics and Flux toward Dendrite-Free Metallic Zinc Anodes.

Tip-induced dendrites on metallic zinc anodes (MZAs) fundamentally deteriorate the rechargeability of aqueous Zn metal batteries (ZMBs). Herein, an intriguing ion sieve (IS) consisting of 3D intertwined bacterial cellulose, deposited on the surface of MZAs (Zn@IS) through an in situ self-assembly route, is first presented to be effective in inhibiting dendrite-growth on MZAs. Experimental analyses together with theoretical calculations suggested that the IS coating can facilitate the desolvation of [Zn(H2O)6]2+ clusters via a strong interplay with Zn ions, weaken hydrogen evolution reaction of MZAs, and homogenize the ion flux with the abundant nanopores serving as ion tunnels, synergistically enabling dendrite-free Zn deposition on the Zn@IS anodes. Consequently, a lifespan up to 3000 h at a cutoff capacity of 0.25 mA h cm-2 was observed in a Zn@IS∥Zn@IS symmetric cell. In terms of application, pairing with a carbon-nanotube@MnO2 cathode as an example, the full ZMBs acquired enhanced rechargeability with much higher capacity retention over 73.3% after 3000 cycles compared to the counterpart with pristine MZA (21%).

A mild reduction of Co-doped MnO2 to create abundant oxygen vacancies and active sites for enhanced oxygen evolution reaction.

Efficient and non-precious-metal-based catalysts (e.g., manganese-based oxides) for the oxygen evolution reaction (OER) remain a substantial challenge. Creation of oxygen vacancies of manganese-based oxides with the aim to enhance their intrinsic activities is rarely reported, and there is a critical requirement for a mild and facile synthesis strategy to create abundant oxygen vacancies on manganese-based oxides. Herein, Co-doped MnO2 nanowires were reduced by NaBH4 solution at room temperature; then, MnCo2O4.5 nanosheets with abundant oxygen vacancies and active sites were formed on the surface of Co-doped MnO2 nanowires. Benefiting from the reduction strategy, the fabricated hierarchical Co-doped-MnO2@MnCo2O4.5 nanowire/nanosheet nanocomposites exhibit higher catalytic activity (an overpotential of 250 mV at a current density of 10 mA cm-2 in 1.0 M KOH solution) than pristine Co-doped MnO2 nanowires. The calculated TOF of Co-doped-MnO2@MnCo2O4.5 is 0.034 s-1 at the overpotential of 300 mV, which is 136-fold higher than that of Co-doped-MnO2. The excellent OER performance was attributed to the synergistic advantages of abundant oxygen vacancies and active sites over the hierarchical nanowire-nanosheet architectures.

Hydrogel Electrolytes for Quasi-Solid Zinc-Based Batteries.

On account of high energy density depending on the utilized zinc metal anode of high theoretical capacity and its excellent security due to aqueous electrolytes that usually be locked in polymer hosts referred to as hydrogels, quasi-solid zinc-based batteries have been subjected to more and more interest from researchers. The good water retention and electrolyte load capacity of the hydrogel, contributing to the acquirement of high ionic conductivity and durability of the as-obtained quasi-solid electrolyte, play a significant role on the performance of the devices. Moreover, the chemistry of hydrogels can be tuned to endow quasi-solid electrolytes with additional functions in terms of application scenarios of solid-state batteries. Herein, the frontier disciplines of hydrogel electrolytes for Zn-based batteries were reviewed. The cross-linking process of the polymer networks for hydrogel materials with different functions, such as stretchability, compressibility, and self-healing, were also discussed to analyze the properties of the polymer electrolyte. Based on the merits of the functionalized hydrogel, the further application of hydrogel electrolytes in Zn-based batteries is the focus of this paper. The electrochemical performance and mechanical property of Zn-based batteries with functionalized hydrogel electrolytes under extreme conditions were presented to evaluate the crucial role of the polymer hydrogel electrolyte. Finally, the challenges of hydrogel electrolytes for currently developed Zn-based batteries are highlighted with the hope to boost their commercial application in energy conversion devices.

Concurrently Realizing Geometric Confined Growth and Doping of Transition Metals within Graphene Hosts for Bifunctional Electrocatalysts toward a Solid-State Rechargeable Micro-Zn-Air Battery.

The simultaneous realization of confined growth and doping of transition metals within carbon hosts promises to deliver unusual bifunctional catalytic activity but still remains challenging due to the difficulty in achieving synchronous nucleation and diffusion of metallic ions in a single synthesis step. Herein, we present a simple synthesis strategy capable of concurrently realizing geometric confined growth and doping of transition metals within graphene hosts, demonstrated in Co,N-codoped graphene-confined FeNi nanoparticles (Co,N-GN-FeNi). The obtained Co,N-GN-FeNi can take full advantage of the hierarchy of interactions between the confined-grown FeNi nanoparticles (for high oxygen evolution reaction (OER) activity) and the Co,N-codoped graphene hosts (for high oxygen reduction reaction (ORR) activity). The overall structure is a rationally designed synergy that simultaneously realizes (i) adequate exposure of electroactive sites, (ii) effective protection against corrosion/aggregation of FeNi nanoparticles, and (iii) rapid transport of ions/electrons between the interfaces. As a result, Co,N-GN-FeNi exhibits excellent bifunctional electrocatalytic activity relying on a low ORR/OER subtraction (ΔE = 0.81 V). Subsequent combination with a planar electrode configuration and a solid polymer electrolyte further demonstrates the utilization of Co,N-GN-FeNi as air cathode bifunctional electrocatalysts in a solid-state rechargeable micro-Zn-air battery (SR-MZAB), which exhibits a large open-circuit voltage of 1.39 V, a high power density/specific capacity of 62.3 mW cm-2/763 mAh g-1, excellent durability (126 cycles/42 h), and mechanical flexibility. This work demonstrates an effective synthesis strategy for concurrently realizing geometric confined growth and doping of transition metals within carbon hosts, for enhanced bifunctional catalytic activity toward novel SR-MZABs with high energy efficiency, security, and flexibility for wearable micropower sources.

A novel self-assembled-derived 1D MnO2@Co3O4 composite as a high-performance Li-ion storage anode material.

Manganese dioxide (MnO2) is a high-performance anodic material and applied widely in lithium-ion batteries (LIBs). However, some intrinsic limitations originate from the low ionic conductivity, high polarization, and severe volume expansion of this type of material. In this work, we generated a one-dimensional porous MnO2@Co3O4 composite from a MnOOH@ZIF-67 precursor, which is synthesized via a self-assembly strategy. The one-dimensional porous structure provided more active sites and shorter-ion/electron-diffusion distance, thereby enabling higher Li+ storage capacity and better rate capability than a transition metal oxide alone. The Co3O4 coating buffered the volume change during Li+ insertion/extraction, leading to increased cycling stability of the electrode. When evaluated as the anode of LIBs, MnO2@Co3O4 exhibited a reversible capacity of 647 mA h g-1 at 2000 mA g-1 after 400 cycles. This excellent performance indicated that the MnO2@Co3O4 material could be an attractive potential candidate for Li+ storage.

Pollen-derived porous carbon decorated with cobalt/iron sulfide hybrids as cathode catalysts for flexible all-solid-state rechargeable Zn-air batteries.

The development of flexible all-solid-state rechargeable Zn-air batteries (FS-ZABs) for wearable applications faces challenges from the balance between performance and flexibility of the battery; efficient cathode catalyst and reasonable electrode construction design are key factors. Herein, a low-cost pollen derived N,S co-doped porous carbon decorated with Co9S8/Fe3S4 nanoparticle hybrids (Co-Fe-S@NSRPC) has been synthesized. Owing to the active Co9S8/Fe3S4 nanoparticles, N,S co-doping, and large specific area of the pollen derived porous carbon matrix, the Co-Fe-S@NSRPC composite exhibits an excellent bifunctional catalytic activity with a small potential gap (ΔE = 0.80 V) between the half-wave potential for the ORR (0.80 V) and the potential at 10 mA cm-2 for the OER (1.60 V), and endows a liquid Zn-air battery with a high power density of 138 mW cm-2, a larger specific capacity of 891 mA h g-1 and a stable rechargeability of up to 331 cycles. Based on the Co-Fe-S@NSRPC cathode catalyst, a 2D coplanar FS-ZAB has been fabricated with specially designed parallel narrow strip electrodes alternately arrayed on a polyacrylamide polyacrylic acid copolymer hydrogel solid electrolyte. The presented FS-ZAB exhibits excellent battery performance with high open-circuit-voltage (1.415 V), competitive peak power density (78 mW cm-2), large specific capacity (785 mA h g-1) and stable rechargeability (150 cycles), offers robust flexibility to maintain stable charge/discharge capacity under different bending deformations, and provides convenient coplanar integrability to realize parallel or series connection of multiple cells in a relatively small area.

N-Doped-carbon/cobalt-nanoparticle/N-doped-carbon multi-layer sandwich nanohybrids derived from cobalt MOFs having 3D molecular structures as bifunctional electrocatalysts for on-chip solid-state Zn-air batteries.

The unsatisfactory energy efficiency and leakable liquid electrolytes in conventional Zn-air batteries with intrinsic semi-open structures greatly limit their opportunity to be a safe micropower source for flexible/wearable electronics. Herein, N-doped-carbon/cobalt-nanoparticle/N-doped-carbon (NdC-CoNP-NdC) multi-layer sandwich nanohybrids were first synthesized via the pyrolysis of a well-designed Co-MOF precursor with a 3D molecular framework. Profiting from the synergistic effect enabled by the interlayer-confined growth of monodispersed cobalt nanoparticles having high activity/stability and a thousand-layer-cake porous N-self-doped carbon skeleton of high conductivity and additional active sites as well as the reasonable design of a multi-layer sandwich interface structure between them that acts as an interconnected nanoreactor, the as-obtained NdC-CoNP-NdC multi-layer sandwich nanohybrids exhibit excellent bifunctional catalytic activity of a small ORR/OER gap (0.83 V). We followed a planar electrode configuration design with an interdigital carbon cloth coated with NdC-CoNP-NdC as the air cathode and an interdigital Zn foil as the metal anode as well as the introduction of a polyacrylamide-co-polyacrylic/6 M KOH alkaline gel as an incombustible solid-state electrolyte. Thus, on-chip all-solid-state rechargeable Zn-air batteries (OAR-ZABs) are further developed, achieving a cycle life up to 150 cycles per 50 h, high power density/specific capacity as much as 57.0 mW cm-2/771 mA h g-1, respectively, and excellent coplanar integration capability and mechanical flexibility for working steadily under bending deformation. Eventually, as an additional advancement, an autonomous smartwatch powered by the coplanar integrated OAR-ZABs is demonstrated, which possesses excellent integrity and flexibility and is comfortably wearable for timing and step counting dynamically; this demonstrates the successful application of assembling OAR-ZABs into highly integrated wearable electronics as a compatible micropower source.

Quantum dot embedded N-doped functionalized multiwall carbon nanotubes boost the short-circuit current of Ru(ii) based dye-sensitized solar cells.

Here, we report zinc sulfide quantum dots, ZnS(QDs), moored on N-doped functionalized multiwall carbon nanotubes (MWCNTs) wrapped with reduced graphene oxide (rGO). The MWCNTs have a tangled network, a particular surface area, and a distinctive hollow structure that may be suitable for use as a counter electrode (CE) material. A ZnS@N.f-MWCNTs@rGO composite as the CE on a fluorine-doped tin oxide substrate in a dye-sensitized solar cell (DSSC) was fabricated using a doctor blade technique. The electrochemical performance showed that at the electrolyte/CE interface, the ZnS(QDs) and N-doped functionalized MWCNTs wrapped with rGO (ZnS@N.f-MWCNTs@rGO) electrode has a lower transfer charge resistance (Rct) and a greater catalytic capacity than naked ZnS(QDs). A power conversion efficiency (PCE) of 9.4% was attained for this DSSC gadget, which is higher than that of a DSSC gadget utilizing ZnS(QDs), ZnS@N.f-MWCNTs, ZnS@rGO and Pt. Also, the DSSC device using ZnS@N.f-MWCNTs@rGO had a fill factor (FF) that was better than the other counter electrodes. The cyclic voltammetry and electrochemical impedance spectra (EIS) electron transfer measurements showed that ZnS@N.f-MWCNTs@rGO films can provide fast electron transfer from the electrolyte to the CE and great electrocatalytic activity to reduce triiodide to a CE based on ZnS@N.f-MWCNTs@rGO in the DSSC.

The Synergistic Effect Accelerates the Oxygen Reduction/Evolution Reaction in a Zn-Air Battery.

Perovskite oxides are promising electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to their abundance and high intrinsic catalytic activity. Here we introduce Ag into Sm0.5Sr0.5CoO3-δ (SSC) to form a Ag-SSC catalyst by ultrasonication and apply it as the air electrode for a Zn-air battery. It finds that the introduction of Ag into SSC can transform the Ag-SSC into a good bifunctional electrocatalyst toward ORR as well as OER. For instance, a more active half-wave potential with a value of 0.76 V for ORR is obtained at 1,600 rpm, while the OER overpotential is 0.43 V at I = 10 mA cm-2. Further characterization demonstrates that the improved catalyst activity of the Ag-SSC can be assigned to the synergistic effect generated between the Ag and SSC phases. The Zn-air battery with the Ag-SSC as an electrode not only gives a same discharge-charge voltage gap (1.33 V) with that of commercial Pt/C (1.33 V) but also presents an equivalent current efficiency (45.7% for Ag-SSC and 45.3% for Pt/C) at 10 mA cm-2. Moreover, the stability for 110 cycles is better. This result indicates that the Ag-SSC catalyst shows promise for use as a bifunctional electrocatalyst toward OER and ORR.