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Rechargeable zinc–air batteries (ZABs) is primarily driven by the couple of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Currently, it is still challenging to develop cost-effective, highly efficient, and robust bifunctional catalysts for ZABs. Herein, a novel silver decorated cobalt carbonate (Ag@CoCO3) hybrid catalyst is proposed as the potential bifunctional catalyst to drive OER and ORR for ZABs. Engineering Ag nanoparticles onto the surface of CoCO3 microsphere not only facilitates the charge transfer, but also modulates the electronic structure, which are beneficial to intrinsic bifunctional activity. As a result, this Ag@CoCO3 catalyst yields a substantially enhanced bifunctionality compared to the pristine CoCO3 catalyst. Moreover, the homemade Ag@CoCO3 based ZABs provides a high peak power density of 146 mW cm−2, superior to 107 mW cm−2 for CoCO3 based ZABs and 111 mW cm−2 for commercial Pt/C-IrO2 based ZABs.

Rational coupling of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts is extremely important for practical overall water splitting, but it is still challenging to construct such bifunctional heterostructures. Herein, we present a metal–organic framework (MOF)-etching strategy to design free-standing and hierarchical hollow CoS2–MoS2 heteronanosheet arrays for both HER and OER. Resulting from the controllable etching of MOF by MoO42− and in-situ sulfuration, the obtained CoS2–MoS2 possesses abundant heterointerfaces with modulated local charge distribution, which promote water dissociation and rapid electrocatalytic kinetics. Moreover, the two-dimensional hollow array architecture can not only afford rich surface-active sites, but also facilitate the penetration of electrolytes and the release of evolved H2/O2 bubbles. Consequently, the engineered CoS2–MoS2 heterostructure exhibits small overpotentials of 82 mV for HER and 266 mV for OER at 10 mA cm−2. The corresponding alkaline electrolyzer affords a cell voltage of 1.56 V at 10 mA cm−2 to boost overall water splitting, along with robust durability over 24 h, even surpassing the benchmark electrode couple composed of IrO2 and Pt/C. The present work may provide valuable insights for developing MOF-derived heterogeneous electrocatalysts with tailored interface/surface structure for widespread application in catalysis and other energy-related areas.

Sodium-ion hybrid capacitors (SIHCs) show great promise due to their combination of high energy-storage properties and low cost of Na resources. Yet most anodes in SIHCs suffer from sluggish Na+-diffusion kinetics and relatively low specific capacity, which restrict their widespread development. Herein, bowl-like VS2 nanosheet arrays are uniformly and robustly anchored on a carbon nanofiber (CNF) substrate through a one-step solvothermal method. The bowl-like VS2 is featured with an ultrathin thickness (several atomic layers), intrinsically metallic conductivity and an interconnected array architecture. This unique structural design can not only facilitate ultrafast Na+ ion-diffusion, but also suppress capacity decay of VS2 that is caused by the conversion process below 0.3 ​V. DFT calculations demonstrate a faster Na+ transport rate and a lower diffusion energy barrier for the VS2/C interface than for the VS2/VS2 bilayer. The quasi-solid-state SIHC full cell that integrates the CNF@VS2 anode and the graphene sheets-wrapped carbon nanofiber (CNF@GS) cathode, displays prominent energy//power densities in the voltage range of 0.0–4.0 ​V (116 ​Wh kg−1 ​at 0.4 ​kW ​kg−1; 66 ​Wh kg−1 ​at 40 ​kW ​kg−1 based on the total mass of both electrodes), outperforming recent SIHCs.

Metal-ion hybrid capacitors are regarded as promising power sources for portable electronics because of numerous opportunities in designing the anode/cathode couple to realize high performance and device flexibility. Here we demonstrate our rational design of a porous-fiber network based electrode for quasi-solid-state flexible Na-ion hybrid capacitors. A SiO2-etching approach is deployed to synthesize the freestanding porous carbon nanofiber (PCNF) membrane that is both mechanically robust and light (~1 mg cm−2). The PCNF serves as a 3D scaffold for the uniform growth of MoS2@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanosheets. The resultant PCNF@MoS2@PEDOT double core/shell nanofiber electrode not only maintains the intrinsic high-capacity of MoS2 for Na-ion storage, but also renders long-term cyclability and high rate performance. The constructed quasi-solid-state Na-ion hybrid capacitors can tolerate arbitrary bending and folding, and has a much lower self-discharge rate (15 mV h-1) compared to symmetric capacitors. Accepted version

Layered lithium cobalt oxide, LiCoO2 (LCO), is a promising catalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR); however, its bifunctional activity is still far from desirable. Here, a novel heterointerface of Co@LCO nanofibers (Co@LCO-NFs) is developed via an elegant in situ exsolution approach to promote bifunctionality. This in situ exsolution promises improved electrical conductivity, rich oxygen vacancies, and in particular a modulated electronic structure, thereby demonstrating a substantially enhanced bifunctional activity. Density functional theory calculations further reveal that the synergistic coupling of LCO and Co results in strengthened covalency of Co–O and facilitated OER/ORR kinetics. As a result, an assembled Zn–air battery using the Co@LCO-NFs electrode delivers high peak power density with competitive cycling stability, favorably outperforming the benchmark Pt/C–IrO2 based batteries. This protocol provides new insights into designing heterostructured bifunctional catalysts for related energy conversion and storage devices.

The downwash airflow field of UAVs is insufficient under the dual influence of greenhouse structure and crop occlusion, and the distribution characteristics of the flight flow field of UAVs in greenhouses are unclear. In order to promote the application of UAVs in greenhouses, the flow field characteristics of UAVs in a greenhouse were studied herein. In a greenhouse containing tomato plants, a porous media model was used to simulate the obstacle effect of crops on the airflow. The multi-reference system model method was selected to solve the flow field of the UAV. Studies have shown that the airflow field generated by UAV flight in a greenhouse is mainly affected by the greenhouse structure. With the increase in UAV flight height, the ground effect of the downwash flow field weakened, and the flow field spread downward and around. The area affected by the flow field of the crops became larger, while the development of the crop convection field was less affected. The simulation was verified by experiments, and linear regression analysis was carried out between the experimental value and the simulation value. The experimental results were found to be in good agreement with the simulation results.

As a hybrid battery-supercapacitor energy-storage device, Na-ion capacitors (NICs) are regarded to show both high-energy performance and low lost. However, the sluggish electrochemical kinetics and low specific capacities of most reported anode materials, severely restrict their practical applications. Herein, we report that ultrafine Mo2C nanoparticles are homogeneously embedded within an N-doped carbon matrix (Mo2C@NC) through a simple solid-phase reaction. After sulfuration, the optimal MoS2@NC electrode exhibits a high discharge capacity (535.3 mAh g−1 at 0.1 A g−1) and outstanding rate capability (420.2 mAh g−1 at 20 A g−1 with a remarkable retention of 78% relative to 0.1 A g−1), but its cycle life is not satisfied. To address this issue, amorphous TiO2 coating of different thicknesses is further coated on MoS2@NC by atomic layer deposition. It is found that the electrode made of TiO2-coated MoS2@NC shows excellent cyclability with 100% capacity retention after 500 cycles at 2 A g−1. Furthermore, a novel hybrid NIC is constructed by using TiO2/MoS2@NC as an anode and commercial activated carbon (AC) as a cathode, delivering high energy and power densities (148 Wh kg−1/200 W kg−1, 64.4 Wh kg−1/20,000 W kg−1). The performance outperforms the recently reported NIC counterparts.

Transition-metal selenides are emerging as alternative bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR); however, their activity and stability are still less than desirable. Herein, ultrafine Co0.85 Se nanoparticles encapsulated into carbon nanofibers (CNFs), Co0.85 Se@CNFs, is reported as an integrated bifunctional catalyst for OER and ORR. This catalyst exhibits a low OER potential of 1.58 V vs. reversible hydrogen electrode (RHE) (EJ=10, OER ) to achieve a current density (J) of 10 mA cm-2 and a high ORR potential of 0.84 V vs. RHE (EJ=-1, ORR ) to reach -1 mA cm-2 . Thus, the potential between EJ=10, OER and EJ=-1, ORR is only 0.74 V, indicating considerable bifunctional activity. The excellent bifunctionality can be attributed to high electronic conduction, abundant electrochemically active sites, and the synergistic effect of Co0.85 Se and CNFs. Furthermore, this Co0.85 Se@CNFs catalyst displays good cycling stability for both OER and ORR. This study paves a new way for the rational design of hybrid catalysts composed of transition-metal selenides and carbon materials for efficiently catalyzing OER and ORR.

Cr-modified ZSM-5 molecular sieve catalysts were prepared by the methods of hydrothermal technique [Cr-ZSM-5(H)], ion-exchange [Cr-ZSM-5(E)] and impregnation [Cr-ZSM-5(I)], the catalytic performance of the prepared catalysts in the process of isoamyl alcohol to isovaleric acid was investigated, and their physicochemical properties were characterized by XRD, FT-IR, BET, SEM and TG. The results showed that the catalyst Cr-ZSM-5(H) exhibited higher activity with isoamyl alcohol conversion of 44.97%, isovaleric acid selectivity of 78.78% and isovaleric acid yield of 35.43%, superior to Cr-ZSM-5(E) and Cr-ZSM-5(I), because of its suitable pore diameter, slower deposition rate, and more Cr-incorporation.

TiO2 is recognized as a promising anode material for sodium-ion batteries (SIBs) due to its low-cost and high structural stability, but it suffers from intrinsically poor electrical conductivity and low electrochemical activity at high rates. Herein, an in-situ Fe-doping strategy is designed to increase sodium-ion storage performance of TiO2/carbon nanofibers by a simple electrospinning method. The combination of Fe-doping with one-dimensional carbon structure could enable fast electron and Na+ ion transport of TiO2. As a result, the Fe-TiO2/carbon nanofiber electrode exhibits high specific capacity (283 mAh g−1 at 0.5 C), excellent rate capability (140 mAh g−1 at 30 C) and long cycling stability (98% retention after 3000 cycles), which is obviously superior to pure TiO2/carbon nanofiber and other TiO2-based anodes reported in the literatures. These results indicates the powerful effect of in-situ Fe-doping for enhancing the Na-storage property of TiO2.

Development of cost-effective, highly-active and durable catalysts for oxygen evolution reaction (OER) is critical to sustainable energy conversion and storage devices. Perovskite oxides are exploited as a research frontier on OER, however, their activity and stability are still far from desirable. Herein, we highlight a paradigm shift in the design of highly efficient perovskite-type catalysts for OER by engineering anion defect. The Cl-doped LaFeO2.85Cl0.15 perovskite demonstrates an enhanced OER activity, which is attributed to the abundant surface oxygen vacancies and low adsorption energy of H2O molecule after Cl doping. Moreover, the LaFeO2.85Cl0.15 catalyst also delivers an improved electrocatalytic durability, in contrast to the pristine LaFeO3 catalyst.

Implementing sustainable energy conversion and storage technologies is highly reliant on crucial oxygen electrocatalysis, such as the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). However, the pursuit of low cost, energetic efficient and robust bifunctional catalysts for OER and ORR remains a great challenge. Herein, the novel Na-ion-deficient Na2-x CoP2 O7 catalysts are proposed to efficiently electrocatalyze OER and ORR in alkaline solution. The engineering of Na-ion deficiency can tune the electronic structure of Co, and thus tailor the intrinsically electrocatalytic performance. Among the sodium cobalt phosphate catalysts, the Na1.95 CoP2 O7 (NCPO5) catalyst exhibits the lowest ΔE (EJ10,OER -EJ-1,ORR ) of only 0.86 V, which favorably outperforms most of the reported non-noble metal catalysts. Moreover, the Na-ion deficiency can stabilize the phase structure and morphology of NCPO5 during the OER and ORR processes. This study highlights the Na-ion deficient Na2-x CoP2 O7 as a promising class of low-cost, highly active and robust bifunctional catalysts for OER and ORR.

Lithium-ion capacitors (LICs) are considered to be promising power sources due to their combination of high-rate capacitors and high-capacity batteries. However, development of a high-performance L...

Designing and optimizing visible-light-driven photocatalyst with cost-efficiency and high performance is very imperative and highly challenging for photocatalytic hydrogen evolution reaction. Herein, g-C3N4/Mo2C hybrid photocatalyst with one dimensional (1D) heterostructure for highly enhanced photocatalytic H2 generation activity were obtained by a facile two step processing, in which Mo2C nanoparticles were highly dispersed on rod-like g-C3N4 surface. Attributed to the synergistic effect of 1D structure and Mo2C co-catalyst, the resultant g-C3N4/Mo2C sample exhibits an impressive visible-light photocatalytic H2 production rate of up to 507 μmol·h−1·g−1 and quantum efficiencies of 3.74% at 420 nm, which is 9.8 times higher than that of bulk g-C3N4, indicating that decorating Mo2C as co-catalysts on the surface of g-C3N4 leads to the improved visible light absorption, promoted charge separation and enhanced the following H2-evolution rate. Moreover, the mechanism for the photocatalytic activity enhancement was also discussed. This study provides a guide for researchers to design efficient g-C3N4-based hybrid photocatalysts with excellent stability and photocatalytic activity during the photoreaction process.

Developing novel methods to prepare hollow one-dimensional (1D) carbon nitride (g-C3N4) nanostructure is highly attractive in photocatalytic water splitting for hydrogen production. Herein, a simple, self-assembly synthesis of coral-like 3D porous P-doped g-C3N4 tubes (PCNT) by the combination of pyrolysis and freeze-drying method was reported. Attributed to the integrated merits of 1D tubular structure, 2D nanosheets and phosphorus doping, the as-prepared hollow PCNT exhibits superior photocatalytic activity under visible light irradiation. Owing to their higher specific surface area, enhanced light absorption, and better charge carrier separation and transfer, the maximum apparent photocatalytic hydrogen evolution rate of PCNT is 2020 μmol g−1 h−1, which is about 4.7 folds and 22.4 folds than that of g-C3N4 tubes and pristine bulk g-C3N4, respectively. Moreover, a possible photocatalytic mechanism and nanostructure formation process based on the experimental results are proposed. The novel growth strategy developed here may offer a new avenue for the rational design and synthesis of potentially efficient photocatalyst with 1D/2D integrated nanoarchitecture.

TiO2 has been a promising anode material for sodium-ion batteries because it is low-cost and environment-friendly. However, its electrochemical performance at high rates is still not acceptable. Herein, we synthesized a TiO2/C nanofiber material by the electrospinning method, and introduced air plasma treatments to modify the obtained material. Characterization results indicate that after the plasma treatments, the C fibers may have reacted with the plasma, and the surface areas of the nanofibers are increased. Electrochemical tests show this plasma treatment may be beneficial to the rate performance. The TiO2/C nanofiber with plasma treatment could deliver a high redox capacity of 191 mA h g−1 after 500 cycles at a very high rate of 10C (3300 mA g−1). The superior effects of the plasma treatment on the rate performance may provide new insights for developing better materials for practical sodium-ion batteries.

Developing advanced lithium-ion hybrid capacitors (LIHCs) has a critical challenge of matching kinetics and capacity between the battery-type anode and the capacitive cathode. In this work, a novel “dual carbon” LIHC configuration is constructed to overcome such a discrepancy. Specifically, hollow nitrogen-doped carbon nanoboxes (HNCNBs) are synthesized by a simple template-assisted strategy. As an anode material (0.01–3 V vs. Li/Li+), the HNCNB electrode exhibits high specific capacity (850 mA h g−1 at 0.1 A g−1) and superior rate capability (321 mA h g−1 at 20 A g−1). After alkaline activation, the HNCNBs become highly porous (PHNCNBs), which offers better capacitance performance within the potential window from 2.5 to 4.5 V (vs. Li/Li+) than commercial activated carbon (AC). Coupling a pre-lithiated HNCNB anode with a PHNCNB cathode forms a dual-carbon LIHC. Since the similar hollow structure in both electrodes could diminish the diffusion distance, the as-prepared HNCNB//PHNCNB LIHC provides high energy densities of 148.5 and 112.1 W h kg−1 at power densities of 250 and 25 000 W kg−1, respectively, together with long-term cycling stability, which efficiently bridges the gap between supercapacitors and lithium ion batteries. Furthermore, the self-discharge behavior and the temperature-dependent performance are also investigated.

Electrochemical oxygen evolution reaction is an appealing way to alleviate energy and environmental crisis. Perovskite oxides are supposed as attractive low-cost alternative electrocatalysts for oxygen evolution reaction relative to the IrO2 and RuO2 electrocatalysts. In this study, Fe-Ni coupled perovskite oxides, Pr0.5Ba0.5Fe1-xNixO3-δ, are proposed as novel electrocatalysts for oxygen evolution reaction in alkaline solution. The electrocatalytic activity of perovskites are optimized by engineering the couple of Fe-Ni cations. We identify a possible correlation between the enhancement in the activity and the amount of surface oxygen vacancies, OH− adsorption, charge transfer kinetics as well as eg-filling. The Pr0.5Ba0.5Fe0.975Ni0.025O3-δ electrocatalyst demonstrates excellent activity for oxygen evolution reaction, favorably compared to other the state-of-the-art perovskite electrocatalysts. The encouraging results indicate that Pr0.5Ba0.5Fe1-xNixO3-δ series is a promising class of electrocatalysts for practical application of oxygen evolution reaction.

Hollow micro-/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a "top-down" casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic-layer-deposition (ALD) Al2 O3 layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)-carbon composite hollow fibers after removal of Al2 O3 . Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni-based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as-obtained hollow V2 O3 -C fiber membrane is employed as a freestanding and flexible electrode for lithium-ion capacitor. The device shows an impressive energy density and a high power density. Accepted version This research is supported by National Natural Science Foundation of China (NSFC) Grants (51702295). Support from the Sino-Singapore International Joint Research Institute (JRI, Project Number: 204-A018002) is also appreciated.

Rational design of highly active, economical and stable electrocatalysts for hydrogen evolution reaction (HER) is still a great challenge for future applications. Herein, we use a 2D metal-organic framework array as the reactive template and precursor, to fabricate a hybrid nanosheet array of nitrogen-rich CoS2@nitrogen-doped carbon on Ti foil substrate (N–CoS2@NC/Ti) through a simple thermal treatment in the presence of thiourea. Owing to the prominent synergistic effect of the coupling between CoS2 and NC, a high content of Co-Nx species as well as unique nanoarray architectures, the as-synthesized N–CoS2@NC/Ti electrode exhibits remarkable activity and robust durability for HER under both acidic and alkaline conditions, which is obviously superior to the CoS2@NC/Ti .

Sodium-ion batteries have been widely considered as promising energy storage systems due to the abundance and low cost of sodium. However, to find a kind of anode material with appropriate sodium storage and high structural stability still remains challenging. In this work, self-supported porous carbon fibers were prepared by electrospinning technique and plasma treatments. It's found that the porous carbon fibers become more loose after the plasma treatments, and the surface compositions are changed. Results show that the material after plasma treatments could deliver capacities higher than 200 mAh/g when the current density is 1000 mA/g. EIS results show that the charge transfer resistances of the treated material keep more stable after electrochemical cycles. And these improvements may be results of the plasma treatments. Detailed mechanisms are studied in this research.

The development of an efficient, robust, and low-cost catalyst for water electrolysis is critically important for renewable energy conversion. Herein, we achieve a significant improvement in electrocatalytic activity for both the oxygen-evolution reaction (OER) and the hydrogen-evolution reaction (HER) by constructing a novel hierarchical PrBa0.5Sr0.5Co2O5+δ (PBSC)@FeOOH catalyst. The optimized PBSC@FeOOH-20 catalyst consisted of layered perovskite PBSC nanorods and 20 nm thick amorphous FeOOH nanoflakes exhibiting an excellent electrocatalytic activity for the OER and the HER in 0.1 M KOH media, delivering a current density of 10 mA cm-2 at overpotentials of 390 mV for the OER and 280 mV for the HER, respectively. The substantially enhanced performance is probably attributed to the hierarchical nanostructure, the good charge-transfer capability, and the strong electronic interactions of FeOOH and PBSC. Importantly, an alkaline electrolyzer-integrated PBSC@FeOOH-20 catalyst as both the anode and cathode shows a highly active overall water splitting with a low voltage of 1.638 V at 10 mA cm-2 and high stability during continuous operation. This study provides new insights into exploring efficient bifunctional catalysts for overall water splitting, and it suggests that the rational design of the oxyhydroxide/perovskite heterostructure shows great potential as a promising type of electrocatalysts.

Electroreduction of CO2 into liquid fuels is an appealing strategy to alleviate energy and environmental crisis. However, the poor product selectivity and insufficient energetic efficiency of current catalysts for CO2 electroreduction severely hinder their widespread applications. Herein, a partially reduced Sn/SnO2 porous hollow fiber (PHF) is, for the first time, proposed to electroreduce CO2 into formate with high selectivity, efficiency and durability. The Sn/SnO2 PHF is synthesized via a facile combination of electrospinning and reduction process. The partial reduction can efficiently tune the electronic structure of Sn and create abundant oxygen vacancies, and consequently tailors the electrocatalytic ability. Importantly, Sn/SnO2 PHF demonstrates a high formate faradaic efficiency of 82.1% and a considerable formate partial current density of ∼22.9 mA cm−2, favorably rivals most state-of-the-art catalysts for electroduction CO2 into formate. This study provides new insights into exploring efficient catalysts for CO2 electroreduction, and it suggests that the rational design of metal/metal oxide heterostructure shows great potential as a promising type of electrocatalysts.

Developing highly active and low-cost electrocatalysts with superior durability is attractive but challenging for energy-saving electrolytic hydrogen generation via water electrolysis. Herein, a novel metal-organic framework (MOF)-based growth-etching-phosphorization strategy is reported to construct hierarchical porous CoP nanostructure arrays on nickel foam substrate (HP-CoP NA/NF) for overall water splitting (OWP). Interconnected 2D cobalt-based MOF are fabricated via an aqueous solution reaction at room temperature, and then solid MOFs are uniformly converted into porous CoP arrays with hierarchical 3D configuration through a Co2+−etching process with subsequent phosphorization treatment. This unique array architecture is beneficial for providing highly exposed active sites, shortening ion diffusion path and promoting gas release during the electrochemical reactions. Resultantly, this MOFs-derived CoP catalyst exhibits an outstanding electrocatalytic activity in catalyzing not only hydrogen and oxygen evolution reactions with the low overpotentials of 70 and 258 mV at 10 mA cm−2, respectively, but also some other small molecules electro-oxidation reactions, especially for urea oxidation reaction. Furthermore, the two-electrode electrolyzer comprising bifunctional HP-CoP NA/NF electrode delivers a current density of 10 mA cm−2 at an ultralow cell voltage of 1.38 V in the presence of urea, which is 180 mV smaller than that of pure water splitting. This work introduces a reference for the development of MOF-derived hierarchical nanostructured catalysts for energy-saving water splitting.

The development of highly active dual-functional electrocatalysts, especially for oxygen evolution reaction (OER), is highly desirable to electrocatalyze water splitting for hydrogen production . Herein, a cobalt metal-organic frameworks (Co-MOFs) array is employed as the platform to fabricate oxygen-defect-rich Co 3O4 flakes that are vertical grown on nickel foam substrates. This MOFs-derived Co3O4 arrays show a hierarchical interconnected porous flake network structure with tunable oxygen vacancies. The unique structural features obtained from an optimal hydrogenation condition render outstanding catalytic performance toward the oxygen evolution in alkaline media (an ultralow overpotential of 205 mV at 10 mA cm−2; a small Tafel slope of 65.3 mV dec−1 as well as high stability). This OER performance is among the best non-noble metal catalysts reported to date. Meanwhile, this defect-rich Co3O4 array electrode is also efficient for catalyzing hydrogen evolution in the same basic solution (overpotential of ∼108 mV at 10 mA cm−2). The electrolyzer for overall water splitting can deliver a current density of 100 mA cm−2 at a cell voltage as low as 1.84 V. Density functional theory calculation reveals that the enhanced OER performance mainly arises from the oxygen vacancies and consequently the lowered activation energy as well as improved electrical conductivity.

Replacement of oxygen evolution (OER) by the more readily oxidized urea is considered to be a promising strategy for electrocatalytic water-splitting. In this work, we report a Fe O P film on nickel foam (Fe O P/NF) via atomic layer deposition (ALD) of iron oxide and a subsequent phosphonation process, which acts as a superior bifunctional electrocatalyst for both urea evolution reaction (UOR) and hydrogen evolution reaction (HER). Benefiting from the synergetic effects, the Fe O P/NF exhibits a low potential of 1.34 V (vs. RHE) at 10 mA cm−2 and a low Tafel slope of 57.2 mV dec−1 for UOR. Combined with the high HER activity of Fe O P/NF, the urea-based overall water splitting can be performed with an low voltage of 1.43 V to deliver 10 mA cm−2 in 1.0 M KOH with 0.5 M urea, which is 200 mV lower than that for pure water splitting.

Nano composite of Ruddlesden-Popper electrocatalyst-oxygen ionic conductor, (Pr0.9La0.1)2(Ni0.74Cu0.21Nb0.05)O4+δ (PLNCN)-Ce0.9Gd0.1O2−δ (GDC), is developed as composite cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs) via a infiltration way. The electrochemical behavior of PLNCN-GDC nanostructured electrode is assessed with respect to infiltration loading and oxygen partial pressure. The optimized PLNCN loading can improve charge transfer dynamics for electrochemical oxygen reduction reaction, thus promoting cathode performance. Importantly, the encouraging results of single cell highlight high activity and good CO2 tolerance of PLNCN-GDC nanostructured cathode.

Flexible energy storage devices have become critical components for next-generation portable electronics. In the present work, a flexible quasi-solid-state lithium-ion capacitor (LIC) is developed based on graphene-based bendable freestanding films in a gel polymer electrolyte. A graphene encapsulated Fe3O4 nanocube hybrid film (rGO@Fe3O4) has been fabricated as the anode of LICs through a filtration assisted self-assembly and the subsequent thermal annealing process. In this hybrid architecture, flexible and ultrathin graphene shells uniformly enwrap the Fe3O4 within the whole film, which can effectively suppress the aggregation of Fe3O4 and also accommodate the volume change of Fe3O4 during the cycling process. As a consequence, the electrochemical performance of the rGO@Fe3O4 half-cell versus Li/Li+ shows high specific capacity (731 mA h g−1 at 0.1 A g−1), excellent rate capability (210 mA h g−1 at 10 A g−1) and superior cycling stability (98% retention after 600 cycles). After chemically etching rGO@Fe3O4 with hydrochloric acid, a holey rGO film is successfully obtained as a high-rate cathode of LICs. On the basis of such a flexible anode and cathode, the as-fabricated quasi-solid-state LIC device delivers a high energy density of 148 W h kg−1, a high power density of 25 kW kg−1 (achieved at 70 W h kg−1) and an excellent capacity retention of 82% after 2000 cycles. More importantly, the rGO@Fe3O4//holey rGO LIC shows good mechanical flexibility with stable Li-storage capacities under harsh bending.

Conventional supercapacitors often suffer from low energy density. Hybrid Na-ion capacitors (NICs) are emerging as an important energy-storage device with high-energy and high-power output. They possess complementary merits of a high-capacity battery-type anode and a high-rate capacitive cathode. However, the existing anodes (e.g., carbon, TiO2, and Na2Ti2O5) are often limited by sluggish kinetics and low capacities of Na-ion storage. Here we report the fabrication of ultrathin MoS2 nanosheet arrays vertically anchored on bagasse-derived three-dimensional (3D) porous carbon frameworks (MoS2@BPC) as NIC anodes through a facile two-step solid-phase reaction strategy (BPC → Mo2C@BPC → MoS2@BPC). During the solid-phase synthesis process, the formation of Mo2C intermediates is the key to a successful growth of powder-type MoS2 nanosheet arrays on BPC. Meanwhile, the bagasse-derived porous cross-linked carbon structure can act as a 3D scaffold to effectively increase the conductivity, sodium-ion diffusion and structural stability of MoS2@BPC during charge–discharge processes. As a consequence, the MoS2@BPC electrode delivers a high specific capacity for Na-ion storage (490 mA h g−1 at 0.1 A g−1) with superior high-rate capability and cyclability (cycled over 5000 cycles at 2 A g−1). Coupled with BPC as the cathode, the hybrid electrode made of MoS2@BPC enables the NIC to deliver both high energy density (112.2 W h kg−1 at 55 W kg−1) and power density (8333 W kg−1 at 53.2 W h kg−1) as well as long cycling stability, which may bridge the supercapacitor–battery divide.

Fast−charging and high−capacity have become indispensable requirements for next−generation energy storage systems. However, large−scale fabrication of high−capacity anode materials for fast Li+ storage remains a huge challenge. Herein, natural hematite is employed as the starting material to achieve scalable synthesis of nitrogen−doped carbon nanotube−buffered FeSe2 (FeSe2@N−CNT) through a facile catalyzing & selenizing process. The readily−available raw materials and simple processing procedures are suitable to industrial−level batch production. In this FeSe2@N−CNT composite, the FeSe2 particles are efficiently encapsulated into the interwoven carbon nanotube network, which can enlarge the contact area with electrolyte, enhance the electrical conductivity, shorten the Li+/e– diffusion length and buffer the drastic volume variation of FeSe2 during lithiation/delithiation. As an anode material of lithium ion batteries (LIBs), the FeSe2@N−CNT electrode delivers a significantly high specific capacity of 806 mAh g−1 at a high current density of 20 A g−1 (relative to 915 mAh g−1 at 0.1 A g−1). More importantly, long−term cycle stability (953 mAh g−1 after 1500 cycles at 10 A g−1) is achieved, which outperforms most FeSe2−based Li+ storage anodes reported so far. The easy−to−implement mass production and the high Li+ storage property enable FeSe2@N−CNT as a promising candidate as a commercial anode for LIBs.

One of the technical hurdles to commercialization of intermediate temperature solid oxide fuel cells (IT-SOFCs) is the requirement of highly efficient cathode materials. Herein, we report the evaluation of Sr 2 Fe 1.5 Mo 0.5−x Sn x O 6−δ (x = 0, 0.1, 0.3 and 0.5, abbreviated as SFM, SFMS1, SFMS3, and SFS) oxides as cobalt-free cathode materials of IT-SOFCs. XPS analysis demonstrates the presence of variable valences among Fe, Mo and Sn elements, suggesting a small polaron hopping mechanism for electronic conduction. First principle calculations reveal that SFMS3 provides the lowest average formation energy of oxygen vacancy (E vac O*) among these perovskites. The relatively low area specific resistances are obtained with SFMS3 electrode based on La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3−δ electrolytes, indicating its high activity for oxygen reduction reaction. Power density of the single cell using SFMS3 cathode as high as 618 mW cm −2 at 800 °C is achieved, and operation lasts for 200 h without obvious degradation. The encouraging results promise SFMS3 as an alternative cathode material for IT-SOFCs.

During the application of protonic ceramic fuel cells (PCFCs), Co species derived from Co-containing cathodes readily diffuse into electrolyte layer. In this study, the influence of cobalt doping on the sintering and protonic conducting properties of BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) electrolytes is evaluated. The Co-doped BZCYYb oxides prepared by a sol-gel way exhibit the orthorhombic perovskite structure. A trade-off relation between the sinterability and protonic conductivity of Co doped BZCYYb oxides is identified. Furthermore, BaZr0.1Ce0.68Y0.1Yb0.1Co0.02O3−δ (BZCYYbC2) with a compromise between sinterability and protonic conductivity is further applied as electrolyte of a single cell. The single cell with BZCYYbC2 electrolyte demonstrates a competitive power density of 0.67 W cm−2 at 700 °C.

Layered perovskite oxides are well known to possess significant electronic, magnetic and electrochemical properties. Herein, we highlight a novel layered perovskite PrBaMn1.5Fe0.5O5+δ (PBMFO) as electrodes of symmetrical solid oxide fuel cells (SSOFCs). The layered PBMFO shows high electrical conductivity of 112.5 and 7.4 S cm−1 at 800 °C in air and 5% H2/Ar, respectively. The single cell with PBMFO symmetric electrodes achieves peak power density of 0.54 W cm−2 at 800 °C using humidified hydrogen as fuel. Moreover, PBMFO electrodes demonstrate good redox stability and high coking tolerance against hydrocarbon fuel.

A Ruddlesden–Popper oxide (Pr0.9La0.1)2(Ni0.74Cu0.21Nb0.05)O4+δ (PLNCN)-infiltrated BaZr0.1Ce0.7Y0.2O3-δ (BZCY) is developed as an electrode for protonic ceramic fuel cells (PCFCs). PLNCN nanoparticles are evenly dispersed on the surface of BZCY skeleton by using the infiltration technology. The electrochemical behavior of the PLNCN-infiltrated BZCY electrodes are evaluated in terms of infiltration loading and temperature. The impedance results of symmetric cells suggest that the optimized loading of PLNCN is approximately 46.1 wt%. Power density of the single cell as high as 0.77 W cm−2 is achieved at 700 °C by using the 43.6 wt% PLNCN-infiltrated BZCY cathode, and the cell could be operated without degradation at 600 °C for 200 h; this finding indicates a promising alternative cathode for PCFCs.

Cation disordered rock-salt lithium-excess oxides are promising candidate cathode materials for next-generation electric vehicles due to their extra high capacities. However, one major issue for these materials is the distinct decline of discharge capacities during charge/discharge cycles. In this study, Al2O3 layers were coated on cation disordered Li1.2Ti0.4Mn0.4O2 (LTMO) using atomic layer deposition (ALD) method to optimize its electrochemical performance. The discharge capacity after 15 cycles increased from 228.1 to 266.7 mAh g−1 for LTMO after coated with Al2O3 for 24 ALD cycles, and the corresponding capacity retention enhanced from 79.7 to 90.9%. The improved cycling stability of the coated sample was ascribed to the alleviation of oxygen release and the inhibition on the undesirable side reactions. Our work has provided a new possible solution to address some of the capacity fading issues related to the cation disordered rock-salt cathode materials.

Oxygen electrocatalysis is an efficient and environmentally friendly electrochemical approach serving for various sustainable energy storage and conversion devices. Rational design of integrated electrocatalysts is emerging as a promising and challenging strategy to drive oxygen evolution and reduction reactions (OER and ORR). Herein, CoNi alloy nanoparticles exsolved on LiFe0.8Co0.1Ni0.1O2 (LFCN) parent with strong coupling is proposed as a bifunctional electrocatalyst for OER and ORR. Thanks to the synergetic interplay of exsolved CoNi and LFCN parent as well as the increased surface oxygen defects, such CoNi-LFCN electrocatalyst demonstrates high bifunctional activity and good durability to catalyze OER and ORR in alkaline media. This protocol discloses an in-situ exsolution strategy to design hybrid electrocatalysts for OER, ORR, and other electrocatalytic reactions.

CoP is demonstrated to be efficient for hydrogen evolution reaction (HER), but it suffers from unfavorable electronic and geometric structures to meet the requirement for future hydrogen economy. In this work, hierarchically porous N-doped carbon incorporated Mo-doped CoP nanosheet arrays are homogeneously grown on titanium foils (denoted as Mo-CoP/NC/TF) using a metal–organic-framework (MOF)-etching strategy. DFT simulations manifest that Mo dopants and N-doped carbon incorporation can synergistically modify the electronic structure of CoP, bringing optimal hydrogen adsorption free energies and accelerated interfacial charge transfer. Moreover, hierarchical nanoarray architectures can generate abundant accessible active sites, facile ion-diffusion path, and open-channels for gas release. Benefiting from these electronic and geometric advantages, the Mo-CoP/NC/TF electrocatalysts display superior activity and outstanding stability for pH-universal HER, requiring overpotentials of 59, 130, and 78 mV to drive a current density of 10 mA cm−2 in acidic, neutral, and alkaline electrolytes, respectively, which rivals most of the state-of-the-art non-precious electrocatalysts. This work may inspire the design and exploration of highly active and durable electrocatalysts by synergistically tailoring electronic and geometric structures toward hydrogen evolution.

Developing transition-metal based bifunctional electrocatalysts to efficiently drive oxygen evolution reaction and oxygen reduction reaction is an urgent demand for the implementation of rechargeable Zn-air batteries. Transition-metal sulfides are emerging as alternatives to precious metal-based electrocatalysts, however, their bifunctional activities are usually restricted by inferior electrical conductivities and limited electrochemical active sites. Herein, we highlight a novel metal-organic frameworks derived nitrogen-doped carbon nanofiber coupled FeS2–CoS2 (FeS2–CoS2/NCFs) by a combination of electrospinning and atomic-layer-deposition approach. Benefiting from the large exposed surface active sites of hierarchical structure and the abundant interfacial vacancies in FeS2–CoS2 heterointerface, the FeS2–CoS2/NCFs integrated electrocatalyst delivers a high bifunctional activity together with a good durability in alkaline medium. Notably, the liquid Zn-air battery assembled with this FeS2–CoS2/NCFs electrode displays a considerable peak power density of 257 mW cm−2, a high specific capacity of 814 mA h g−1 and a long cycling life of 250 h, superior to precious metal based Zn-air batteries. Moreover, the flexible solid-state Zn-air battery using such FeS2–CoS2/NCFs electrode can stably power LED panels even under twisting state, demonstrating practical potentials in wearable and portable electrochemical devices.

The Cr deposition and poisoning on electrolyte of solid oxide fuel cells (SOFCs) is critical because the electrolyte at cathode side is exposed to gaseous Cr species. A comparison of Cr deposition and poisoning on La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) and Gd0.1Ce0.9O2−δ (GDC) electrolytes is studied, in order to reveal the compatibility of SOFCs. The XPS results show that the little Cr deposition on GDC surface at 800 °C is likely caused by physical deposition. In the case of LSGM surface, Cr deposition is also physical deposition process at 600 °C and 700 °C, while both physical and chemical deposition processes at 800 °C. Moreover, the obviously reduced electrical conductivity by Cr poisoning is obtained on LSGM rather than GDC. The results indicate that the GDC electrolyte promises higher Cr tolerance than LSGM electrolyte.

Sm0.5Sr0.5CoO3−δ (SSC) infiltrated Ce0.9Gd0.1O2−δ (GDC) composite cathodes are developed for protonic ceramic fuel cells (PCFCs). Although the SSC infiltrated GDC cathodes make little contribute to expending the reaction sites of water formation, it can significantly improve the oxygen reduction dynamics among the whole electrochemical reaction. The symmetric half cell and single cell testing results demonstrate the high electrochemical activity of SSC infiltrated GDC cathodes. Moreover, the single cell is stable at 600 °C for 120 h in humidified H2 and humidified H2 CO. The encouraging results indicate that the SSC infiltrated GDC could be the promising composite cathodes for application in PCFCs.

The effect of bismuth oxide addition on the sintering behavior and electrical properties of BaZr0.3Ce0.5Y0.2O3−δ (BZCY) as an electrolyte for proton conducting solid oxide fuel cells (H-SOFCs) is studied. The introduction of Bi2O3 is beneficial to improving sinterability of BZCY, resulting in high density. Meanwhile, the conductivity test indicates that BaZr0.3Ce0.5Y0.2O3-δ – 2 mol% Bi2O3 (BZCY-2) promises the highest conductivities. Further, single cells with BZCY-2 as the electrolyte are fabricated and evaluated. The cell with BZCY-2 presents excellent power densities, which reaches 0.67, 0.44, and 0.27 mW cm−2 at 700, 650, and 600 °C, respectively. The conductivities of BZCY-2 film are higher than BZCY in this work and other reported BZCY films. The encouraging results suggest that the addition of a small amount (2 mol%) of Bi2O3 to BZCY can significantly promote sinterability and electrical conductivity for H-SOFCs.

We report our findings on Ce0.9Gd0.1O2−δ (GDC) modified (Pr0.9La0.1)2(Ni0.74Cu0.21Nb0.05)O4+δ (PLNCN) ultrathin membranes as highly efficient and CO2-stable oxygen transporting membranes (OTMs). Until now, such membranes have offered the highest oxygen permeability among those CO2-stable membranes reported in the literature.

Rechargeable alkali metal-Se batteries have attracted a lot of attention due to their high capacity and low cost. However, the shuttle effect and volume change during charge/discharge are the main obstacles for further development of high-performance alkali-Se rechargeable batteries. In order to solve these issues, herein a biomass-derived 3D interconnected foam-like N-doped porous carbon (FNDPC) is synthesized as a Se-container for metal-Se batteries. In this FNDPC@Se structure, stable porous carbon hosts can serve as chambers for Se reacting with Li+, Na+ or K+. As expected, the FNDPC@Se electrode exhibits an ultrahigh rate performance and excellent cycling stability during the reversible storage of alkali metal ions. For Na-Se batteries, the high specific capacity of 354.9 mAh g−1 is achieved even at a high current density of 20 A g−1 and there is 90.7% capacity retention after 500 cycles at 2.0 A g−1. For Li-Se batteries, FNDPC@Se can offer an impressive rate capability with specific capacities of 653.1 mAh g−1 at 0.1 A g−1 and 350.4 mAh g−1 at 20 A g−1. In contrast, the performance of FNDPC@Se in K-Se batteries is relatively lower than that in Li-Se and Na-Se batteries. Moreover, different energy-storage mechanisms for three types of ions are also revealed by cycling voltammetry (CV). Therefore, FNDPC is considered to be a promising carbon host for alkali-Se batteries, and our reported method provides possibilities for mass production of alkali-Se battery through the cheap raw materials.

Rational design of bifunctional catalysts towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is vital for reversible Zn-air batteries. Here, we highlight the surface functionalized perovskite, oxygen vacancies-rich Ce0.9Gd0.1O2-δ (GDC) decorated Pr0.5Ba0.5CoO3-δ (PBC), as a novel bifunctional electrode for Zn-air batteries. Surface decoration by GDC can not only introduce the abundant electrochemically active oxygen vacancies for ORR and OER, but also improve the structure stability of perovskite against practical operation. Density functional theory calculations further reveal that O2 and H2O molecules readily adsorb on GDC surface rather than PBC surface. The resulting 20 wt.% GDC decorated PBC catalyst delivers a significantly higher bifunctionality than the pristine PBC. As a proof-of-concept, an assembled Zn–air battery using 20 wt.% GDC decorated PBC electrode demonstrates a considerable peak power density and a long cycling life. This study offers a facile and effective approach to design air electrode of rechargeable Zn-air batteries.

The development of economical and versatile catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is an exceedingly challenge for hydrogen production from water electrolysis. Herein, three-dimensional (3D) phosphorus-anion-decorated cobalt disulfide hollow nanosheet arrays are uniformly deposited on carbon cloth (P-CoS2 HNA/CC) through a MOF-based growth-sulfidation-phosphorization approach. Benefiting from the moderated electronic structure, maximum exposure of active surface sites and the unique 3D hollow conductive architecture, the optimal P-CoS2 HNA/CC delivers superior electrocatalytic activity with extremely low overpotentials of 250 and 80 mV to achieve a current density of 10 mA cm−2 for OER and HER in alkaline conditions, respectively. The corresponding two-electrode electrolyzer for overall water splitting requires a cell voltage of 1.56 V to attain a current density of 10 mA cm−2, close to commercial IrO2/CC || Pt/C/CC couple (1.55 V). Density functional theory (DFT) calculations demonstrate that decoration of P-anions into CoS2 electrocatalysts not only significantly tunes adsorption energetics of H- and O-containing intermediates, but also offers additional active sites for OER/HER process, dramatically boosting the catalytic activity of P-CoS2 HNA/CC. This work may shed some new light on the design of advanced and high-active electrocatalysts for overall water splitting.

Electrochemical reduction of CO2 (ECR) into formate is an efficient and environmentally friendly approach contributing to carbon-neutral cycle. However, conventional catalysts for ECR usually suffer from low product selectivity, inferior activity and poor durability. Herein, we highlight Bi nanoparticles embedded in nitrogen doped porous carbon (Bi@NPC) as a promising integrated catalyst for ECR. This catalyst demonstrates a remarkable formate faradaic efficiency of 92.0%, and more encouragingly, a high formate current density of 14.4 mA cm−2 at a low potential of −1.5 V (vs SCE) in 0.1 M KHCO3 solution, which is significantly superior to the individual Bi nanoparticles (Bi-NP). Besides, the Bi@NPC catalyst exhibits a robust durability for 20 h operation. The advanced electrocatalytic performance of the Bi@NPC catalyst is likely attributed to the ensemble effect of Bi nanoparticles and NPC matrix. This attractive route discloses a broad prospect for the development of a promising integrated catalyst for ECR.

Herein, self-assembly of hierarchical multihole g-C3N4 hexagon with excellent specific surface area (129 m2/g) and nitrogen vacancies were accomplished via a one-step polymerization of hydrothermal-treated dicyandiamide and ethylene-diamine-tetra-acetic acid (EDTA). The special chelate structure of EDTA efficiently enlarged a broad visible light response range, and the concentrations of EDTA promoted the self-assembly formation of different surface morphology. The photocatalytic H2 production rate under visible light for the optimal g-C3N4 hexagon (CN-20E) reaches 5839 μmol·g−1·h−1 and its apparent quantum efficiency reaches up to 7.3% at 420 nm, which has a 102 times higher for H2 production rate than that of bulk g-C3N4 (57 μmol·g−1·h−1). Special structure of the multihole hexagon endows them with remarkably visible light absorption, fast separation of photo-induced charge carriers, large surface areas as well as the exposure of potential photocatalytic active sites, thereby dramatically improved the H2 production property. Moreover, the forming process for the specific structure and the reaction mechanism of the enhanced photocatalytic activity were proposed according to the experimental results and theoretical calculations. This work exhibits a new avenue to rehandle graphitic carbon nitride precursor to build a grafted structure for developing highly efficient g-C3N4 in the practical photocatalytic application.

Oxygen electrocatalysis, including the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), is one of the most important electrochemical processes for sustainable energy conversion and storage technologies. Herein, nickel-based bicarbonates are, for the first time, developed as catalysts for oxygen electrocatalysis, and demonstrate superior electrocatalytic performance in alkaline media. Iron doping can significantly tune the real valence of nickel ions, and consequently tailor the electrocatalytic ability of bicarbonates. Among the nickel-based bicarbonates, Ni0.9 Fe0.1 (HCO3 )2 exhibits the highest bifunctional catalytic activity, with a potential difference of 0.86 V between the OER potential at a current density of 10 mA cm-2 and the ORR potential at a current density of -1 mA cm-2 , which outperforms most of the reported precious-metal-free catalysts. The present work provides new insights into exploring efficient catalysts for oxygen electrocatalysis, and it suggests that, in addition to the extensively studied transition metal hydroxides and oxides, bicarbonates and carbonates also show great potential as precious metal-free catalysts.

The pursuit of efficient and durable bifunctional electrocatalysts for oxygen reduction reaction and oxygen evolution reaction is urgently needed for the development of highly reversible lithium-oxygen batteries. Perovskite oxides are emerging as a novel research frontier to simultaneously catalyze oxygen reduction and evolution reactions, however, their activity and durability are still far from desirable. Herein, we propose a rational design of Ni3S2 decorated double perovskite PrBa0.5Sr0.5Co2O5+δ as an integrated electrocatalyst. A Ni3S2 layer with 10 nm thickness is uniformly anchored on electrospun PrBa0.5Sr0.5Co2O5+δ nanofibers via the atomic layer deposition technology and the following sulfudation process. Notably, the lithium-oxygen batteries employing the as-prepared catalyst shows the excellent performance with a narrow overpotential (0.68 V at 1000 mAh g−1), a high capacity (12874 mAh g−1 at 100 mA g−1) as well as the improved cycle stability (over 120 cycles) and rate capacity. The outstanding performance arises from the synergistic coupling of Ni3S2 and PrBa0.5Sr0.5Co2O5+δ as well as the hierarchical porous structure with sufficient catalytic active sites. This work provides an innovative method to combine the metal chalcogenides and perovskite oxides, and the results suggest that the integrated Ni3S2/PrBa0.5Sr0.5Co2O5+δ has a great potential as bifunctional electrocatalyst for the reversible lithium-oxygen batteries.

Cation disordered rock-salt Li-excess cathode materials can deliver high reversible capacities (>250 mAh g−1). However, their commercialization has come to a standstill because of practical drawbacks, such as voltage fading, voltage hysteresis, and poor rate capability. Therefore, it is urgent to probe the kinetic and transport properties of this kind of cathode materials. For this aim, Li1.25Nb0.25Mn0.5O2, a typical material with cation disordered rock-salt structure, is used as an object for the investigations of kinetic properties for the first time. Through a series of detailed electrochemical measurements, DLi values are calculated to be in the order of 10−13–10−10 cm2 s−1 based on the GITT results. It is also found that the minimum values of the electrochemical impedances are in the middle range during both charge and discharge processes. Our findings may provide useful information for the design and modification of this kind of cathode materials in lithium-ion batteries.