Co3O4/MnO2/Hierarchically Porous Carbon as Superior Bifunctional Electrodes for Liquid and All-Solid-State Rechargeable Zinc-Air Batteries

Tip and heterogeneous effects co-contribute to a boosted performance and stability in zinc air battery

The zinc-air battery (ZAB) performance and stability strongly depend on the structure of bifunctional electrocatalyst for oxygen reduction/evolution reaction (ORR/OER). In this work, we combine the tip and heterogeneous effects to construct cobalt/cobalt oxide heterostructure nanoarrays (Co/CoO-NAs). Due to the formed heterostructure, more oxygen vacancies are found for Co/CoO-NAs resulting in a 1.4-fold higher ORR intrinsic activity than commercial carbon supported platinum electrocatalyst (Pt/C) at 0.8 V versus reversible hydrogen electrode (vs. RHE). Moreover, a fast surface reconstruction is observed for Co/CoO-NAs during OER catalysis evidenced by in-situ electrochemical impedance spectroscopy and Raman tests. In addition, the tip effect efficiently lowers the mass transfer resistance triggering a low overpotential of 347 mV at 200 mA cm-2 for Co/CoO-NAs. The strong electronic interplay between cobalt (Co) and cobalt oxide (CoO) contributes to a stable battery performance during 1200 h galvanostatic charge-discharge test at 5 mA cm-2. This work offers a new avenue to construct high-performance and stable oxygen electrocatalyst for rechargeable ZAB.

Cobalt Oxide-Based Electrocatalysts with Bifunctionality for High-Performing Rechargeable Zinc-Air Batteries

In recent years, the rapid growth in renewable energy applications has created a significant demand for efficient energy storage solutions on a large scale. Among the various options, rechargeable zinc-air batteries (ZABs) have emerged as an appealing choice in green energy storage technology due to their higher energy density, sustainability, and cost-effectiveness. Regarding this fact, a spotlight is shaded on air electrode for constructing high-performance ZABs. Cobalt oxide-based electrocatalysts on the air electrode have gained significant attention due to their extraordinary features. Particularly, exploration and integration of bifunctional behavior for energy storage has remarkably promoted both ORR and OER to facilitate the overall performance of the battery. The plot of this review is forwarded towards in-depth analysis of the latest advancements in electrocatalysts that are based on cobalt oxide and possess bifunctional properties along with an introduction of the fundamental aspects of ZABs, Additionally, the topic entails an examination of the morphological variations and mechanistic details mentioning about the synthesis processes. Finally, a direction is provided for future research endeavors through addressing the challenges and prospects in the advancement of next-generation bifunctional electrocatalysts to empower high-performing ZABs with bifunctional cobalt oxide.

Investigation of Highly Active Carbon-, Cobalt-, and Noble Metal-Free MnO2/NiO/Ni-Based Bifunctional Air Electrodes for Metal-Air Batteries with an Alkaline Electrolyte

Compared to other battery technologies, metal-air batteries offer high specific capacities because the active material at the cathode side is supplied by ambient atmosphere. To secure and further extend this advantage, the development of highly active and stable bifunctional air electrodes is currently the main challenge that needs to be resolved. Herein, a highly active carbon-, cobalt-, and noble-metal-free MnO₂/NiO-based bifunctional air electrode is presented for metal-air batteries in alkaline electrolytes. Notably, while electrodes without MnO₂ reveal stable current densities over 100 cyclic voltammetry cycles, MnO₂ containing samples show a superior initial activity and an elevated open circuit potential. Along this line, the partial substitution of MnO₂ by NiO drastically increases the cycling stability of the electrode. X-ray diffractograms, scanning electron microscopy images, and energy-dispersive X-ray spectra are obtained before and after cycling to investigate structural changes of the hot-pressed electrodes. XRD results suggest that MnO₂ is dissolved or transformed into an amorphous phase during cycling. Furthermore, SEM micrographs show that the porous structure of a MnO₂ and NiO containing electrode is not maintained during cycling.

Flexible Solid-State Metal-Air Batteries: The Booming of Portable Energy Supplies

The rapid development of portable and wearable electronics has given rise to new challenges and provoked research in flexible, lightweight, and affordable energy storage devices. Flexible solid-state metal-air batteries (FSSMABs) are considered promising candidates, owing to their large energy density, mechanical flexibility, and durability. However, the practical applications of FSSMABs require further improvement to meet the demands of long-term stability, high power density, and large operating voltage. This Review presents a detailed discussion of innovative electrocatalysts for the air cathode, followed by a sequential overview of high-performance solid-state electrolytes and metal anodes, and a summary of the current challenges and future perspectives of FSSMABs to promote practical application and large-scale commercialization in the near future.

Enhancing pseudocapacitive properties of cobalt oxide hierarchical nanostructures via iron doping

Through co-precipitation and post-heat processing, nanostructured Fe-doped Co₃O₄ nanoparticles (NPs) were developed. Using the SEM, XRD, BET, FTIR, TGA/DTA, UV-Vis, and techniques were examined. The XRD analysis presented that Co₃O₄ and Co₃O₄ nanoparticles that had been doped with 0.25 M Fe formed single cubic phase Co₃O₄ NPs with average crystallite sizes of 19.37 nm and 14.09 nm, respectively. The as prepared NPs have porous architectures via SEM analyses. The BET surface areas of Co₃O₄ and 0.25 M Fe-doped Co₃O₄ NPs were 53.06 m²/g and 351.56 m²/g, respectively. Co₃O₄ NPs have a band gap energy of 2.96 eV and an extra sub-band gap energy of 1.95 eV. Fe-doped Co₃O₄ NPs were also found to have band gap energies between 2.54 and 1.46 eV. FTIR spectroscopy was used to determine whether M-O bonds (M = Co, Fe) were present. The doping impact of iron results in the doped Co₃O₄ samples having better thermal characteristics. The highest specific capacitance was achieved using 0.25 M Fe-doped Co₃O₄ NPs at 5 mV/s, which corresponding to 588.5 F/g via CV analysis. Additionally, 0.25 M Fe-doped Co₃O₄ NPs had energy and power densities of 9.17 W h/kg and 472.1 W/kg, correspondingly.

Hybrid Carbon Sphere Chain-MnO2 Nanorods as Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc-Air Batteries

It is now recognized that the development of self-supported and efficient bifunctional air cathodes via the direct growth of earth-abundant catalysts onto the surface of the conductive collector would be a cutting-edge strategy to reduce interfacial resistance, enhance the mechanical tenure, and reduce the final weight and cost of manufacturing of rechargeable Zn-air batteries (ZABs). This work reports an innovative self-supported precious metal-free electrode, comprising carbon sphere chains (CSCs) directly grown onto a carbon paper (CP) substrate, wherein the CSCs have a functionalized surface bearing carbon nanobud defects, oxygen functional groups, and high-density MnO₂ hierarchical nanorods (NRs), uniformly coating the surface of CSCs. Not only is the metal-free functionalized CSC catalyst functional for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) but its combination with MnO₂ NRs impressively enhances the ORR/OER activities. A homemade ZAB assembled with functionalized CSC/MnO₂ air cathode can successfully power a timer for a period of 17 days with no voltage loss, whereas two series-connected ZABs can light up 39 red light-emitting diode (LED) bulbs. The self-supported and earth-abundant-based CSC/MnO₂ materials open up an opportunity for lightweight and cost-effective ZABs and metal-air batteries in general.

Hollow CoS2 anchored on hierarchically porous carbon derived from Pien Tze Huang for high-performance supercapacitors

The development of electrode materials with a high specific capacitance, power density, and long-term stability is essential and remains a challenge for developing supercapacitors. Cobalt sulfides (CoS₂) are considered one of the most promising and widely studied electrode materials for supercapacitors. Herein, CoS₂ and hierarchical porous carbon derived from Pien Tze Huang waste are assembled into a cobalt sulfide/carbon (CoS₂/PZH) matrix composite using a one-step hydrothermal method to resolve the challenges of supercapacitors. The resulting CoS₂/PZH composite material exhibits a hierarchical porous structure with hollow CoS₂ embedded in a PZH framework. The uniform dispersion of the hierarchical porous structure CoS₂/PZH is achieved due to the PZH framework, while the uniform decoration of the porous PZH with the hollow CoS₂ prevents the PZH from stacking easily. Moreover, the excellent synergistic effect of the hierarchical porous and hollow structure of CoS₂/PZH can shorten the electron/ion diffusion channels, expose additional active sites, and provide stable structures for subsequent reactions. As a result, the CoS₂/PZH composite material displays a high initial specific capacity of 447.5 F g^-1 at 0.5 A g^-1, a high energy density of 22.38 W h kg^-1, and long-term cycling stability (a retention rate of 92.3% over 10 000 cycles at 5 A g^-1).

Ru-incorporated Co3O4 nanoparticles from self-sacrificial ZIF-67 template as efficient bifunctional electrocatalysts for rechargeable metal-air battery

Ru-incorporated Co₃O₄ nanoparticles have been synthesized from self-sacrificial ZIF-67 template and utilized as efficient electrocatalysts towards oxygen reduction and evolution reactions (ORR and OER). Amongst, Ru@Co₃O₄-1.0 exhibited the optimum electrocatalytic behavior with an ultra-low potential gap (0.84 V) between the OER potential (1.61 V at 10 mA cm^-2) and ORR half-wave potential (0.77 V). The zinc-air battery using Ru@Co₃O₄-1.0 as a cathode presented high specific capacity (788.1 mAh g^-1) and power density (101.2 mW cm^-2). Meanwhile, this battery possessed relatively lower voltage gap and higher cycling stability compared with the commercial Pt/C-based one. Ruthenium incorporation induced remarkable lattice expansion of Co₃O₄ and engineered more oxygen vacancies, promoting the lattice oxygen mobility from the subsurface/bulk phase onto surface. All these properties were recognized to be the crucial parameters for electrocatalytic activity improvement. This work provided a facile approach to design highly active metal oxide with broad potentiality for rechargeable metal-air batteries.

Advanced Zinc-Air Batteries with Free-Standing Hierarchical Nanostructures of the Air Cathode for Portable Applications

It is today advanced that the development of a free-standing (binderless) air cathode via direct growth of nonprecious metal electrocatalysts onto the surface of the conductive collector would be a cutting-edge strategy to reduce the interfacial resistance, improve the mechanical stability, and reduce the final weight and the cost of manufacturing. Here, for Zn-air batteries (ZABs), we propose an innovative binderless noble-metal-free hierarchical nanostructured bifunctional air cathode in which high-density MnO_x nanorods (NRs) are directly grown on carbon nanotubes (CNTs) themselves synthesized on a microfibrous carbon paper (CP) substrate. All carbon/MnO_x air cathodes achieved specific capacities very close to the theoretical value of 820 mAh g_Zn^-1. A very stable voltage gap between the charge and discharge processes along hundred cycles was obtained, demonstrating the stability and good bifunctional electrocatalytic activities of these cathodes toward the oxygen reduction reaction/oxygen evolution reaction in a real ZAB device. As a proof-of-concept for handheld electronic applications, a ZAB assembled with CP/MnO_x NRs as the air electrode and a Zn plate anode operated a timer for 14 days successfully, whereas two ZAB-based CNTs/MnO_x cathodes connected in series powered a 2 V light-emitting diode (LED) bulb and a 3 V multimeter. The proposed strategy and results may pave the way for the rational design of hierarchical free-standing bifunctional electrocatalysts for ZABs, other metal-air batteries, and fuel cells.

Atomically Dispersed Transition Metal-Nitrogen-Carbon Bifunctional Oxygen Electrocatalysts for Zinc-Air Batteries: Recent Advances and Future Perspectives

Rechargeable zinc-air batteries (ZABs) are currently receiving extensive attention because of their extremely high theoretical specific energy density, low manufacturing costs, and environmental friendliness. Exploring bifunctional catalysts with high activity and stability to overcome sluggish kinetics of oxygen reduction reaction and oxygen evolution reaction is critical for the development of rechargeable ZABs. Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts possessing prominent advantages of high metal atom utilization and electrocatalytic activity are promising candidates to promote oxygen electrocatalysis. In this work, general principles for designing atomically dispersed M-N-C are reviewed. Then, strategies aiming at enhancing the bifunctional catalytic activity and stability are presented. Finally, the challenges and perspectives of M-N-C bifunctional oxygen catalysts for ZABs are outlined. It is expected that this review will provide insights into the targeted optimization of atomically dispersed M-N-C catalysts in rechargeable ZABs.

Engineering Co3O4/MnO2 nanocomposite materials for oxygen reduction electrocatalysis

Stable and active electrocatalysts preparation for the oxygen reduction reaction (ORR) is essential for an energy storage and conversion materials (e.g. metal-air batteries). Herein, we prepared a highly-active MnO₂ and Co₃O₄/MnO₂ nanocomposite electrocatalysts using a facial co-precipitation approach. The electrocatalytic activity was examined in alkaline media with LSV and CV. Additionally, the physicochemical characteristics of the MnO₂ and Co₃O₄/MnO₂ composite materials were studied via SEM, XRD, BET, UV-Vis, TGA/DTA, ICP-OES and FTIR. Morphological studies indicated that a pure MnO₂ has a spherical flower-like architecture, whereas Co₃O₄/MnO₂ nanocomposites have an aggregated needle-like structure. Moreover, from the XRD investigation parameters such as the dislocation density, micro-strain, and crystallite size were analyzed. The calculated energy bandgaps for the MnO₂, Co₃O₄/MnO₂-1-5, and Co₃O₄/MnO₂-1-1 nanocomposites were 3.07, 2.6, and 2.3 eV, correspondingly. The FTIR spectroscopy was also employed to study the presence of M-O bonds (M = Mn, Co). The thermal gravimetric investigation showed that the Co₃O₄/MnO₂ nanocomposite materials exhibited improved thermal stability, confirming an enhanced catalytic activity of ORR for MnO₂/Co₃O₄-1-1 composite materials for ORR. These results confirm that the prepared Co₃O₄/MnO₂ composite materials are promising air electrode candidates for the energy storage and conversion technologies.

CoS2 /N-Doped Hollow Spheres as an Anode Material for High-Performance Sodium-Ion Batteries

In this work, we first synthesized polyacrylic acid (PAA) spheres and then used PAA as a template to load Co(OH)₂ particles onto its surface. The product of CoS₂ nanoparticles dispersed in N-doped hollow spheres (N-HCS) was prepared through sulfurization treatment (CoS₂ /S@N-HCS). During the sulfuration process, sulfur penetrates into the PAA, embedding into the graphite layer along with the carbonization process. It was found that during the charging and discharging process, the sulfur in the carbon layer will gradually dissolve out, thereby forming new ion diffusion channels in the carbon spheres and exposing more CoS₂ active sites. The CoS₂ /S@N-HCS composite exhibits a specific capacity of 729.6 mAh g^-1 after 500 cycles at a current density of 1 A g^-1 . The sodium-storage mechanism and reaction kinetics of the materials were further measured by in-situ electrochemical impedance spectroscopy, ex-situ X-ray diffraction, capacitance performance evaluation, and galvanostatic intermittent titration technique. The excellent cycling performance and rate capability demonstrated that the CoS₂ /S@N-HCS is a potential and prospective anode material for sodium-ion batteries.

Three-dimensional MOF-derived Co and N co-doped porous carbon bifunctional catalyst for the Zn–air battery

Considering their actual commercial large-scale applications, research on non-precious metal catalysts has garnered much interest.

Bimetallic Sulfide with Controllable Mg Substitution Anchored on CNTs as Hierarchical Bifunctional Catalyst toward Oxygen Catalytic Reactions for Rechargeable Zinc-Air Batteries

The exploitation of high-efficiency and cheap bifunctional cathode electrocatalyst is of significant importance to rechargeable zinc-air batteries. In this paper, a bimetallic sulfide coupled with a CNT ((Co, Mg)S₂@CNTs) hybrid catalyst is developed via a proposed vulcanization process. The (Co, Mg)S₂@CNTs) with controllable Mg substitution has a tailored crystal structure (amorphous and crystalline), which catalyzes the oxygen reduction/evolution reaction (ORR/OER). The active sites of CoS₂@CNTs are activated by doping Mg ions, which accelerates the kinetics of the oxygen adsorption for ORR and oxygen desorption for OER. Meanwhile, the hybrid catalyst exhibits a unique hierarchal morphology and a "catalytic buffer", which further accelerate the mass transfer of catalytic processes. In addition, the outer wall of CNTs as substrate effectively avoid the agglomeration of (Co, Mg)S₂ particles by reasonably providing adsorption sites. The inner and outer walls of CNTs form a high-speed conduction pathway, quickly transferring the electrons produced by oxygen catalytic reactions. As a result, the (Co, Mg)S₂@CNTs exhibit an ORR performance comparable with commercial catalyst Pt/C-RuO₂ and remarkable OER performance (E_j=10 = 1.59 V). The high power density of 268 mW cm^-2 and long-term charge/discharge stability of the zinc-air battery proves the feasibility of (Co, Mg)S₂@CNTs application in high-power devices.

Dual-Template Pore Engineering of Whey Powder-Derived Carbon as an Efficient Oxygen Reduction Reaction Electrocatalyst for Primary Zinc-Air Battery

Cost-effective and high-performance electrocatalysts for oxygen reduction reactions (ORR) are needed for many energy storage and conversion devices. Here, we demonstrate that whey powder, a major by-product in the dairy industry, can be used as a sustainable precursor to produce heteroatom doped carbon electrocatalysts for ORR. Rich N and S compounds in whey powders can generate abundant catalytic active sites. However, these sites are not easily accessible by reactants of ORR. A dual-template method was used to create a hierarchically and interconnected porous structure with micropores created by ZnCl₂ and large mesopores generated by fumed SiO₂ particles. At the optimum mass ratio of whey power: ZnCl₂  : SiO₂ at 1 : 3 : 0.8, the resulting carbon material has a large specific surface area close to 2000 m²  g^-1 , containing 4.6 at.% of N with 39.7% as pyridinic N. This carbon material shows superior electrocatalytic activity for ORR, with an electron transfer number of 3.88 and a large kinetic limiting current density of 45.40 mA cm^-2 . They were employed as ORR catalysts to assemble primary zinc-air batteries, which deliver a power density of 84.1 mW cm^-2 and a specific capacity of 779.5 mAh g^-1 , outperforming batteries constructed using a commercial Pt/C catalyst. Our findings open new opportunities to use an abundant biomaterial, whey powder, to create high-value-added carbon electrocatalysts for emerging energy applications.

Three-dimensional CoNi alloy nanoparticle and carbon nanotube decorated N-doped carbon nanosheet arrays for use as bifunctional electrocatalysts in wearable and flexible Zn-air batteries

A novel three-dimensional (3D) bifunctional electrocatalyst, CoNi alloy nanoparticle and carbon nanotube decorated N-doped carbon nanosheet arrays on carbon cloth (CoNi alloy/NCNSAs/CC) derived from polymetallic organic frameworks, is firstly prepared. The CoNi alloy/NCNSAs/CC-800 fabricated by pyrolyzing at 800 °C exhibits an oxygen reduction reaction (ORR, limiting current density) of 6.5 mA cm^-2 and a superior oxygen evolution reaction (OER, at 10 mA cm^-2) of 1.51 V, as well as a smaller potential difference of 0.676 V between OER and ORR half-wave potential, outperforming previous self-supporting cathodes. Flexible Zn-air batteries (FZABs) assembled with the CoNi alloy/NCNSAs/CC-800 exhibit higher energy density (98.8 mW cm^-2) and higher capacity (879 mAh g^-1), as well as excellent mechanical cycle ability (lower voltage gap of 0.66 V during the charge/discharge cycles at flat and folded state), significantly outstripping all other FZABs with self-supporting electrodes currently reported. Such a remarkable performance is ascribed to the 3D hierarchical nanostructure which promotes mass transport, the higher graphitization facilitating electronic mobility and the evenly dispersed active sites which accelerate kinetic reactions. So CoNi alloy/NCNSAs/CC-800 is a promising cathode candidate for ideal wearable energy devices and has great potential application in the field of electrochemical energy storage and conversion.

Bifunctional Catalysts for Reversible Oxygen Evolution Reaction and Oxygen Reduction Reaction

Metal-air batteries (MABs) and reversible fuel cells (RFCs) rely on the bifunctional oxygen catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Finding efficient bifunctional oxygen catalysts is the ultimate goal and it has attracted a great deal of attention. The dilemma is that a good ORR catalyst is not necessarily efficient for OER, and vice versa. Thus, the development of a new type of bifunctional oxygen catalysts should ensure that the catalysts exhibit high activity for both OER and ORR. Composites with multicomponents for active centers supported on highly conductive matrices could be able to meet the challenges and offering new opportunities. In this Review, the evolution of bifunctional catalysts is summarized and discussed aiming to deliver high-performance bifunctional catalysts with low overpotentials.

Rational Design of Unique ZnO/ZnS@N-C Heterostructures for High-Performance Lithium-Ion Batteries

Conversion-type anodes with high theoretical capacity have attracted enormous interest for lithium storage, although their extremely poor conductivity and volume variations during lithiation-delithiation processes seriously limit their practical applications. Herein, a facile strategy to fabricate ZnO/ZnS@N-C heterostructures decorated on carbon nanotubes (ZnO/ZnS@N-C/CNTs) with metal-organic framework assistance is developed. The as-prepared anodes display higher reversible capacity of 1020.6 mAh g^-1 at 100 mA g^-1 after 200 cycles and excellent high-cyclability with 386.6 mAh g^-1 at 1000 mA g^-1 over 400 cycles. The conductive CNT network and N-doped carbon shell could successfully improve the electrical conductivity and avoid the aggregation of ultrasmall ZnO/ZnS nanoparticles. The results calculated from density functional theory also suggest that the ZnO/ZnS heterostructures could promote electron-transfer capability.

Hybrid shells of N-doped carbon encapsulated by MnO nanoparticles as oxygen reduction reaction electrocatalysts

Recently, the development of non-precious metal electrocatalysts for effective oxygen reduction reaction (ORR) has become a research hotspot.

N-Doped carbon nanospheres with nanocavities to encapsulate manganese oxides as ORR electrocatalysts

MnO₂(Mn₃O₄or MnO) nanoparticles embedded in nanocavities of N-doped carbon nanospheres as ORR electrocatalysts have been reported.

Ultrafine cobalt nitride nanoparticles supported on carbon nanotubes as efficient electrocatalyst for rechargeable zinc-air batteries

Ultrafine (5 nm) cobalt nitride nanoparticles supported on carbon nanotubes (CoN/CNT) are reported as air electrodes for rechargeable zinc-air batteries (ZABs). CoN/CNT exhibits 2.4 fold higher battery performance than commercial Pt/C-IrO₂.

Long-Shelf-Life Polymer Electrolyte Based on Tetraethylammonium Hydroxide for Flexible Zinc-Air Batteries

Flexible zinc-air batteries (ZABs) have been considered as one of the most outstanding energy storage devices for flexible and portable electronics because of their superior energy density and environmental friendliness. As the "blood" of flexible ZABs, electrolytes play a significant role in determining their performance, such as discharge working time, cycling property, and shelf life. Herein, a novel polymer electrolyte based on quaternary ammonium hydroxides is first applied in flexible zinc-air batteries. Tetraethylammonium hydroxide (TEAOH) is innovatively used as the ionic conductor with poly(vinyl alcohol) (PVA) as the polymer host in the polymer electrolyte and exhibits a good water retention capability, resulting in not only a good shelf life but also a good working life of the flexible zinc-air batteries. The fabricated polymer electrolyte maintains its high ionic conductivity of 30 mS cm^-1 even after 2 weeks. In addition, the as-assembled zinc-air batteries based on the TEAOH-PVA electrolyte exhibit excellent discharge performance and cycling life compared to those based on the commonly used KOH-PVA electrolyte, and no notable degradation is observed after 2 weeks. Furthermore, flexible TEAOH-PVA-based zinc-air batteries can power a light-emitting diode (LED) electronic watch, a mobile phone, and an LED screen, indicating the very large potential of the high-performance zinc-air batteries that are safe, cost-effective, and remarkably flexible.

Three-Dimensional Fe,N-Decorated Carbon-Supported NiFeP Nanoparticles as an Efficient Bifunctional Catalyst for Rechargeable Zinc-O2 Batteries

The electro-catalyzed oxygen reduction and evolution reactions (ORR/OER) are the key elements of many energy conversion systems, such as fuel cells, water electrolyzers, and rechargeable metal-air batteries. Structural design of durable non-noble nanomaterials as bifunctional OER/ORR catalysts is a major drawback to commercial applications. Herein, we exposed a strongly coupled hybrid material comprising of NiFeP-cubes nanoparticles supported on three-dimensional interconnected Fe,N-decorated carbon (3D-FeNC) as a robust bifunctional ORR/OER catalyst. The strongly coupled NiFeP@3D-FeNC catalyst shows better electron and mass transfer capability, exposure of abundant ORR/OER active sites on the surface, and strongly coupled effects. Accordingly, the as-prepared NiFeP@3D-FeNC catalyst exhibits robust ORR activity (half-wave potential of 0.84 V vs reversible hydrogen electrode) and OER performance (over-potential 0.25 V@10 mA cm^-2) in alkaline media. Significantly, the oxygen electrode prepared from the NiFeP@3D-FeNC catalyst further demonstrated superior charge/discharge behavior and long-lasting rechargeability than the benchmark Pt/C + IrO₂ catalyst in rechargeable zinc-O₂ batteries. This approach opens up a new avenue for the synthesis and advanced the hybrid nanomaterials for various applications.

One-pot achievement of MnO2/Fe2O3 nanocomposites for the oxygen reduction reaction with enhanced catalytic activity

MnO₂/Fe₂O₃ nanocomposites were achieved in one-pot followed by high-temperature treatment, which presented excellent electrocatalytic activity for the oxygen reduction reaction.

A ternary MnO2-deposited RGO/lignin-based porous carbon composite electrode for flexible supercapacitor applications

MnO₂nanoparticles were successfully synthesized on a reduced graphene oxide/lignin-based porous carbon (RGO/PC) composite film by a simple electrodeposition method, and a ternary RGO/PC/MnO₂composite electrode for flexible supercapacitors was prepared.