Amino functionalized carbon nanotubes supported CoNi@CoO–NiO core/shell nanoparticles as highly efficient bifunctional catalyst for rechargeable Zn-air batteries

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the core reaction processes of rechargeable Zn-air battery (ZAB) cathode. Therefore, exploring a bifunctional catalyst with excellent electrochemical performance, high durability, and low cost is essential for rechargeable ZAB. In this work, amino functionalized carbon nanotubes supported core/shell nanoparticles composed of CoNi alloy core and CoO–NiO shell (CoNi@CoO–NiO/NH₂-CNTs-1) is synthesized through a simple and efficient hydrothermal reaction and calcination method, which shows higher ORR/OER bifunctional catalytic performance than the single metal-based catalyst, such as Ni@NiO/NH₂-CNTs and Co@CoO/NH₂-CNTs. The fabricated bimetallic alloy based catalyst CoNi@CoO–NiO/NH₂-CNTs-3 with the optimized loading content of CoNi@CoO–NiO core/shell nanoparticles, presents the best bifunctional catalytic performance for ORR/OER. Experimental studies reveal that CoNi@CoO–NiO/NH₂-CNTs-3 exhibits the onset potential of 0.956 V and 1.423 V vs. RHE for ORR and OER, respectively. It also exhibits a low overpotential of 377 mV to achieve a 10 mA cm^?2 current density for OER, and positive half-wave potentials of 0.794 V for ORR. And the potential difference between half-wave potential of ORR (E_1/2) and the potential at 10 mA cm^?2 for OER (E_j10) is 0.813 V. In addition, when CoNi@CoO–NiO/NH₂-CNTs-3 is used as an air electrode catalyst of rechargeable ZAB, its maximum power density and open circuit voltage (OCV) can reach 128.7 mW cm^?2 and 1.458 V (The commercially available catalyst of Pt/C–RuO₂ is 88.1 mW cm^?2), which strongly demonstrates that the fabricated catalyst CoNi@CoO–NiO/NH₂-CNTs-3 can be used as a highly efficient bifunctional catalyst for ZABs, and is expected to replace those expensive precious metal electrocatalysts to meet the growing demand for new energy devices.     

A robust bifunctional electrocatalyst for rechargeable zinc-air batteries: NiFe nanoparticles encapsulated in nitrogen-doped carbon nanotubes

Developing high-efficiency, low-cost, and stable bifunctional oxygen electrocatalysts is essential for the commercialization of rechargeable metal-air batteries. Herein, three-dimensional self-assembled microspheres via in situ encapsulation of NiFe alloy nanoparticles (NPs) into N-doping carbon nanotubes (NiFe@NCNTs) have been achieved through pyrolyzing a mixture of nickel-iron alkoxide and melamine. The as-prepared electrocatalyst exhibits outstanding oxygen reduction reaction (ORR) performance with a half-wave potential of 0.79 V and oxygen evolution reaction (OER) activity with a low overpotential of 330 mV at 10 mA cm^?2. The eminent activity of NiFe@NCNTs is ascribed to high dispersion of active sites (zero-dimensional core-shell structure of NiFe@NC) and one-dimensional conductive network (NCNTs). Accordingly, the zinc-air battery assembled with NiFe@NCNTs as the air cathode exhibits a long cycling life of 200 h with a high energy efficiency of 65.6%. This work may shed new light on the design of advanced bifunctional electrocatalysts toward metal-air batteries.     

Tunable Fe/N co-doped 3D porous graphene with high density Fe-Nx sites as the efficient bifunctional oxygen electrocatalyst for Zn-air batteries

Nitrogen-doped transition metal materials display promising potential as bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Fe/N co-doped three-dimensional (3D) porous graphene (FeN-3D-PG) is prepared via a template method using sodium alginate as the carbon source and low polymerization degree melamine resin as the nitrogen source. The low polymerization degree melamine resin can form complexes with Fe³⁺ in the aqueous solution and further forms high density Fe-N_x active sites during pyrolysis. Meanwhile, the formed 3D porous structure efficiently promotes the uniform distribution of Fe-N_x active sites. The FeN-3D-PG catalyst exhibits pH-independent ORR activity. For OER, the catalyst possesses a low over potential (370 mV at 10 mA cm⁻²) in alkaline electrolyte. The Zn-air batteries (ZABs) using FeN-3D-PG as cathode exhibits a power density up to 212 mW cm⁻², a high specific capacity of 651 mAh g⁻¹, and the charge-discharge stability of 80 h. This work provides new sight to transition metal materials based ZABs with excellent performance.     

Graphitic carbon-encapsulated cobalt nanoparticles embedded 1D porous hollow carbon nanofibers as advanced multifunctional electrocatalysts for overall water splitting and Zn-air batteries

Physical mixing of monofunctional noble metal catalysts, such as Pt/C or Ru/IrO₂, increases the commercial cost and stability risk of electrodes. Therefore, it is desirable to develop a multifunctional electrocatalyst for zinc-air batteries and integrated electrolytic devices. To develop an effective way to fabricate high-performance multifunctional electrocatalysts by modifying advanced nanostructures, a coaxial electrospinning approach with in-situ synthesis and subsequent carbonization was used to construct a highly integrated three-function catalyst composed of graphitic carbon-encapsulated cobalt nanoparticles embedded into one-dimensional (1D) porous hollow carbon nanofibers (CoNC-HCNFs). Under the synergistic effect of the active material and the advanced nanostructure, the as-prepared CoNC-HCNFs demonstrated an operating overpotential of 186 mV (10 mA cm^?2) for the hydrogen evolution reaction (HER), a half-wave potential of 0.83 V (vs. RHE at 10 mA cm^?2) for the oxygen reduction reaction (ORR), and a potential of 1.58 V (10 mA cm^?2) for the oxygen evolution reaction (OER). With their exceptional multifunctional activities, two CoNC–HCNF-based aqueous zinc-air batteries (ZABs) in series could drive an alkaline water electrolyzer for splitting water. Furthermore, due to the superior mechanical flexibility and rechargeability of the solid-state ZAB, it has great application prospects in powering portable and wearable electronics. This research is expected to offer inspiration for the development of other excellent MOF-based hollow carbon nanofibers and to enable them to be adopted more widely in electrochemical energy conversion and energy storage.     

Covalent organic polymer derived N–doped carbon confined FeNi alloys as bifunctional oxygen electrocatalyst for rechargeable zinc-air battery

N–doped carbon confined FeNi alloys are promising candidate to noble Pt and IrO₂ or RuO₂ for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable zinc-air batteries. However, it is difficult to control the distribution of transition metals in the precursor and electrocatalyst. Herein, we design a covalent organic polymer to realize the uniform distribution of metal, nitrogen and carbon precursors. The structure of the obtained electrocatalyst is FeNi nanoparticles coated with carbon shells dispersed on N-doped multilayer porous carbon (FeNi@NC). The resultant FeNi@NC delivered a half-wave potential for ORR of 0.878 V and a low potential of 1.59 V to achieve 10 mA cm^?2 for OER, which surpasses commercial platinum/carbon and ruthenium dioxide. The outstanding bifunctional properties of FeNi@NC attribute to the synergistic coupling between N-doped carbon shells and dense FeNi nanoparticles. Moreover, the self-made zinc-air battery with FeNi@NC air-cathode displayed an excellent energy density of 137.7 mW cm^?2 as well as cycling stability (100 h, 200 cycles).     

Top-down preparation of Ni–Pd–P@graphitic carbon core-shell nanostructure as a non-Pt catalyst for enhanced electrocatalytic reactions

Electrochemical reactions such as the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and methanol oxidation reaction (MOR) are essential for energy conversion applications such as water electrolysis and fuel cells. Furthermore, Pt or Ir-related materials have been extensively utilized as electrocatalysts for the OER, ORR, and MOR. To reduce the utilization of precious metals, innovative catalyst structures should be proposed. Herein, we report a bi-metallic phosphide (Ni₂P and PdP₂) structure surrounded by graphitic carbon (Ni–Pd–P/C) with an enhanced electrochemical activity as compared to conventional electrocatalysts. Despite the low Pd content of 3 at%, Ni–Pd–P/C exhibits a low overpotential of 330 mV at 10 mA cm^?2 in the OER, high specific activity (2.82 mA cm^?2 at 0.8 V) for the ORR, and a high current density of 1.101 A mg^?1 for the MOR. The superior electrochemical performance of Ni–Pd–P/C may be attributed to the synergistic effect of the bi-metallic phosphide structure and core-shell structure formed by graphitic carbon.     

Co,N co-doped carbon nanosheets coupled with NiCo2O4 as an efficient bifunctional oxygen catalyst for Zn-air batteries

Developing of inexpensive and efficient bifunctional oxygen catalysts is important for the zinc-air batteries (ZABs). Here, a composite of Co, N co-doped carbon nanosheets coupled with NiCo₂O₄ (NiCo₂O₄/CoNC-NS) is developed as oxygen catalyst, which has good bifunctional oxygen catalytic activity and durability. Specifically, the half-wave potential of oxygen reduction reactions (ORR) is 0.849 V, and the overpotential of oxygen evolution reactions (OER) is 1.582 V at a current density of 10 mA cm⁻². And the assembled liquid ZABs based on NiCo₂O₄/CoNC-NS exhibit high open circuit potential (OCP, 1.482 V), high peak power density (148.3 mW cm⁻²) and large specific capacity (699.9 mAh g⁻¹) with long-term stability. Moreover, the further assembled solid ZABs can also provide high OCP (1.401 V), good power density (58.1 mW cm⁻²) and superior stability. This work would provide a good reference for the development of other advanced oxygen catalyst in future.     

Mn/Cu nanoclusters-grafted N-doped carbon nanotubes: Robust oxygen electrode catalysts for Zn-air batteries

Developing efficient nonprecious electrocatalysts that can drive the oxygen electrode reactions in zinc-air batteries (ZABs) is important but remains challenging. In this work, novel materials comprising Mn/Cu nanoclusters-grafted N-doped carbon nanotubes are synthesized by preparing and then pyrolyzing Mn/Cu polyphthalocyanine-encapsulated carbon nanotubes (CNTs), followed by treating the products with acidic solution. The materials are named CNTs@(Mn,Cu)PPc-T, where T denotes the pyrolysis temperature in °C, and they are demonstrated to serve as efficient oxygen electrode catalysts for zinc-air batteries (ZABs). Among them, the one synthesized at 900 °C, CNTs@(Mn,Cu)PPc-900, requires more positive onset and half-wave potentials for reduction of oxygen and a low overpotential for the evolution of oxygen. A rechargeable ZAB assembled with CNTs@(Mn,Cu)PPc-900 electrocatalyst delivers a high power density (158.5 mW cm⁻²) and displays an excellent stability in 200 cycles of charge/discharge (in over 33 h). Such performance is even superior to that of a ZAB containing the benchmark Pt/C + RuO₂ catalyst as an air cathode under identical testing condition.     

PBA derived FeCoP nanoparticles decorated on NCNFs as efficient electrocatalyst for water splitting

Transition metal phosphides have been known as promising electrocatalysts for hydrogen evolution and oxygen evolution reactions (HER and OER) due to their high catalytic activity. In this work, the FeCoP nanoparticles decorated on N-doped electrospun carbon nanofibers (FeCoP@NCNFs) was successfully synthesized through depositing Fe, Co-based Prussian blue analogue Co₃[Fe(CN)₆]₂·10H₂O (FeCo-PBA) onto the electrospun PVP/PAN nanofibers via layer-by-layer approach, followed by carbonization and phosphorization treatments. Benefiting from the high electrical conductivity, abundant catalytic active sites and the synergistic effect between FeCoP nanoparticles and N-doped carbon nanofibers network, the obtained FeCoP@NCNFs displays good bifunctional electrocatalytic activity. In 1 M KOH, the FeCoP@NCNFs achieves 10 mA cm^?2 at an overpotential of 290, 226 mV for OER and HER, respectively. Moreover, it demands overpotential of 196 mV to achieve 10 mA cm^?2 for HER in 0.5 M H₂SO₄. The FeCoP@NCNFs is used as both anode and cathode for overall water splitting, it requires a low voltage of 1.65 V to achieve a current density of 10 mA cm^?2 and maintains outstanding stability over 10 h. Herein, a strategy for preparing bifunctional electrocatalysts of compositing transition metal phosphides with carbon nanofibers is proposed, and the application of metal-organic framework in electrocatalytic field is further extended.     

Promotional effects of trace Ni on its dual-functional electrocatalysis of Co/N-doped carbon nanotube catalysts for ORR and OER

It is still a great challenge for developing efficient dual-functional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalysts are critical to enhance the efficiency of metal-air cells and fuel cells. In this study, a one-pot vapor deposition method was used to realize the synchronously dope of N and Ni (trace) into Co/C to form Co–Ni (trace)/N-doped carbon nanotubes (Co–Ni (trace)/NCNTs). An interesting result is that injecting dicyandiamide (DCD) into Ni foam as a precursor led to the in situ formation of NCNTs, with synchronous doping of trace Ni into Co species. The cooperative effects of the Co–Ni (trace) and N-doped carbon nanotubes resulted in superior dual-functional electrocatalytic performance of Co–Ni (trace)/NCNTs for the ORR (half-wave potential E_1/2 vs. RHE: 0.83 V, electron transfer number n: 3.97) and OER (overpotential vs. RHE: 337 mV at 10 mA cm^?2, Tafel slope: 94.0 mV dec^?1). Moreover, the Co–Ni (trace)/NCNTs catalyst showed excellent stability during 20,000 s of durability testing for both ORR and OER. This study provides a feasible strategy for designing efficient nonnoble metal-catalysts for renewable energy conversion devices.     

Pulse-electrodeposited Ni–Fe–Sn films supported on Ni foam as an excellent bifunctional electrocatalyst for overall water splitting

The development of extremely active bifunctional non-noble electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is pivotal for water splitting but remains challenging. Herein, self-supported Ni–Fe–Sn electrocatalysts were fabricated on nickel foam (NF) through a simple and facile pulse electrodeposition process. Under optimal conditions, the prepared Ni–Fe–Sn electrocatalysts exhibited excellent bifunctional properties in alkaline medium and required ultralow overpotentials of only 27 and 201 mV for HER and OER, respectively, to reach the current density of 10 mA cm^?2. Importantly, the same Ni–Fe–Sn electrocatalyst can be assembled as the anode and the cathode in a two-electrode system. It demanded a fairly low applied voltage of 1.55, 1.72, and 1.87 V to produce 10, 50, and 100 mA cm^?2, respectively, and exhibited excellent long-term stability. The excellent electrocatalytic water splitting performance of the Ni–Fe–Sn film was mainly associated with its intrinsic catalytic activity derived from the modulation of the electronic structures among Ni, Fe, and Sn by using the appropriate atomic ratio of Ni: Fe: Sn.     

An efficient metal-free bifunctional oxygen electrocatalyst of carbon co-doped with fluorine and nitrogen atoms for rechargeable Zn-air battery

It is highly critical to explore efficient bifunctional oxygen electrocatalysts for regenerative fuel cells and metal-air batteries. Herein, N, F co-doped carbon material (NF@CB) was synthesized as metal-free efficient bifunctional electrocatalysts by directly pyrolyzing a mixture of carbon black, polytetrafluoroethylene and melamine. Benefiting from the synergistic effects between N and F atoms, NF@CB exhibits a positive half-wave potential (E_1/2) of 0.814 V (vs. RHE) for oxygen reduction reaction, and an operating potential (E₁₀) of 1.609 V at 10 mA cm⁻² for oxygen evolution reaction in alkaline electrolyte. The bifunctional oxygen electrocatalytic activity index (ΔE = E₁₀−E_1/2) is 0.795 V, which is notably better than that of the single N-doped carbon (1.238 V), and similar to that of the commercial Pt/C and RuO₂ mixture catalyst (0.793 V). Impressively, the assembled Zn-air battery (ZAB) with NF@CB as an air-electrode catalyst displays a small charge/discharge voltage gap of 0.852 V at 20 mA cm⁻². Moreover, the NF@CB catalyzed ZAB exhibits good rechargeability and long-lasting cycling stability with over 49 h. This investigation introduces a cheap and simple way to develop highly efficient bifunctional N, F co-doped electrocatalysts.     

In-situ construction and activities of La0·8Sr1·2Fe0·5Ni0·5O4+δ@CNTs hybrids as bifunctional oxygen catalysts

Perovskite oxides are proved to be promising oxygen bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Constructing a perovskite oxide/carbon composite with intimate interaction at the interface is of great importance for conductivity and bifunctional oxygen activities. In this work, combining “exsolution effect” of perovskite oxide at high temperature and reducing atmosphere, carbon nanotubes (CNTs) are in-situ synthesized on the surface of a La_0·8Sr_1·2Fe_0·5Ni_0·5O_4+δ (LSFN) perovskite oxide with K₂NiF₄ structure via a simple chemical vapor deposition (CVD) method. Physical characterizations show that CNTs are twining around the surface of LSFN particles with strong interaction. Under the function of synergistic effect between LSFN and CNTs, more mobile oxygen species, improved surface electronic structure and optimized charge distribution and transformation are obtained. Finally, the as-prepared LSFN@CNTs composites exhibit superior oxygen electrocatalytic performances in alkaline solution, with an ORR overpotential of 761 mV at ?1.0 mA cm^?2, a small OER overpotential of 314 mV at 10 mA cm^?2 and an enhanced cycling stability of >3000 cycles, which outperforms commercial IrO₂ catalyst and published perovskite oxide based bifunctional oxygen catalysts.     

High active and ultra-stable bifunctional FeNi/CNT electrocatalyst for overall water splitting

Efficient non-noble metal catalysts are desirable to greatly improve the efficiency of anodic oxygen evolution and cathodic hydrogen evolution reactions. Herein, iron-nickel/carbon nanotube composites are synthesized as efficient bifunctional electrocatalysts for water splitting. The catalyst is homogeneously distributed, while the formation of iron-nickel alloy is confirmed. Because of the synergism of iron and copper and the contribution of carbon nanotubes, the Fe–Ni/CNT electrocatalyst shows excellent oxygen evolution reaction performance with the overpotential of 221 mV at 10 mA cm^?2 and maintains stable at 0.48 V for 150 h. It expedites overall water splitting at 10 mA cm^?2 with 1.50 V and show excellent stability at 20 mA cm^?2 for 65 h, providing great potential for large-scale applications.     

Bifunctional nanoporous ruthenium-nickel alloy nanowire electrocatalysts towards oxygen/hydrogen evolution reaction

A class of ruthenium-nickel alloy catalysts featured with nanoporous nanowires (NPNWs) were synthesized by a strategy combining rapid solidification with two-step dealloying. RuNi NPNWs exhibit excellent electrocatalytic activity and stability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in which the RuNi-2500 NPNWs catalyst shows an OER overpotential of 327 mV to deliver a current density of 10 mA cm^?2 and the RuNi-0 NPNWs catalyst requires the overpotential of 69 mV at 10 mA cm^?2 showing the best HER activity in alkaline media. Moreover, the RuNi-1500 NPNWs catalyst was used as the bifunctional electrocatalyst in a two-electrode alkaline electrolyzer for water splitting, which exhibits a low cell voltage of 1.553 V and a long-term stability of 24 h at 10 mA cm^?2, demonstrating that the RuNi NPNWs catalysts can be considered as promising bifunctional alkaline electrocatalysts.     

Y and Fe co-doped LaNiO3 perovskite as a novel bifunctional electrocatalyst for rechargeable zinc-air batteries

Perovskite oxides are widely regarded as the promising air electrode catalytic materials for zinc-air batteries (ZABs). In the present work, A-site Y and B-site Fe co-doped La_0.85Y_0.15Ni_0.7Fe_0.3O₃ perovskite catalyst was prepared by self-propagating high-temperature synthesis, and this material was evaluated as a bifunctional electrocatalyst for ZABs. The effect of co-doping on crystal structure and reaction activities, which can promote oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), was investigated. Results show that Y and Fe co-doping substantially improved the ORR and OER of LaNiO₃. In comparison with LaNiO₃, the ORR performance of La_0.85Y_0.15Ni_0.7Fe_0.3O₃ exhibited a higher limiting current density (3.8 mA cm^?2 at 0.4 V vs. RHE) and more positive onset potential (0.75 V vs. RHE) at 1600 rpm. It also had an excellent OER performance of 1.74 V vs. RHE at 10 mA cm^?2. When La_0.85Y_0.15Ni_0.7Fe_0.3O₃ was used as an air electrode catalyst for ZABs, it exhibited a high power density of 93.6 mW cm^?2, which increased by 84.8% compared with that of LaNiO₃. Moreover, the full cell with La_0.85Y_0.15Ni_0.7Fe_0.3O₃ air electrode catalyst was operated for more than 80 h, maintaining good stability. Therefore, La_0.85Y_0.15Ni_0.7Fe_0.3O₃ can be used as a promising bifunctional air electrode catalyst for ZABs. The characterization analysis reveals that A-site Y and B-site Fe co-doped catalyst transforms crystal structure from trigonal system to cubic system, retain the valence state of Ni³⁺ and increases the contents of O₂^2?/O^?, and these properties are more conducive for LaNiO₃ catalysis.     

One-step synthesis of carbon-encapsulated nickel phosphide nanoparticles with efficient bifunctional catalysis on oxygen evolution and reduction

As a promising and cost-efficient alternative to noble metal catalysts, transition metal phosphides (TMPs) show highly catalytic performance toward oxygen reduction and evolution reactions (ORR and OER). Mesoporous carbon-coated nickel phosphide (NiP) nanoparticles were successfully synthesized by thermal decomposition at 500 °C under N₂/H₂ (95:5) atmosphere. The NiP/C hybrid exhibits excellent OER/ORR activity. It can generate an OER current density of 10 mA cm^?2 at the overpotential of 0.26 V with a low Tafel slope of 43 mV dec^?1, and produce a limited ORR current density of 5.10 mA cm^?2 at 1600 rpm with a half-wave potential of 0.82 V via a 4-electron pathway. In addition, the OER/ORR catalytic currents remain considerable stable without significant loss for more than 25 h polarization. This work will open up a new avenue to design a bifunctional catalyst with a superior OER/ORR activity and stability, and this cost-efficient strategy will pave the way for the industrial application of the renewable energy technologies.     

Impact in rational synthesis Co-ZIF templates for derived the structural Co@NC catalysis for high efficient hydrogen and oxygen evolution reactions

Developing highly active and stable non-noble metal bifunctional electrocatalysts are urgently demanded in overall water splitting. Herein, tunable precursor ratio synthesis of cobalt-based ZIFs as a template derived active cobalt embedded N-doped carbon (Co@NC) catalyst. The rational synthesis of ZIF templates significantly impacts the complex nanostructure and properties of the catalyst (Co@NC). Consequently, the different nanostructures on Co@NC exhibit significance for the electrocatalyst of hydrogen and oxygen evolution reactions. The optimized Co@NC-20 provides excellent electrocatalytic activity with the lowest overpotential of 172 and 301 mV for HER and OER, respectively, at the current density of 10 mA cm^?2. The bifunctional Co@NC-20 reveals a potential for overall water splitting as low as 1.68 V of 10 mA cm^?2. After continuously working for 24h, the exceptional stability activity maintains 75% of the catalytic performance on Co@NC-20. The beneficial character in the synergistic effects between high-active Co species with well-protection of the metal core by carbon shell promotes their excellent performance. This study provides an essential reference for the rational design of ZIF templates for electrocatalysts with more complex structures in the future.     

Efficient MnO and Co nanoparticles coated with N-doped carbon as a bifunctional electrocatalyst for rechargeable Zn-air batteries

Developing the low-cost, durable, and efficient bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays an important role in the commercial implementation of the Zn-air batteries. Herein, we design and synthesize the MnO and Co nanoparticles coated with N-doped carbon (MC@NC) as an excellent bifunctional oxygen electrocatalyst. It is found that the optimal MC@NC-0.3 exhibits outstanding ORR performance with a positive half-wave potential of 0.82 V and excellent OER activity with a small overpotential of 360 mV at 10 mA cm⁻². When applied in the liquid Zn-air battery, MC@NC-0.3 displays a high maximum power density of 153 mW cm⁻², a large specific capacity of 776 mAh g⁻¹ and the excellent cycling stability with a negligible increase after 300 h. Furthermore, the fiber-shaped all-solid-state Zn-air battery also displays remarkable stability at high current density. This study offers a facile strategy to construct a high-efficient, low-cost, and durable transitional metal-based bifunctional electrode for renewable energy applications.     

Oxygen plasma induced interfacial CoOx/Phthalocyanine Cobalt as bifunctional electrocatalyst towards oxygen-involving reactions

Performance of electrocatalysts towards oxygen-involving reactions is strongly associated with the surface and interface properties. Cobalt phthalocyanine (CoPc) materials have been widely explored as oxygen-involving electrocatalysts but their intrinsic catalytic activity is always poor. We present here a surface oxygen plasma approach to directly treat CoPc for producing interfacial CoO_x nanodots anchored on CoPc (CoO_x/CoPc), which exhibits high activity towards both oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). The optimized CoO_x/CoPc demonstrates a much better catalytic activity with a half-wave potential of 0.63 V and an average electron transfer number of 3.64 than the CoPc (0.59 V and n = 2.37) towards ORR in alkaline media. Moreover, OER performance of the CoO_x/CoPc is also significantly enhanced, showing a current density of 22.2 mA cm^?2 that is 36 times higher than that of CoPc (0.6 mA cm^?2) at an overpotential of 0.49 V. It is found that the enhanced performance of the CoO_x/CoPc is attributed to the high electrochemical active surface area, highly active CoO_x, as well as desired interfacial structure.