High-efficiency Bifunctional Electrocatalysts Research Articles

Heterointerface engineering of yolk-shell-structured Mn2O3/RuO2 for boosting oxygen electrocatalysis in rechargeable liquid and flexible zinc-air batteries

Rational construction of high-efficient bifunctional oxygen electrocatalysts is of crucial significance for rechargeable Zn-air batteries (ZABs). Here, the yolk-shell-structured Mn2O3/RuO2 heterojunction is purposely constructed via the Kirkendall effect as a robust bifunctional oxygen electrocatalyst for simultaneously driving oxygen evolution and reduction reactions (OER and ORR). The strong interactions between Mn2O3 and RuO2 induces the surface reconstruction that brings the electronic transfer from Mn to Ru, and the changes of coordination environments of metal atoms. Meanwhile, the yolk-shell structure enables maximum contact of the active sites with the electrolyte and prevents the dissolution and peroxidation of active species. As a result, the yolk-shell-structured Mn2O3/RuO2 shows an outstanding bifunctional activity with a very low potential gap of ΔE = 0.60 V. Moreover, the ZABs assembled with Mn2O3/RuO2 render a large open circuit voltage of 1.53 V, a high specific capacity of 742.1 mA h g−1 and an exceptional cycling stability over 850 h that significantly outperforms those of Pt/C+RuO2-based ZABs. Moreover, the self-made flexible solid-state ZAB with Mn2O3/RuO2 cathode also shows good charge–discharge reversibility and flexibility at different bending angles. This work provides a feasible method for the design of efficient oxygen electrocatalysts to promote the practical application of ZABs.

Strong electronic interaction in chromium-molybdenum dual incorporated few-layer cobalt sulfide nanosheets with lattice distortion for efficient bifunctional water splitting

The investigation into cost-effective and high-efficiency bifunctional electrocatalysts for electrochemical water splitting is crucial for advancing the conversion efficiency of intermittent energy systems. In this study, a novel dissolution-in situ precipitation method is introduced to synthesize few-layer CoS2 nanosheets incorporating dual cations (Cr, Mo), referred to as Cr/Mo-CoS2. The synergistic influence arising from robust dual dopant-induced coupling interactions and pronounced lattice distortions enhances the rate-determining steps of the HER and OER processes in Cr/Mo-CoS2 by optimizing the adsorption of H* and OOH* intermediates on the catalyst surface. The distinctive pinecone-like structure formed by these nanosheets provides numerous active sites and facilitates electron transfer during reactions. Consequently, the synthesized Cr/Mo-CoS2 nanosheets demonstrate superior catalytic activity, characterized by a low overpotential of 123.8 mV at 10 mA cm−2 for the hydrogen evolution reaction and 310.2 mV at 50 mA cm−2 for the oxygen evolution reaction, coupled with excellent durability in alkaline electrolytes. When utilized as bifunctional electrodes for comprehensive water splitting, Cr/Mo-CoS2 achieves a current density of 10 mA cm−2 at a cell voltage of 1.55 V. This research underscores the critical role of dual-cation doping-induced coupling interactions and significant lattice distortions in augmenting the performance of transition metal chalcogenide electrocatalysts.

In-situ construction of integrated transition metals and metal oxides with carbon nanomaterial heterostructures to modulate electron redistribution for boosted water splitting

Heterostructure engineering has been proposed as a promising approach to construct high-efficiency bifunctional electrocatalyst for overall water splitting. Integrated transition metal and metal oxide heterointerfaces with carbon nanomaterials are designed to facilitate electrocatalytic performance toward overall water splitting. Fe/MnO heterostructures are fabricated on graphene using a one-step DC arc plasma technology. In this way, increased electrochemically active specific areas, accelerated charge transfer, and proper interfacial electronic structure can be achieved. Benefiting from the synergistic effect of multiple materials, fabricated Fe/MnO/graphene heterointerfaces can make the redistribution of electrons between heterointerfaces, which effectively optimizes adsorption/desorption energy of the reaction intermediates. Fe/MnO/graphene delivers excellent catalytic activity with only 362 mV and 339 mV overpotential to reach current density of 10 mA cm−2 for OER and HER and exceptional long-term stability in alkaline solution. As electrocatalyst at both the cathode and the anode of an alkaline electrolyzer simultaneously, Fe/MnO/graphene electrocatalyst requires a cell voltage of 1.987 V at a current density of 10 mA cm−2 for overall water splitting. Therefore, this work offers a feasible route to construct hierarchically nanohybrids as bifunctional electrocatalysts by combining transition metal and metal oxide with carbon nanomaterials.

Customizing oxygen electrocatalytic microenvironment with S, N codoped carbon nanofibers confining carbon nanocapsules and Co9S8 nanoparticles for rechargeable Zn-air batteries

Rational design and modulation of oxygen electrocatalytic microenvironment are crucial for achieving high performance in rechargeable Zn-air batteries (RZABs). We report a high-efficiency bifunctional electrocatalyst based on S, N codoped carbon fibers confining carbon nanocapsules attached with Co9S8 nanoparticles to customize the oxygen electrocatalytic microenvironment. The inner carbon nanocapsules function as a “gas buffer”, while the outer fiber skeleton acts as a self-supporting structure, which jointly refine the oxygen electrocatalytic microenvironment and improve accessibility of the active sites. Such a unique nanostructure proves advantageous for O2 adsorption/diffusion and mitigation of local pH changes during oxygen reduction reaction, and favors the release of generated O2 and the transfer of interfacial electron during the oxygen evolution reaction as well. The constructed liquid RZABs deliver a large peak power density (280 mW cm−2) and robust cyclability (1200 h at 10 mA cm−2), and the assembled quasi-solid state flexible RZABs further indicate long-term durability.

Manipulating d-d orbital hybridization induced by Mo-doped Co9S8 nanorod arrays for high-efficiency water electrolysis

Precisely refining the electronic structure of electrocatalysts represents a powerful approach to further optimize the electrocatalytic performance. Herein, we demonstrate an ingenious d-d orbital hybridization concept to construct Mo-doped Co9S8 nanorod arrays aligned on carbon cloth (CC) substrate (abbreviated as Mo-Co9S8@CC hereafter) as a high-efficiency bifunctional electrocatalyst toward water electrolysis. It has experimentally and theoretically validated that the 4d-3d orbital coupling between Mo dopant and Co site can effectively optimize the H2O activation energy and lower H* adsorption energy barrier, thereby leading to enhanced hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. Thanks to the unique electronic and geometrical advantages, the optimized Mo-Co9S8@CC with appropriate Mo content exhibits outstanding bifunctional performance in alkaline solution, with the overpotentials of 75 and 234 mV for the delivery of a current density of 10 mA cm−2, small Tafel slopes of 53.8 and 39.9 mV dec−1 and long-term stabilities for at least 32 and 30 h for HER and OER, respectively. More impressively, a water splitting electrolylzer assembled by the self-supported Mo-Co9S8@CC electrode requires a low cell voltage of 1.53 V at 10 mA cm−2 and shows excellent stability and splendid reversibility, demonstrating a huge potential for affordable and scalable electrochemical H2 production. The innovational orbital hybridization strategy for electronic regulation herein provides an inspirable avenue for developing progressive electrocatalysts toward new energy systems.

Hydrophobic-aerophilic composite catalysts enable the fast-charging Zn-air battery to operate 1200 h at 50 mA cm−2

High-efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are central to Zn-air batteries (ZABs). However, the bifunctional activity of catalysts is still unsatisfactory, which restricts the fast-charge performance of ZABs. In this work, we constructed a hydrophobic-aerophilic bifunctional catalyst, where CoFe nanoparticles (NPs) and single atoms (SAs) are separately loaded on zeolite imidazolate fame (ZIF)-derived carbon and hollow carbon tubes respectively (CoFe NP@SA). Thereinto, CoFe SAs are known to be highly active to ORR reaction. Moreover, the in-situ Raman illustrates that CoFe NPs are transformed to CoOOH and FeOOH by electrochemical reconstruction, which can boost the OER activity. Furthermore, the hydrophobic-aerophilic surface can repel water molecules to create abundant solid–liquid-gas three-phase reaction interfaces and expose active sites, which consequently promote the diffusion of reactive molecules/ions across the interface and the oxygen adsorption. Thus, the CoFe NP@SA catalyst exhibit an ultralow ORR/OER potential gap of 0.6 V. After assembled as zinc-air battery (ZAB), it demonstrates a low charge potential (2.09 V) under a high current density of 50 mA cm−2 with the 1200-hour durability. This strategy paves the way to realize the high-power-density and fast-charging ZABs.

Modulating electronic structure of nickel diselenide by vanadium doping toward highly efficient and stable bifunctional electrocatalysts for overall water splitting

Designing low-cost and high-efficiency bifunctional electrocatalysts is one of the challenges in the clean production of hydrogen energy in electrochemical water splitting. Transition metal selenides (TMSes) have been widely studied because of their low price, intrinsic metal properties, and high catalytic activity. In addition, the synergistic effect between bimetallic selenides exhibits better performance than monometallic selenides in the electrocatalytic process. Herein, we synthesized V-doped NiSe2 nanowire arrays on pretreated nickel foam by a convenient two-step hydrothermal synthesis method. In the alkaline electrolyte, V-NiSe2/NF exhibited excellent OER catalytic activity (293.6 mV@50 mA cm–2). In addition, the introduction of heteroatom V induces stronger electronic interactions between the structural atoms of the catalyst, altering the electronic structure and causing V-NiSe2/NF to demonstrate excellent OER performance. In the long-term OER test, V-NiSe2/NF was converted into NiOOH and SeOx2–, which may be the “real” active species during catalytic reactions, and we also successfully captured the formation of intermediate NiOOH and selenite as active centers in the OER process through in-situ Raman. The theoretical calculation shows that the electron transfer modulates the electron structure, changes the adsorption-desorption energy of the reaction intermediates, reduces the potential barrier of the rate-limiting step, and improves the OER activity. The V doping engineering strategy and the unique nanowire array structure make TMSes exhibit excellent OER performance. This study provides a new idea for the design of TMSe catalysts with excellent electrocatalytic performance.

Nickel Nanoparticles Protruding from Molybdenum Carbide Micropillars with Carbon Layer-Protected Biphasic 0D/1D Heterostructures for Efficient Water Splitting.

It remains a tremendous challenge to achieve high-efficiency bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) for hydrogen production by water splitting. Herein, a novel hybrid of 0D nickel nanoparticles dispersed on the one-dimensional (1D) molybdenum carbide micropillars embedded in the carbon layers (Ni/Mo2C@C) was successfully prepared on nickel foam by a facile pyrolysis strategy. During the synthesis process, the nickel nanoparticles and molybdenum carbide were simultaneously generated under H2 and C2H2 mixed atmospheres and conformally encapsulated in the carbon layers. Benefiting from the distinctive 0D/1D heterostructure and the synergistic effect of the biphasic Mo2C and Ni together with the protective effect of the carbon layer, the reduced activation energy barriers and fast catalytic reaction kinetics can be achieved, resulting in a small overpotential of 96 mV for the HER and 266 mV for the OER at the current density of 10 mA cm-2 together with excellent durability in 1.0 M KOH electrolyte. In addition, using the developed Ni/Mo2C@C as both the cathode and anode, the constructed electrolyzer exhibits a small voltage of 1.55 V for the overall water splitting. The novel designed Ni/Mo2C@C may give inspiration for the development of efficient bifunctional catalysts with low-cost transition metal elements for water splitting.

Engineering hierarchical snowflake-like multi-metal selenide catalysts anchored on Ni foam for high-efficiency and stable overall water splitting.

The development of excellent bifunctional electrocatalysts is an effective way to promote the industrial application of electrolytic water. In this work, a free-standing W-doped cobalt selenide (W-CoSe300/NF) electrocatalyst with a snowflake-like structure supported on nickel foam was prepared by a hydrothermal-selenization strategy. Benefiting from the high specific surface area of the 3D snowflake-like structure and the regulation of tungsten doping on the electronic structure of the metal active center, W-CoSe300/NF shows remarkable electrocatalytic water decomposition performance. In 1.0 M KOH, the W-CoSe300/NF electrocatalyst achieved an efficient HER and OER at a current density of 50 mA cm-2 with overpotentials as low as 84 mV and 283 mV, respectively. More importantly, W-CoSe300/NF acts as both the anode and cathode of the electrolytic tank, requiring only a potential of 1.54 V to obtain 10 mA cm-2 and can operate continuously for more than 120 hours at this current density. This study proposes a new way for the design of high efficiency and affordable bifunctional electrocatalysts.

Dual-carbon coupling modulated bimetallic sulfides as high-efficiency bifunctional oxygen electrocatalysts in a rechargeable Zn–air battery

A hybrid of bimetallic sulfides modulated by 1D/2D carbon displays highly efficient bifunctional electrocatalytic performance for the ORR/OER in a rechargeable Zn–air battery.

Promoting the activity of Ni3S2-x/Ni2P fuzzy-like nanorods as a bifunctional electrocatalyst for efficient overall water splitting through dealloying and active site design strategy

High-efficiency bifunctional electrocatalysts can reduce the hydrogen and oxygen evolution reaction (HER/OER) overpotential, which is of great significance for hydrogen production by water splitting. However, issues remain with large-scale preparation and a bottleneck for design separation. In this work, we reported on a facile method using a nanostructured transition metal sulfide (TMS) Ni3S2-Vs-Ps nanorod (NSVP NR) bifunctional catalyst material, which was prepared by dealloying and doping to obtain novel fuzzy-like NRs with heterostructures in triphasic points. The experimental results and first-principles calculations both revealed that the P-dopants changed the coordination environment between the inner S-vacancy Ni3S2-x NRs and outer Ni2P nanoparticles in the heterojunctions of the triphasic points, which as active sites could accelerate the movement of electron charges in the metal catalyst. The NVSP NRs showed excellent adsorption energy results, which on the Ni site were ΔGH* at 0.12 eV for HER and ΔGmax at 0.48 eV for OER. The optimized NSVP NRs demonstrated a current density of 100 mA/cm2 at the lowest overpotential of only 148 mV for HER and 311 mV for OER. Moreover, a cell voltage of 1.565 V could achieve 10 mA/cm2 when assembled in 1 M KOH solution for overall water splitting (OWS). Therefore, these findings provide a novel route from traditional dealloying corrosion for creating nanostructures and for producing new energy, offering insight into bifunctional catalyst design and application.

Self-supported bifunctional W-MoS2/FeNi2S4/NF electrodes with superhydrophilicity and superaerophobicity surface for intermittent energy-driven electrocatalytic overall water splitting

As energy scarcity and environmental pollution become increasingly problematic, developing non-polluting and sustainable hydrogen production technologies is crucial, with an emphasis on developing high-efficiency and easily available electrolytic hydrocatalysts. Herein, we present a novel, economical self-supporting electrode, W-MoS2/FeNi2S4/NF, fabricated by a simple hydrothermal method. Benefiting from the insitu growth of uniformly dispersed micro- and nanoparticles with an ultrathin nanosheet-like shape on the surface and heterogeneous engineering and heteroatom doping, the catalytic electrodes possess surface superhydrophilic/underwater superaerophobic properties and superb intrinsic catalytic activity. The superhydrophilic/underwater superaerophobic properties of the catalytic electrodes allow for rapid infiltration of the electrolyte solution into the electrode and accelerate mass transfer while also allowing for the desorption of bubbles from the electrode surface and avoiding the bubble shielding effect, resulting in a significantly increased electrocatalytic rate. With current densities as high as 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, W-MoS2/FeNi2S4/NF displayed lower overpotentials of 92 and 177 mV. More impressively, only a low cell voltage of merely 1.5 V is sufficient to achieve a current density of 10 mA cm−2, achieve overall water splitting in an alkaline electrolyte, and exhibit up to 20 h electrochemical durability. Above all, it has been demonstrated that surplus electricity from intermittent energy sources may be used to create eco-friendly hydrogen energy by electrolyzing water, preventing resource waste. This work provides novel insights into the preparation of inexpensive, high-efficiency bifunctional electrocatalysts and new directions for intermittent energy generation for hydrogen production.

Boosting the bifunctional electrocatalytic activity of nitrogen-doped graphene by electronic effect of heterovalent ion substituted perovskite oxides

Sluggish reaction kinetics of carbon-based catalysts hinder their activity in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which further impede commercialization of Zinc-air batteries. Here, a strategy of modifying the electronic structure of nitrogen-doped graphene (NG) through constructing it with cobalt (Co) substituted manganese-based perovskite oxides (LaMn1-xCoxO3) to accelerate its activity in OER and ORR is proposed. Co substitution is beneficial for donating electrons to oxygen-containing intermediates by inducing excessive negative charge on NG to improve kinetics in OER and ORR. The half-wave potential in ORR for LaMn0·6Co0·4O3@NG is 0.74 V, higher than that of LaMnO3@NG and LaCoO3@NG; the overpotential of LaMn0·6Co0·4O3@NG at 10 mA cm−2 is 314 mV for OER, smaller than that of LaMnO3@NG and LaCoO3@NG, supposing the superior electrochemical activity of composite catalyst with Co substitution in OER and ORR. This research offers a way in fabricating high efficient and cost-effective bifunctional electrocatalyst for Zinc-air batteries.

Sulphur- and nitrogen-codoped layered double hydroxides with expanded interlayer distance for enhanced overall water splitting

Developing highly active, durable, and non-noble electrocatalysts for water-splitting is critical for efficient renewable energy conversion. Nickel-iron layered double-hydroxide (NiFe-LDH) materials show potential in achieving good catalytic performance, however, which was restricted by the scarce active sites and poor conductivity. Herein, we report a series of NiFe-LDH-based materials of expanded interlayer spacing constructed through S/N co-doping with rich active sites, used as a high-efficient bifunctional electrocatalyst for the oxygen and hydrogen evolution reactions (OER and HER). The experimental results indicate that the intercalation/decoration on the interlayer structure of NiFe-LDH can efficiently reduce the energy barrier and accelerate reaction kinetics. Combining with the structural advantages, including the expanded lattice spacing and exposed active surface sites, the resulting S-N/NiFe-LDH anchored in nickel foam (NF) drives an alkaline electrolyzer with a cell voltage of 1.67 V at a current density of 100 mA cm−2, as well as robust stability over 100 h, which is much superior to the state-of-the-art Pt/C-RuO2 electrocatalysts.

COF-derived Co nanoparticles@N-doped carbon electrocatalysts for high performance Zn-air batteries

Precise modulation of the structure and composition of electrocatalysts is critical for promoting the kinetically sluggish process of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Covalent organic frameworks (COF) offer a novel way to create highly efficient electrocatalysts due to their tunable composition, structure and surface area. Herein, we report a high-efficiency bifunctional electrocatalyst comprising Co nanoparticles embedded within N-doped carbons (Co@NCs) for Zn-air batteries (ZABs). The Co@NC is yielded via the coordination of a triazine COF with Co-containing precursors and subsequent calcination under inert atmosphere. The as-prepared Co@NC exhibits remarkable ORR/OER performance and great potential in rechargeable ZABs. The liquid ZAB constructed with Co@NC provides both high specific capacity and power density. Remarkably, the ZAB exhibits a voltage gap of 0.8 V during discharge and charge cycles and high stability for 220 h compared to the Pt/C-assembled battery. This strategy for regulating electrocatalytic activities of COF-derived carbon materials could be expanded for creating various carbon catalysts.

High-efficiency oxygen electrocatalyst for Zn-air batteries on CoMn alloy encapsulated in N-doped carbon architectures

A low-cost efficient electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is urgently required for the commercialization of Zn-air batteries. Herein, CoMn nanoalloys encapsulated in nitrogen-doped hollow carbon architectures (CoMn@NHC) as dual electrocatalysts for Zn-air batteries were developed successfully. The obtained CoMn@NHC nanohybrid expresses excellent electrocatalytic performances for ORR (E1/2 = 0.87 V) and OER (Ei=10 = 1.51 V). More encouragingly, a homemade aqueous Zn-air battery using CoMn@NHC catalyst delivers a larger peak power density of 92.3 mW cm−2 and excellent stability of nearly 300 h, outperforming the commercial Pt/C + RuO2. The remarkable electrocatalytic performances are owing to the unique microstructure and the synergistic effect between CoMn alloy and N-doped carbon substrate. This study opens a new way for designing high-efficient bifunctional electrocatalysts for application in renewable energy facilities.

Spontaneous Internal Electric Field in Heterojunction Boosts Bifunctional Oxygen Electrocatalysts for Zinc-Air Batteries: Theory, Experiment, and Application.

Heterojunctions are a promising class of materials for high-efficiency bifunctional oxygen electrocatalysts in both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the conventional theories fail to explain why many catalysts behave differently in ORR and OER, despite a reversible path (* O2 ⇋* OOH⇋* O⇋* OH). This study proposes the electron-/hole-rich catalytic center theory (e/h-CCT) to supplement the existing theories, it suggests that the Fermi level of catalysts determines the direction of electron transfer, which affects the direction of the oxidation/reduction reaction, and the density of states (DOS) near the Fermi level determines the accessibility for injecting electrons and holes. Additionally, heterojunctions with different Fermi levels form electron-/hole-rich catalytic centers near the Fermi levels to promote ORR/OER, respectively. To verify the universality of the e/h-CCT theory,this study reveals the randomly synthesized heterostructural Fe3 N-FeN0.0324 (Fex N@PC with DFT calculations and electrochemical tests. The results show that the heterostructural F3 N-FeN0.0324 facilitates the catalytic activities for ORR and OER simultaneously by forming an internal electron-/hole-rich interface. The rechargeable ZABs with Fex N@PC cathode display a high open circuit potential of 1.504 V, high power density of 223.67 mW cm-2 , high specific capacity of 766.20 mAh g-1 at 5 mA cm-2 , and excellent stability for over 300 h.

Edge atomic Fe sites decorated porous graphitic carbon as an efficient bifunctional oxygen catalyst for Zinc-air batteries

The development of advanced bifunctional oxygen electrocatalysts for oxygen reduction and evolution reactions (ORR and OER) is critical to the practical application of zinc-air batteries (ZABs). Herein, a silica-assisted method is reported to integrate numerous accessible edge Fe-Nx sites into porous graphitic carbon (named Fe-N-G) for achieving highly active and robust oxygen electrocatalysis. Silica facilitates the formation of edge Fe-Nx sites and dense graphitic domains in carbon by inhibiting iron aggregation. The purification process creates a well-developed mass transfer channel for Fe-N-G. Consequently, Fe-N-G delivers a half-wave potential of 0.859 V in ORR and an overpotential of 344 mV at 10 mA cm−2 in OER. During long-term operation, the graphitic layers protect edge Fe-Nx sites from demetallation in ORR and synergize with FeOOH species endowing Fe-N-G with enhanced OER activity. Density functional theory calculations reveal that the edge Fe-Nx site is superior to the in-plane Fe-Nx site in terms of OH* dissociation in ORR and OOH* formation in OER. The constructed ZAB based on Fe-N-G cathode shows a higher peak power density of 133 mW cm−2 and more stable cycling performance than Pt/C + RuO2 counterparts. This work provides a novel strategy to obtain high-efficiency bifunctional oxygen electrocatalysts through space mediation.

IrPd Nanoalloy-Structured Bifunctional Electrocatalyst for Efficient and pH-Universal Water Splitting.

The lack of high efficiency and pH-universal bifunctional electrocatalysts for water splitting to hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hinders the large-scale production of green hydrogen. Here, an IrPd electrocatalyst supported on ketjenblack that exhibits outstanding bifunctional performance for both HER and OER at wide pH conditions is presented. The optimized IrPd catalyst exhibits a specific activity of 4.46 and 3.98 A mgIr -1 in the overpotential of 100 and 370mV for HER and OER, respectively, in alkaline conditions. When applied to the anion exchange membrane electrolyzer, the Ir44 Pd56 /KB catalyst shows a stability of >20h at a current of 250mA cm-2 for water decomposition, indicating promising prospects for practical applications. Beyond offering an advanced electrocatalyst, this work also guides the rational design of desirable bifunctional electrocatalysts for HER and OER by regulating the microenvironments and electronic structures of metal catalytic sites for diverse catalysis.

Cobalt loaded on concave hollow carbon octadecahedron for zinc–air batteries

For the development of high-performance zinc–air batteries, it is necessary to increase the kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) as much as possible. In this work, different coordination structures of Co loaded on concave hollow carbon octadecahedron (CNQD/CoNBs) were prepared by adding g-C3N4 into the synthesis process of Co-based zeolitic imidazolate framework and adjusting the stress balance of the framework structure in the pyrolysis process. This method can greatly increase the specific surface area and the number of micropores of the material for exposing more active sites to accelerate the reaction kinetics. The prepared catalyst shows excellent bi-functional performance for OER and ORR, and it is applied in efficient rechargeable zinc–air battery to achieve high discharge power density of 210 mW/cm2 and favorable stability over long charge/discharge cycles. This research provides an effective strategy to design high-efficiency bi-functional electrocatalysts.