Enhanced electrocatalytic performance for oxygen evolution reaction via active interfaces of Co3O4arrays@FeOx/Carbon cloth heterostructure by plasma-enhanced atomic layer deposition.

Oxygen evolution reaction (OER) is a necessary procedure in various devices including water splitting and rechargeable metal-air batteries but required a higher potential to improve oxygen evolution efficiency due to its slow reaction kinetics. In order to solve this problem, a heterostructured electrocatalyst (Co3O4@FeOx/CC) is synthesized by deposition of iron oxides (FeOx) on carbon cloth (CC) via plasma-enhanced atomic layer deposition, then growth of the cobalt oxide (Co3O4) nanosheet arrays. The deposition cycle of FeOxon the CC strongly influences thein situgrowth and distribution of Co3O4nanosheets and electronic conductivity of the electrocatalyst. Owing to the high accessible and electroactive areas and improved electrical conductivity, the free-standing electrode of Co3O4@FeOx/CC with 100 deposition cycles of FeOxexhibits excellent electrocatalytic performance for OER with a low overpotential of 314.0 mV at 10 mA cm-2and a small Tafel slope of 29.2 mV dec-1in alkaline solution, which is much better than that of Co3O4/CC (448 mV), and even commercial RuO2(380 mV). This design and optimization strategy shows a promising way to synthesize ideally designed catalytic architectures for application in energy storage and conversion.

Unlocking the Interfacial Adsorption-Intercalation Pseudocapacitive Storage Limit to Enabling All-Climate, High Energy/Power Density and Durable Zn-Ion Batteries.

Sluggish storage kinetics and insufficient performance are the major challenges that restrict the transition metal dichalcogenides (TMDs) applied for zinc ion storage, especially at the extreme temperature conditions. Herein, a multiscale interface structure-integrated modulation concept was presented, to unlock the omnidirectional storage kinetics-enhanced porous VSe2-x ⋅n H2 O host. Theory research indicated that the co-modulation of H2 O intercalation and selenium vacancy enables enhancing the interfacial zinc ion capture ability and decreasing the zinc ion diffusion barrier. Moreover, an interfacial adsorption-intercalation pseudocapacitive storage mechanism was uncovered. Such cathode displayed remarkable storage performance at the wide temperature range (-40-60 °C) in aqueous and solid electrolytes. In particular, it can retain a high specific capacity of 173 mAh g-1 after 5000 cycles at 10 A g-1 , as well as a high energy density of 290 Wh kg-1 and a power density of 15.8 kW kg-1 at room temperature. Unexpectedly, a remarkably energy density of 465 Wh kg-1 and power density of 21.26 kW kg-1 at 60 °C also can be achieved, as well as 258 Wh kg-1 and 10.8 kW kg-1 at -20 °C. This work realizes a conceptual breakthrough for extending the interfacial storage limit of layered TMDs to construct all-climate high-performance Zn-ion batteries.

Converting Spent LiFePO4 Battery into Zeolitic Phosphate for Highly Efficient Heavy Metal Adsorption.

Developing efficient recycling technologies for large-scale spent batteries is the key to build a zero-waste city. Herein, a [Al8.5Fe0.5P12O48]·[C24H72N16]·[Li·4H2O]·[12H2O] (AlFePO-Li) zeolite, crystallizing in space group I4̅3m with a = 16.6778(3) Å, has been constructed via the hydrothermal treatment of spent LiFePO4 battery. Benefiting from the three-dimensional 12-member-ring channels in its structure and chemical adsorption, excellent Pb2+ removal capacity up to 723.8 mg g-1 has been achieved. Detailed adsorption mechanism study revealed that the cation exchange capacity is significantly contributed by ion exchange of the protonated organic amine cations in the zeolite channel and the protons from the framework dangling phosphate group. This work demonstrates a novel method of reutilizing spent LIBs to construct zeolite for heavy metal removal. It is of great importance to achieve sustainable development based on the "resource utilization" and "trash-to-treasure" strategy.

Robust SnO2-x Nanoparticle-Impregnated Carbon Nanofibers with Outstanding Electrochemical Performance for Advanced Sodium-Ion Batteries.

The sluggish sodium reaction kinetics, unstable Sn/Na2 O interface, and large volume expansion are major obstacles that impede practical applications of SnO2 -based electrodes for sodium-ion batteries (SIBs). Herein, we report the crafting of homogeneously confined oxygen-vacancy-containing SnO2-x nanoparticles with well-defined void space in porous carbon nanofibers (denoted SnO2-x /C composites) that address the issues noted above for advanced SIBs. Notably, SnO2-x /C composites can be readily exploited as the working electrode, without need for binders and conductive additives. In contrast to past work, SnO2-x /C composites-based SIBs show remarkable electrochemical performance, offering high reversible capacity, ultralong cyclic stability, and excellent rate capability. A discharge capacity of 565 mAh g-1 at 1 A g-1 is retained after 2000 cycles.

In-situ one-step construction of poly(heptazine imide)/poly(triazine imide) heterojunctions for photocatalytic hydrogen evolution.

The construction of heterojunctions is challenging, requiring atomic-level contact and interface matching. Here, we have achieved atomic-level interfacial matching by constructing poly(heptazine imide)/poly(triazine imide) crystalline carbon nitride heterojunctions in an in-situ one-step method. The content of poly(triazine imide) in heterojunctions is positively related to the proportion of lithium chloride in potassium chloride and lithium chloride mixed-salts. The optimized heterojunction achieves an apparent quantum efficiency of 48.34 % for photocatalytic hydrogen production at 420 nm, which is at a good level in polymeric carbon nitride photocatalysts. The proposed ion-thermal assisted heterojunction construction strategy contributes to the development of polymeric carbon nitride photocatalysts with high crystallization and high charge separation efficiency.

Unlocking the Design Paradigm of In-Plane Heterojunction with Built-in Bifunctional Anion Vacancy for Unexpectedly Fast Sodium Storage.

Transition metal chalcogenide (TMD) electrodes in sodium-ion batteries exhibit intrinsic shortcomings such as sluggish reaction kinetics, unstable conversion thermodynamics, and substantial volumetric strain effects, which lead to electrochemical failure. This report unlocks a design paradigm of VSe2- x /C in-plane heterojunction with built-in anion vacancy, achieved through an in situ functionalization and self-limited growth approach. Theoretical and experimental investigations reveal the bifunctional role of the Se vacancy in enhancing the ion diffusion kinetics and the structural thermodynamics of Nax VSe2 active phases. Moreover, this in-plane heterostructure facilitates complete face contact between the two components and tight interfacial conductive contact between the conversion phases, resulting in enhanced reaction reversibility. The VSe2- x /C heterojunction electrode exhibits remarkable sodium-ion storage performance, retaining specific capacities of 448.7 and 424.9 mAh g-1 after 1000 cycles at current densities of 5 and 10 A g-1 , respectively. Moreover, it exhibits a high specific capacity of 353.1 mAh g-1 even under the demanding condition of 100 A g-1 , surpassing most previous achievements. The proposed strategy can be extended to other V5 S8- x and V2 O5- x -based heterojunctions, marking a conceptual breakthrough in advanced electrode design for constructing high-performance sodium-ion batteries.

Polypyrrole pre-intercalation engineering-induced NH4+ removal in tunnel ammonium vanadate toward high-performance zinc ion batteries.

Ammonium vanadate with stable bi-layered structure and superior mass-specific capacity have emerged as competitive cathode materials for aqueous rechargeable zinc-ion batteries (AZIBs). Nevertheless, fragile NH…O bonds and too strong electrostatic interaction by virtue of excessive NH4+ will lead to sluggish Zn2+ ion mobility, further largely affects the electro-chemical performance of ammonium vanadate in AZIBs. The present work incorporates polypyrrole (PPy) to partially replace NH4+ in NH4V4O10 (NVO), resulting in the significantly enlarged interlayers (from 10.1 to 11.9 Å), remarkable electronic conductivity, increased oxygen vacancies and reinforced layered structure. The partial removal of NH4+ will alleviate the irreversible deammoniation to protect the laminate structures from collapse during ion insertion/extraction. The expanded interlayer spacing and the increased oxygen vacancies by the virtue of the introduction of polypyrrole improve the ionic diffusion, enabling exceptional rate performance of NH4V4O10. As expected, the resulting polypyrrole intercalated ammonium vanadate (NVOY) presents a superior discharge capacity of 431.9 mAh g-1 at 0.5 A g-1 and remarkable cycling stability of 219.1 mAh g-1 at 20 A g-1 with 78 % capacity retention after 1500 cycles. The in-situ electrochemical impedance spectroscopy (EIS), in-situ X-ray diffraction (XRD), ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ high resolution transmission electron microscopy (HR-TEM) analysis investigate a highly reversible intercalation Zn-storage mechanism, and the enhanced the redox kinetics are related to the combined effect of interlayer regulation, high electronic conductivity and oxygen defect engineering by partial substitution NH4+ of PPy incorporation.

Correction: Long cyclic stability of acidic aqueous zinc-ion batteries achieved by atomic layer deposition: the effect of the induced orientation growth of the Zn anode.

Correction for 'Long cyclic stability of acidic aqueous zinc-ion batteries achieved by atomic layer deposition: the effect of the induced orientation growth of the Zn anode' by Zhisen Zeng et al., Nanoscale, 2021, 13, 12223-12232, https://doi.org/10.1039/d1nr02620h.

3D Artificial Array Interface Engineering Enabling Dendrite-Free Stable Zn Metal Anode.

The ripple effect induced by uncontrollable Zn deposition is considered as the Achilles heel for developing high-performance aqueous Zn-ion batteries. For this problem, this work reports a design concept of 3D artificial array interface engineering to achieve volume stress elimination, preferred orientation growth and dendrite-free stable Zn metal anode. The mechanism of MXene array interface on modulating the growth kinetics and deposition behavior of Zn atoms were firstly disclosed on the multi-scale level, including the in-situ optical microscopy and transient simulation at the mesoscopic scale, in-situ Raman spectroscopy and in-situ X-ray diffraction at the microscopic scale, as well as density functional theory calculation at the atomic scale. As indicated by the electrochemical performance tests, such engineered electrode exhibits the comprehensive enhancements not only in the resistance of corrosion and hydrogen evolution, but also the rate capability and cyclic stability. High-rate performance (20 mA cm-2) and durable cycle lifespan (1350 h at 0.5 mA cm-2, 1500 h at 1 mA cm-2 and 800 h at 5 mA cm-2) can be realized. Moreover, the improvement of rate capability (214.1 mAh g-1 obtained at 10 A g-1) and cyclic stability also can be demonstrated in the case of 3D MXene array@Zn/VO2 battery. Beyond the previous 2D closed interface engineering, this research offers a unique 3D open array interface engineering to stabilize Zn metal anode, the controllable Zn deposition mechanism revealed is also expected to deepen the fundamental of rechargeable batteries including but not limited to aqueous Zn metal batteries.

Hydroxylamine mediated Fenton-like interfacial reaction dynamics on sea urchin-like catalyst derived from spent LiFePO4 battery.

Herein, we converted spent LiFePO4 battery to the sea urchin-like material (SULM) with a highly efficient and environment-friendly method, which can contribute to building a zero-waste city. With SULM as a Fenton-like catalyst, a highly-efficient degradation process was realized for organic pollutants with interface and solution synergistic effect. In our SULM+NH2OH+H2O2 Fenton-like system, NH2OH can effectively promote the interface iron (Fe(Ⅲ)/Fe(Ⅱ)) and solution iron (Fe(Ⅲ)/Fe(Ⅱ)) redox cycle, thus promoting the generation of reactive oxygen species (ROS). However, the ROS generation process and organic pollutants degradation pathway with the presence of NH2OH remains a puzzle. Here the detailed ROS generation mechanism and pollutants degradation pathway have been illustrated carefully based on experimental exploration and characterization. Therein, hydroxyl radicals (·OH) and singlet oxygen (1O2) are the main ROS for oxidizing and degrading organic pollutants. Notably, 1O2 can be converted from superoxide radicals (·O2) in SULM+NH2OH+H2O2 system. This study not only demonstrates the strategy of "trash-to-treasure" and "waste-to-control-waste" to simultaneously reduce the hazardous release from industrial solid waste and organic wastewater, it also provides new mechanistic insights for NH2OH mediated Fenton-like redox system.

Breaking the Limitation of Elevated Coulomb Interaction in Crystalline Carbon Nitride for Visible and Near-Infrared Light Photoactivity.

Most near-infrared (NIR) light-responsive photocatalysts inevitably suffer from low charge separation due to the elevated Coulomb interaction between electrons and holes. Here, an n-type doping strategy of alkaline earth metal ions is proposed in crystalline K+ implanted polymeric carbon nitride (KCN) for visible and NIR photoactivity. The n-type doping significantly increases the electron densities and activates the n→π* electron transitions, producing NIR light absorption. In addition, the more localized valence band (VB) and the regulation of carrier effective mass and band decomposed charge density, as well as the improved conductivity by 1-2 orders of magnitude facilitate the charge transfer and separation. The proposed n-type doping strategy improves the carrier mobility and conductivity, activates the n→π* electron transitions for NIR light absorption, and breaks the limitation of poor charge separation caused by the elevated Coulomb interaction.

A Multifunctional Anti-Proton Electrolyte for High-Rate and Super-Stable Aqueous Zn-Vanadium Oxide Battery.

Large volumetric expansion of cathode hosts and sluggish transport kinetics in the cathode-electrolyte interface, as well as dendrite growth and hydrogen evolution at Zn anode side are considered as the system problems that cause the electrochemical failure of aqueous Zn-vanadium oxide battery. In this work, a multifunctional anti-proton electrolyte was proposed to synchronously solve all those issues. Theoretical and experimental studies confirm that PEG 400 additive can regulate the Zn2+ solvation structure and inhibit the ionization of free water molecules of the electrolyte. Then, smaller lattice expansion of vanadium oxide hosts and less associated by-product formation can be realized by using such electrolyte. Besides, such electrolyte is also beneficial to guide the uniform Zn deposition and suppress the side reaction of hydrogen evolution. Owing to the integrated synergetic modification, a high-rate and ultrastable aqueous Zn-V2O3/C battery can be constructed, which can remain a specific capacity of 222.8 mAh g-1 after 6000 cycles at 5 A g-1, and 121.8 mAh g-1 even after 18,000 cycles at 20 A g-1, respectively. Such "all-in-one" solution based on the electrolyte design provides a new strategy for developing high-performance aqueous Zn-ion battery.

An aqueous polyethylene oxide-based solid-state electrolyte with high voltage stability for dendrite-free lithium deposition via a self-healing electrostatic shield.

Lithium metal batteries (LMBs) have attracted extensive attention for their ultrahigh energy density. However, the uncontrollable growth of Li-dendrites results in poor cyclability and potential safety risks, thus preventing their practical application. Herein, a flexible and cost-effective aqueous polyethylene oxide (PEO)-based solid-state electrolyte is prepared, which enables uniform and dendrite-free Li deposition by introducing Cs+ with an electrostatic shielding mechanism at high current densities. The self-assembly of PEO and bacterial cellulose by hydrogen bonding reduces the crystallinity of PEO and increases uniformly the distribution of lithium ions. With excellent flexibility and thermal stability, such a 3D polymer solid-state electrolyte exhibits an enhanced electrochemical stability window of 5.8 V versus Li/Li+ potential and a high ionic conductivity of 1.28 × 10-4 S cm-1 at 60 °C. The Li|BC-PEO-Cs+|Li symmetric cells operate stably for more than 1000 h. Furthermore, Li|BC-PEO-Cs+|LiFePO4 (LFP) cells show remarkable enhancement in capacity (163.4 mA h g-1 at 0.1 C), cycling stability (with a capacity retention of 96% after 500 cycles at 1 C) and high functionality and safety (withstanding folding and cutting) in practical applications.

Donor Bandgap Engineering without Sacrificing the Reduction Ability of Photogenerated Electrons in Crystalline Carbon Nitride.

Crystalline carbon nitride (CCN) with a light response up to 700 nm has been seldom reported but is significant for the artificial photocatalysis. In this study, it is proposed that, unlike acceptors, introducing donors can effectively narrow the bandgap without sacrificing the reduction ability of photogenerated electrons, which is more advantageous to photocatalytic reduction reactions. Hence, a series of heptazine-based K+ -implanted CCN (KCN) with a narrow bandgap (2.87-1.86 eV) are constructed by copolymerization of pyrimidine donors. The optimized photocatalysts can extend the light response to 700 nm and account for approximately 122- and 33-fold enhancements in H2 production (λ>500 nm) in comparison to CN and KCN, respectively. The apparent quantum efficiency (AQE) can reach 8.2 % at 500 nm and is comparable to the top-level CN- and CCN- based materials. Its photoactive wavelength has significant advantages over previously reported CCN-based photocatalysts. This method offers a universal donor bandgap engineering strategy towards photocatalytic reduction reactions.

Long cyclic stability of acidic aqueous zinc-ion batteries achieved by atomic layer deposition: the effect of the induced orientation growth of the Zn anode.

Aqueous Zn-ion batteries with economical ZnSO4 solution as the electrolyte suffer from a tremendous tendency of dendrite formation under mildly acidic conditions; moreover, utilization of Zn(CF3SO3)2 delivers superior performance, but is expensive. Herein, we optimize the ZnSO4 electrolyte by inducing 50 µL of 10 M sulfuric acid in 10 mL electrolyte, which can achieve long cycle life (1000 h at 0.1 mA cm-2, 300 h at 1 mA cm-2 and 250 h at 10 mA cm-2) when the Zn foil is protected by three metallic oxides deposited by atomic layer deposition (ALD). The nucleation behaviour of the (002) facet has proved to play a critical role in the reversible lifespan. The Al2O3 layer would restrict the stripping procedure, leading to the highest overpotential, while the TiO2 layer and Fe2O3 layer tended to strip all orientations but the (002) facet. Al2O3@Zn demonstrated a preference for a compact hillock-like (101) orientation texture in the deposition procedure, while TiO2@Zn and Fe2O3@Zn were favourable to obtain a smooth terrace texture. Additionally, symmetric cells with Fe2O3@Zn expressed the lowest overpotential (31.64 mV) and minimal voltage hysteresis (23.6 mV) at 1 mA cm-2. A Zn-MnO2 battery with Fe2O3@Zn also displayed superior capacity, which could reach 280 mA h g-1 at a current density of 1 A g-1. The diffusion coefficient of Zn2+ discloses that among the three ALD layers, full cells with Fe2O3@Zn are the most favourable for diffusion of Zn2+ in acidic electrolyte.

Unveiling the reaction mechanism of an Sb2S3-Co9S8/NC anode for high-performance lithium-ion batteries.

Metal sulfides are promising lithium-ion battery anode materials with high specific capacities, but there has been little in-depth discussion on the reaction mechanism of metal sulfides. In this study, a robust bimetallic sulfide heterogeneous material (Sb2S3-Co9S8/NC) based on a metal-organic framework was designed. The combination of in situ X-ray diffraction and ex situ transmission electron microscopy revealed the phase evolution behavior during the first cycle. During the lithiation process, Sb2S3 undergoes lithium insertion, conversion and alloying reactions to form crystalline Li2S, Li3Sb and metallic Sb. Co9S8 undergoes lithium insertion and transformation to form metallic Co and Li2S. Lithium ions are extracted from the nanocrystalline phase and transformed into the original Sb2S3 and Co9S8 phases. The Sb2S3-Co9S8/NC anode exhibits excellent cycle stability (616 mA h g-1 at 2 A g-1 after 900 cycles) and fast lithium ion transfer kinetics. These results demonstrate the lithiation/delithiation mechanism of the Sb2S3-based anode and provide a new path for the development of high-performance LIB anodes based on bimetallic sulfides.

Carbon nanotubes coupled with layered graphite to support SnTe nanodots as high-rate and ultra-stable lithium-ion battery anodes.

SnTe exhibits a layered crystal structure, which enables fast Li-ion diffusion and easy storage, and is considered to be a promising candidate for an advanced anode material. However, its applications are hindered by the large volume variation caused by intercalation/deintercalation during the electrochemical reaction processes. Herein, topological insulator SnTe and carbon nanotubes (CNTs) supported on a graphite (G) carbon framework (SnTe-CNT-G) were prepared as a new, active and robust anode material for high-rate lithium-ion batteries by a scalable ball-milling method. Remarkably, the SnTe-CNT-G composite used as a lithium-ion battery anode offered an excellent reversible capacity of 840 mA h g-1 at 200 mA g-1 after 100 cycles and high initial coulombic efficiencies of 76.0%, and achieved a long-term cycling stability of 669 mA h g-1 at 2 A g-1 after 1400 cycles. The superior electrochemical performance of SnTe-CNT-G is attributed to the stable design of its electrode structure and interesting topological transition of SnTe, combined with multistep conversion and alloying processes. Furthermore, in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy were employed to study the reaction mechanism. The results presented here provide new insights to design and reveal the reaction mechanisms of transition metal telluride materials in various energy-storage materials.

ZIF-derived "senbei"-like Co9S8/CeO2/Co heterostructural nitrogen-doped carbon nanosheets as bifunctional oxygen electrocatalysts for Zn-air batteries.

The rational design and construction of the efficient and robust non-noble metal bifunctional oxygen electrocatalysts is of critical significance due to the attention given to reversible metal-air batteries. In this paper, we report novel two-dimensional "senbei"-like Co9S8/CeO2/Co-NC nitrogen-doped carbon nanosheets (Co9S8/CeO2/Co-NC) derived from a unique 2D Co/Ce bimetallic ZIF. The phase transition from 3D spherical Co-ZIF to 2D Co/Ce-ZIF was achieved through the introduction of Ce ions. Profiting from the successful construction of the unique Co9S8/CeO2 heterostructure and the synergetic effect of two components, the as-prepared Co9S8/CeO2/Co-NC exhibited excellent electro-performance in both the oxygen evolution reaction (Ej=10 = 1.60 V) and oxygen reduction reaction (E1/2 = 0.875 V). Furthermore, when used as a bifunctional air electrode for Zn-air batteries, Co9S8/CeO2/Co-NC reached a high peak power density of ≈164.24 mW cm-2 at a high current density of ≈351 mA cm-2 and displayed an outstanding cycling stability of more than 668 h at 5 mA cm-2. This research provides new guidelines for preparing hybrid materials from cobalt-based sulfide species and CeO2 for electrocatalysis and energy storage or other fields.

High-efficiency core-shell magnetic heavy-metal absorbents derived from spent-LiFePO4 Battery.

Search for simple and efficient recycling methods to utilize spent lithium-ion batteries is crucial for achieving sustainable resource development and reducing the hazardous materials released from the spent batteries. Herein, we have developed a new strategy to utilize the spent LiFePO4 batteries by utilizing the cathode plate as raw material to synthesize mesoporous core-shell adsorbent Mm@SiO2 (Mm denoted as the magnetic material) through a simple alkaline leaching process. The as-converted material exhibits excellent adsorption capacity when it has been used to remove heavy metal ions in heavy metal polluted water. The adsorption capacities for Cu2+, Cd2+, and Mn2+ have been achieved up to 71.23, 80.31 and 68.73 mg g-1, respectively. The detailed adsorption mechanism has been elucidated with comprehensive characterization techniques, including TEM, XPS, NEXAS, and EXAFS, the edge shared [Cu2O8] bipyramids can be fit against the EXAFS data to represent the atomic-scale local structure after Mm@SiO2 adsorbs Cu2+. The present work demonstrates a novel routine to reutilize the spent lithium batteries, which is of great importance to achieve sustainable development based on the "waste-to-treasure" and "waste-to-control-waste" strategy for simultaneously reducing the hazardous release from industrial solid waste and heavy metal polluted water.

Co/CoP Nanoparticles Encapsulated Within N, P-Doped Carbon Nanotubes on Nanoporous Metal-Organic Framework Nanosheets for Oxygen Reduction and Oxygen Evolution Reactions.

Herein, Co/CoP nanoparticles encapsulated with N, P-doped carbon nanotubes derived from the atomic layer deposited hexagonal metal-organic frameworks (MOFs) are obtained by calcinations and subsequent phosphating and are employed as electrocatalyst. The electrocatalytic performance evaluations show that the as-prepared electrocatalyst exhibits an overpotential of 342 mV at current density of 10 mA cm-2 and the Tafel slope of 74 mV dec-1 for oxygen evolution reaction (OER), which is superior to the most advanced ruthenium oxide electrocatalyst. The electrocatalyst also shows better stability than the benchmark RuO2. After 9 h, the current density is only decreased by 10%, which is far less than the loss of RuO2. Moreover, its onset potential for oxygen reduction reaction (ORR) is 0.93 V and follows the ideal 4-electron approach. After the stability test, the current density of the electrocatalyst retains 94% of the initial value, which is better than Pt/C. The above results indicate that the electrocatalyst has bifunctional activity and excellent stability both for OER and ORR. It is believed that this strategy provides guidance for the synthesis of cobalt phosphide/carbon-based electrocatalysts.