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Showing papers on "Oxide published in 2020"


Journal ArticleDOI
TL;DR: Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties as discussed by the authors, and a review focusing on the functional modification of GAs is presented in this paper.
Abstract: Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties. This review focuses on the functional modification of graphene and graphene oxide. First, the basic structure, preparation methods and properties of graphene and graphene oxide are briefly described. Subsequently, the methods for the reduction of graphene oxide are introduced. Next, the functionalization of graphene and graphene oxide is mainly divided into covalent binding modification, non-covalent binding modification and elemental doping. Then, the properties and application prospects of the modified products are summarized. Finally, the current challenges and future research directions are presented in terms of surface functional modification for graphene and graphene oxide.

503 citations


Journal ArticleDOI
03 Jan 2020
TL;DR: The metal oxides have been of great importance to the development of energy conversion and storage technologies including heterojunction solar cells, Li-ion batteries, and electrocatalysts/photocatalys.
Abstract: Metal oxides have been of great importance to the development of energy conversion and storage technologies including heterojunction solar cells, Li-ion batteries, and electrocatalysts/photocatalys...

408 citations


Journal ArticleDOI
27 Jan 2020-Nature
TL;DR: Flash Joule heating of inexpensive carbon sources is used to produce gram-scale quantities of high-quality graphene in under a second, without the need for a furnace, solvents or reactive gases.
Abstract: Most bulk-scale graphene is produced by a top-down approach, exfoliating graphite, which often requires large amounts of solvent with high-energy mixing, shearing, sonication or electrochemical treatment1–3. Although chemical oxidation of graphite to graphene oxide promotes exfoliation, it requires harsh oxidants and leaves the graphene with a defective perforated structure after the subsequent reduction step3,4. Bottom-up synthesis of high-quality graphene is often restricted to ultrasmall amounts if performed by chemical vapour deposition or advanced synthetic organic methods, or it provides a defect-ridden structure if carried out in bulk solution4–6. Here we show that flash Joule heating of inexpensive carbon sources—such as coal, petroleum coke, biochar, carbon black, discarded food, rubber tyres and mixed plastic waste—can afford gram-scale quantities of graphene in less than one second. The product, named flash graphene (FG) after the process used to produce it, shows turbostratic arrangement (that is, little order) between the stacked graphene layers. FG synthesis uses no furnace and no solvents or reactive gases. Yields depend on the carbon content of the source; when using a high-carbon source, such as carbon black, anthracitic coal or calcined coke, yields can range from 80 to 90 per cent with carbon purity greater than 99 per cent. No purification steps are necessary. Raman spectroscopy analysis shows a low-intensity or absent D band for FG, indicating that FG has among the lowest defect concentrations reported so far for graphene, and confirms the turbostratic stacking of FG, which is clearly distinguished from turbostratic graphite. The disordered orientation of FG layers facilitates its rapid exfoliation upon mixing during composite formation. The electric energy cost for FG synthesis is only about 7.2 kilojoules per gram, which could render FG suitable for use in bulk composites of plastic, metals, plywood, concrete and other building materials. Flash Joule heating of inexpensive carbon sources is used to produce gram-scale quantities of high-quality graphene in under a second, without the need for a furnace, solvents or reactive gases.

373 citations


Journal ArticleDOI
TL;DR: In this review, oxide supported single-atom catalysts are discussed about their synthetic procedures, characterizations, and reaction mechanism in thermocatalysis, such as water-gas shift reaction, selective oxidation/hydrogenation, and coupling reactions.
Abstract: Metal atoms dispersed on the oxide supports constitute a large category of single-atom catalysts. In this review, oxide supported single-atom catalysts are discussed about their synthetic procedures, characterizations, and reaction mechanism in thermocatalysis, such as water-gas shift reaction, selective oxidation/hydrogenation, and coupling reactions. Some typical oxide materials, including ferric oxide, cerium oxide, titanium dioxide, aluminum oxide, and so on, are intentionally mentioned for the unique roles as supports in anchoring metal atoms and taking part in the catalytic reactions. The interactions between metal atoms and oxide supports are summarized to give a picture on how to stabilize the atomic metal centers, and rationally tune the geometric structures and electronic states of single atoms. Furthermore, several directions in fabricating single-atom catalysts with improved performance are proposed on the basis of state-of-the-art understanding in metal-oxide interactions.

352 citations


Journal ArticleDOI
TL;DR: It is reported that catalysts with nanocavities can confine carbon intermediates formed in situ, which in turn covers the local catalyst surface and thereby stabilizes Cu+ species, which leads to the marked C2+ selectivity at large conversion rate.
Abstract: Selective and efficient catalytic conversion of carbon dioxide (CO2) into value-added fuels and feedstocks provides an ideal avenue to high-density renewable energy storage. An impediment to enabling deep CO2 reduction to oxygenates and hydrocarbons (e.g., C2+ compounds) is the difficulty of coupling carbon-carbon bonds efficiently. Copper in the +1 oxidation state has been thought to be active for catalyzing C2+ formation, whereas it is prone to being reduced to Cu0 at cathodic potentials. Here we report that catalysts with nanocavities can confine carbon intermediates formed in situ, which in turn covers the local catalyst surface and thereby stabilizes Cu+ species. Experimental measurements on multihollow cuprous oxide catalyst exhibit a C2+ Faradaic efficiency of 75.2 ± 2.7% at a C2+ partial current density of 267 ± 13 mA cm-2 and a large C2+-to-C1 ratio of ∼7.2. Operando Raman spectra, in conjunction with X-ray absorption studies, confirm that Cu+ species in the as-designed catalyst are well retained during CO2 reduction, which leads to the marked C2+ selectivity at a large conversion rate.

289 citations


Journal ArticleDOI
TL;DR: In this article, the most important categories of recent applications based on reduced graphene oxide, with the emphasis on the relationship between the enhanced composite/device functionality and methods used to synthesize, to functionalize and/or to process and to structure reduced graphite oxide.
Abstract: Reduced graphene oxide has similar mechanical, optoelectronic or conductive properties to pristine graphene because it possesses a heterogeneous structure comprised of a graphene-like basal plane that is additionally decorated with structural defects and populated with areas containing oxidized chemical groups. The graphene-like properties make reduced graphene oxide a highly desirable material to be used in a plethora of sensorial, biological, environmental or catalytic applications as well as optoelectronic and storage devices. To further advance the development of the existent technologies and to design novel and better applications based on reduced graphene oxide, it is first necessary to understand which synthetic routes and processing strategies are suitable to significantly boost specific properties of this material alone or as a component in various composites. Therefore, in this work, we review the most important categories of recent applications based on reduced graphene oxide, with the emphasis on the relationship between the enhanced composite/device functionality and methods used to synthesize, to functionalize and/or to process and to structure reduced graphene oxide.

253 citations


Journal ArticleDOI
TL;DR: In this article, an active and selective catalyst with an active interface between Au-Pd alloy nanoparticles (NPs) and cobalt oxide supports via calcination of a composite of NPs encapsulated in metal-organic frameworks (MOFs).
Abstract: The selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is an important biomass conversion reaction. However, the multiple intermediates of the reaction make the catalyst design challenging. We engineered an active and selective catalyst with an active interface between Au-Pd alloy nanoparticles (NPs) and cobalt oxide supports via calcination of a composite of NPs encapsulated in metal-organic frameworks (MOFs). The catalyst shows an effective HMF-to-FDCA oxidation with total conversion and 95 % yield by 10 % hydrogen peroxide solution at 90 °C in one hour under atmospheric pressure. The mechanistic study shows that the engineered interface promotes the formation of hydroperoxyl radicals and dioxygen molecules, which accelerate the oxidation of reactive intermediates to FDCA. This work demonstrates the advantage of using MOF composites as a precursor to generate complex but active interfaces with a strong interaction between the metal and metal oxides.

228 citations



Journal ArticleDOI
TL;DR: The use of an "all-in-one" film as the electrode leads to excellent performance of the homemade water electrolyzer and zinc-air battery, indicating the potential of the film for practical applications.
Abstract: Developing a scalable approach to construct efficient and multifunctional electrodes for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is an urgent need for overall water splitting and zinc-air batteries. In this work, a freestanding 3D heterostructure film is synthesized from a Ni-centered metal-organic framework (MOF)/graphene oxide. During the pyrolysis process, 1D carbon nanotubes formed from the MOF link with the 2D reduced graphene oxide sheets to stitch the 3D freestanding film. The results of the experiments and theoretical calculations show that the synergistic effect of the N-doped carbon shell and Ni nanoparticles leads to an optimized film with excellent electrocatalytic activity. Low overpotentials of 95 and 260 mV are merely needed for HER and OER, respectively, to reach a current density of 10 mA cm-2 . In addition, a high half-wave potential of 0.875 V is obtained for the ORR, which is comparable to that of Pt/RuO2 and ranks among the top of non-noble-metal catalysts. The use of an "all-in-one" film as the electrode leads to excellent performance of the homemade water electrolyzer and zinc-air battery, indicating the potential of the film for practical applications.

219 citations


Journal ArticleDOI
Xiao-Tong Wang1, Ting Ouyang1, Ling Wang1, Jia-Huan Zhong1, Zhao-Qing Liu1 
TL;DR: The atomic-level insight into the new catalyst activation strategy based on Zn vacancies is adaptable for developing dual-functional Zn-contained spinel electrocatalysts and could elucidate the experimentally observed enhancement in the ORR activity of ZnXNi1-XCo2O4 oxides after the OER test.
Abstract: Herein, we highlight redox-inert Zn2+ in spinel-type oxide (ZnX Ni1-X Co2 O4 ) to synergistically optimize physical pore structure and increase the formation of active species on the catalyst surface. The presence of Zn2+ segregation has been identified experimentally and theoretically under oxygen-evolving condition, the newly formed VZn -O-Co allows more suitable binding interaction between the active center Co and the oxygenated species, resulting in superior ORR performance. Moreover, a liquid flow Zn-air battery is constituted employing the structurally optimized Zn0.4 Ni0.6 Co2 O4 nanoparticles supported on N-doped carbon nanotube (ZNCO/NCNTs) as an efficient air cathode, which presents remarkable power density (109.1 mW cm-2 ), high open circuit potential (1.48 V vs. Zn), excellent durability, and high-rate performance. This finding could elucidate the experimentally observed enhancement in the ORR activity of ZnX Ni1-X Co2 O4 oxides after the OER test.

218 citations


Journal ArticleDOI
19 Aug 2020-Joule
TL;DR: In this article, the authors characterize and mitigate electron transfer-proton transfer reactions between NiOx hole transport layers and perovskite precursors, and identify that Ni≥3+ metal cation sites in NiOx thin films act both as Bronsted proton acceptors and Lewis electron acceptors, deprotonating cationic amines and oxidizing iodide species.

Journal ArticleDOI
01 May 2020-Carbon
TL;DR: In this paper, a corrosion protection coating with an excellent barrier, and superior active anti-corrosion characteristics was constructed through a one-pot synthesis method of zeolitic imidazolate framework-8 (ZIF-8) on the graphene oxide sheets.

Journal ArticleDOI
TL;DR: Li solid-state NMR results show an increase in Li + ions occupying the more mobile A2 environment in the composite electrolytes, which contributes to the more facile Li + transport.
Abstract: Li+ -conducting oxides are considered better ceramic fillers than Li+ -insulating oxides for improving Li+ conductivity in composite polymer electrolytes owing to their ability to conduct Li+ through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li+ -insulating oxides (fluorite Gd0.1 Ce0.9 O1.95 and perovskite La0.8 Sr0.2 Ga0.8 Mg0.2 O2.55 ) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)-based polymer composite electrolytes, each with a Li+ conductivity above 10-4 S cm-1 at 30 °C. Li solid-state NMR results show an increase in Li+ ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2-site occupancy originates from the strong interaction between the O2- of Li-salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li+ transport. All-solid-state Li-metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C.

Journal ArticleDOI
TL;DR: This work proposed a new strategy for fabricating graphene-based composites with a 3D network structure as high-efficiency microwave absorbers through a two-step strategy of hydrothermal self-assembly and subsequent high-temperature calcination of graphene oxide/multi-walled carbon nanotubes composite foams.
Abstract: Graphene foams with three-dimensional (3D) network structure, high porosity, and ultralow density have been regarded as lightweight microwave absorption materials. Herein, nitrogen-doped reduced graphene oxide/multi-walled carbon nanotube composite foams were prepared through a two-step strategy of hydrothermal self-assembly and subsequent high-temperature calcination. Morphology analysis indicated that the 3D networks were composed of overlapped flaky reduced graphene oxide. In addition, the influences of nitrogen doping, calcination temperature, and filler ratios on microwave absorption of composite foams were explored. Results manifested that the microwave absorption of composite foams was remarkably improved with the calcination temperature increased. Dramatically, it was noteworthy that the composite foam obtained under 600 °C calcination (bulk density of ∼10.8 mg/cm3) with an 8 wt % mass filler ratio presented the strongest microwave absorption of -69.6 dB at 12.5 GHz and broadest absorption bandwidth achieved 4.3 GHz (13.2-17.5 GHz) at an extremely low matching thickness equal to 1.5 mm. Moreover, the microwave absorption performance could be conveniently adjusted through modifying the thicknesses, filler ratios, and calcination temperature. The excellent microwave absorption performance of as-prepared composite foams was greatly derived from a well-constructed 3D network structure, significant nitrogen doping, enhanced polarization relaxation, and improved conduction loss. This work proposed a new strategy for fabricating graphene-based composites with a 3D network structure as high-efficiency microwave absorbers.

Journal ArticleDOI
TL;DR: This work finds that at the steady stage of CO2RR, the electrodes have all been reduced to Cu0, regardless of the initial states, suggesting that the high C2+ selectivities are not associated with specific oxidation states of Cu.
Abstract: Oxide-/hydroxide-derived copper electrodes exhibit excellent selectivity toward C2+ products during the electrocatalytic CO2 reduction reaction (CO2RR). However, the origin of such enhanced selectivity remains controversial. Here, we prepared two Cu-based electrodes with mixed oxidation states, namely, HQ-Cu (containing Cu, Cu2O, CuO) and AN-Cu (containing Cu, Cu(OH)2). We extracted an ultrathin specimen from the electrodes using a focused ion beam to investigate the distribution and evolution of various Cu species by electron microscopy and electron energy loss spectroscopy. We found that at the steady stage of the CO2RR, the electrodes have all been reduced to Cu0, regardless of the initial states, suggesting that the high C2+ selectivities are not associated with specific oxidation states of Cu. We verified this conclusion by control experiments in which HQ-Cu and AN-Cu were pretreated to fully reduce oxides/hydroxides to Cu0, and the pretreated electrodes showed even higher C2+ selectivity compared with their unpretreated counterparts. We observed that the oxide/hydroxide crystals in HQ-Cu and AN-Cu were fragmented into nanosized irregular Cu grains under the applied negative potentials. Such a fragmentation process, which is the consequence of an oxidation-reduction cycle and does not occur in electropolished Cu, not only built an intricate network of grain boundaries but also exposed a variety of high-index facets. These two features greatly facilitated the C-C coupling, thus accounting for the enhanced C2+ selectivity. Our work demonstrates that the use of advanced characterization techniques enables investigating the structural and chemical states of electrodes in unprecedented detail to gain new insights into a widely studied system.

Journal ArticleDOI
TL;DR: In this paper, the phase, crystal structure, morphology, and electromagnetic (EM) and EM wave absorption properties of binary cobalt nickel oxide Co1.29Ni1.71O4 hollowed-out spheres were characterized in detail.

Journal ArticleDOI
TL;DR: In this article, the authors summarized the recent progress in the development of MOFs-derived porous carbons and metal oxide/sulfide compounds and their applications in supercapacitors.

Journal ArticleDOI
09 Sep 2020-Nature
TL;DR: It is found that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt through the H2 reduction route.
Abstract: Platinum is a much used catalyst that, in petrochemical processes, is often alloyed with other metals to improve catalytic activity, selectivity and longevity1-5. Such catalysts are usually prepared in the form of metallic nanoparticles supported on porous solids, and their production involves reducing metal precursor compounds under a H2 flow at high temperatures6. The method works well when using easily reducible late transition metals, but Pt alloy formation with rare-earth elements through the H2 reduction route is almost impossible owing to the low chemical potential of rare-earth element oxides6. Here we use as support a mesoporous zeolite that has pore walls with surface framework defects (called 'silanol nests') and show that the zeolite enables alloy formation between Pt and rare-earth elements. We find that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt. High-resolution transmission electron microscopy and hydrogen chemisorption measurements indicate that the resultant bimetallic nanoparticles supported on the mesoporous zeolite are intermetallic compounds, which we find to be stable, highly active and selective catalysts for the propane dehydrogenation reaction. When used with late transition metals, the same preparation strategy produces Pt alloy catalysts that incorporate an unusually large amount of the second metal and, in the case of the PtCo alloy, show high catalytic activity and selectivity in the preferential oxidation of carbon monoxide in H2.

Journal ArticleDOI
TL;DR: Most reported catalysts for water oxidation undergo in situ electrochemical tuning to form the active species for their oxygen evolution reaction (OER) as discussed by the authors, and in general, the in- situ electrochemistry tran...
Abstract: Most reported catalysts for water oxidation undergo in situ electrochemical tuning to form the active species for their oxygen evolution reaction (OER). In general, the in situ electrochemical tran...

Journal ArticleDOI
TL;DR: In this article, a review of the development of different metal-oxide semiconductor (MOS) based nanostructure for CO gas sensor is summarized and the main focus is on new approaches for the synthesis of CO gas sensing by various researchers to improve the sensing performance like selectivity, sensitivity, response and recovery time with different materials and catalysts used.

Journal ArticleDOI
TL;DR: In this article, the results of the synthesis and subsequent phase transformations of FeCo nanowires depending on the annealing temperature are presented, and a three-stage process of phase transformations is established, accompanied by oxidation of the structure followed by the formation of oxide phases of the spinel type Fe2CoO4 and Co3O4.

Journal ArticleDOI
TL;DR: In this paper, the authors mainly focused on nanostructured metal oxide-based efficient photocatalysts for photoelectrochemical (PEC) water splitting applications, such as titanium dioxide (TiO2), zinc oxide (ZnO), and tungsten/wolfram trioxide (WO3).

Journal ArticleDOI
TL;DR: In this article, the removal of tetracycline (TC) by novel magnetic graphene oxide/ZnO nanocomposites was explored in order to study the feasibility of MZ as an adsorbent and photocatalyst.

Journal ArticleDOI
TL;DR: A triple conducting oxide of PrNi 0.5 Co 0.
Abstract: The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical steps for both electrolysis and fuel cell operation, especially at reduced temperatures. In this study, a triple conducting oxide of PrNi0.5Co0.5O3-δ perovskite is developed as an oxygen electrode, presenting superior electrochemical performance at 400~600 °C. More importantly, the self-sustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction, as confirmed by hydrogen permeation experiment, remarkable hydration behavior and computations.

Journal ArticleDOI
TL;DR: The electrochemical oxidation of abundantly available glycerol for the production of value-added chemicals, such as formic acid, could be a promising approach to utilize glycerols more effectively a... as discussed by the authors.
Abstract: The electrochemical oxidation of abundantly available glycerol for the production of value-added chemicals, such as formic acid, could be a promising approach to utilize glycerol more effectively a...

Journal ArticleDOI
TL;DR: A review of established laser‐based methodologies of oxide nanoparticles which include pure oxidic phases, as well as unconventional structures like defective or doped oxides, non‐equilibrium compounds, metal‐oxide core–shells and other anisotropic morphologies is presented.
Abstract: Although oxide nanoparticles are ubiquitous in science and technology, a multitude of compositions, phases, structures, and doping levels exist, each one requiring a variety of conditions for their synthesis and modification. Besides, experimental procedures are frequently dominated by high temperatures or pressures and by chemical contaminants or waste. In recent years, laser synthesis of colloids emerged as a versatile approach to access a library of clean oxide nanoparticles relying on only four main strategies running at room temperature and ambient pressure: laser ablation in liquid, laser fragmentation in liquid, laser melting in liquid and laser defect-engineering in liquid. Here, established laser-based methodologies are reviewed through the presentation of a panorama of oxide nanoparticles which include pure oxidic phases, as well as unconventional structures like defective or doped oxides, non-equilibrium compounds, metal-oxide core-shells and other anisotropic morphologies. So far, these materials showed several useful properties that are discussed with special emphasis on catalytic, biomedical and optical application. Yet, given the endless number of mixed compounds accessible by the laser-assisted methodologies, there is still a lot of room to expand the library of nano-crystals and to refine the control over products as well as to improve the understanding of the whole process of nanoparticle formation. To that end, this review aims to identify the perspectives and unique opportunities of laser-based synthesis and processing of colloids for future studies of oxide nanomaterial-oriented sciences.

Journal ArticleDOI
TL;DR: In this article, the influence of Fe doped over activated carbon (AC) supported Mn-Ce oxide catalysts was investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3.

Journal ArticleDOI
TL;DR: In this article, an ingenious Co-Co3O4@NAC is prepared for this purpose by anchoring Co single atom on both Co 3O4 nanoparticle and nitrogen-doped active carbon (NAC), where synergistic interaction among Co atoms, Co 3 O4 particles and NAC plays a significant role for excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).
Abstract: Highly efficient noble-metal-free electrocatalysts are urgently explored for high energy density and safe metal-air batteries. Herein, an ingenious Co-Co3O4@NAC is prepared for this purpose by anchoring Co single atom on both Co3O4 nanoparticle and nitrogen-doped active carbon (NAC), where synergistic interaction among Co atoms, Co3O4 particles and NAC plays a significant role for excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, the primary zinc-air battery (ZAB) with the Co-Co3O4@NAC as a cathode catalyst shows a high open circuit voltage (OCV) of 1.449 V, a specific energy density of 721 mA h/g and a maximum power density of 164 mW/cm2. The rechargeable ZAB with this catalyst displays a low voltage gap of 0.773 V at 10 mA/cm2 and stable cycling performance. This work provides a novel tactic to design elaborate high-efficient and promising bifunctional catalysts with non-noble metal atom and metal oxide for metal-air batteries.

Journal ArticleDOI
TL;DR: In this article, successfully commercialized poly(ethylene oxide) (PEO)-based solid polymer batteries (SPBs) are expected to continuously play a key role in the next generation of high energy density lithium-ion batteries.
Abstract: Successfully commercialized poly(ethylene oxide) (PEO)-based solid polymer batteries (SPBs) are expected to continuously play a key role in the next generation of high-energy density lithium-ion ba...

Journal ArticleDOI
TL;DR: A bifunctional electrocatalyst (CoFeO@BP) is developed, which is able to efficiently catalyze both HER and OER, and can be transformed to CoFe phosphide under reduction potential, in-situ generating the real active catalyst for HER.
Abstract: Water electrolysis offers a promising green technology to tackle the global energy and environmental crisis, but its efficiency is greatly limited by the sluggish reaction kinetics of both the cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). In this work, by growing amorphous multi-transition-metal (cobalt and iron) oxide on two-dimensional (2D) black phosphorus (BP), we develop a bifunctional electrocatalyst (CoFeO@BP), which is able to efficiently catalyze both HER and OER. The overpotentials for the hybrid CoFeO@BP catalyst to reach a current density of 10 mA cm-2 in 1 m KOH are 88 and 266 mV for HER and OER, respectively. Based on a series of ex-situ and in situ investigations, the excellent catalytic performance of CoFeO@BP is found to result from the adaptive surface structure under reduction and oxidation potentials. CoFeO@BP can be transformed to CoFe phosphide under reduction potential, in situ generating the real active catalyst for HER.