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A surface engineering strategy to form a highly active Fe–Ni structure on the surfaces of Ni-based catalysts. The surface Fe is readily oxidized under OER conditions, compensating for the charges of Ni and increasing the activity of Ni active sites.

Two-dimensional (2D) materials have many promising applications, but their scalable production remains challenging. Herein, we develop a glue-assisted grinding exfoliation (GAGE) method in which the adhesive polymer acts as a glue to massively produce 2D materials with large lateral sizes, high quality, and high yield. Density functional theory simulation shows that the exfoliation mechanism involves the competition between the binding energy of selected polymers and the 2D materials which is larger than the exfoliation energy of the layered materials. Taking h-BN as an example, the GAGE produces 2D h-BN with an average lateral size of 2.18 μm and thickness of 3.91 nm. The method is also extended to produce various other 2D materials, including graphene, MoS2, WS2, Bi2O2Se, mica, vermiculite, and montmorillonite. Two representative applications of thus-produced 2D materials have been demonstrated, including 2D h-BN/polymer composites for insulating thermal conduction and 2D MoS2-based electrocatalysts for large-current-density hydrogen evolution, indicating the great potential of massively produced 2D materials.

2D material-based heterostructures are constructed by stacking or spicing individual 2D layers to create an interface between them, which have exotic properties. Here, a new strategy for the in situ growth of large numbers of 2D heterostructures on the centimeter-scale substrate is developed. In the method, large numbers of 2D MoS

Two-dimensional (2D) materials are promising candidates in wide applications including energy storage and conversion, sensors, flexible devices, etc. The low-cost production of 2D materials with large quantities and demanded quality is the precondition for their commercial uses. For graphene and its derivatives, relatively mature techniques have been established for their scalable preparation and industrial applications. Whereas the mass production of 2D materials beyond graphene is still in its early age and it lacks a summary on this topic. This review systematically describes the state-of-the-art approaches for high-yield preparation of 2D materials beyond graphene, including “top-down” exfoliation and “bottom-up” synthetic approaches. In particular, each method is discussed from the perspectives of its principle, optimization attempts, characteristics of the obtained 2D materials, and its scalability potential. The applications that require massively-produced 2D materials are highlighted, including electrocatalysis, batteries, supercapacitors, mechanical and chemical sensors, as well as electromagnetic interference shielding and microwave absorption devices. Finally, we propose the challenges and opportunities for scalable preparation and commercial applications of 2D materials.

Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo

The use of highly-active and robust catalysts is crucial for producing green hydrogen by water electrolysis as we strive to achieve global carbon neutrality. Noble metals like platinum are currently used catalysts in industry for the hydrogen evolution, but suffer from scarcity, high price and unsatisfied performance and stability at large current density, restrict their large-scale implementations. Here we report the synthesis of a type of monolith catalyst consisting of a metal disulfide (e.g., tantalum sulfides) vertically bonded to a conductive substrate of the same metal tantalum by strong covalent bonds. These features give the monolith catalyst a mechanically-robust and electrically near-zero-resistance interface, leading to an excellent hydrogen evolution performance including rapid charge transfer and excellent durability, together with a low overpotential of 398 mV to achieve a current density of 2,000 mA cm−2 as required by industry. The monolith catalyst has a negligible performance decay after 200 h operation at large current densities. In light of its robust and metallic interface and the various choices of metals giving the same structure, such monolith materials would have broad uses besides catalysis., Water electrolysis is a promising hydrogen production technique but is restricted from large-scale application due to poor performance and high cost. Here, the authors report a mechanically stable monolith electrocatalyst that achieves superior hydrogen evolution at large current densities.

Metallic transition metal dichalcogenides, such as tantalum disulfide (TaS2), have recently emerged as promising electrocatalysts for the hydrogen evolution reaction. This work reports an effective...

Electrochemical energy conversion between electricity and chemicals through electrocatalysis is a promising strategy for the development of clean and sustainable energy sources. This is because efficient electrocatalysts can greatly reduce energy loss during the conversion process. However, poor catalytic performances and a shortage in catalyst material resources have greatly restricted the widespread applications of electrocatalysts in these energy conversion processes. To address this issue, earth-abundant two-dimensional (2D) materials with large specific surface areas and easily tunable electronic structures have emerged in recent years as promising high-performance electrocatalysts in various reactions, and because of this, this review will comprehensively discuss the engineering of these novel 2D material-based electrocatalysts and their associated heterostructures. In this review, the fundamental principles of electrocatalysis and important electrocatalytic reactions are introduced. Following this, the unique advantages of 2D material-based electrocatalysts are discussed and catalytic performance enhancement strategies are presented, including the tuning of electronic structures through various methods such as heteroatom doping, defect engineering, strain engineering, phase conversion and ion intercalation, as well as the construction of heterostructures based on 2D materials to capitalize on individual advantages. Finally, key challenges and opportunities for the future development of these electrocatalysts in practical energy conversion applications are presented.

The high-throughput scalable production of cheap, efficient and durable electrocatalysts that work well at high current densities demanded by industry is a great challenge for the large-scale implementation of electrochemical technologies. Here we report the production of a two-dimensional molybdenum disulfide-based ink-type electrocatalyst by a scalable exfoliation technique followed by a thermal treatment. The catalyst delivers a high current density of 1000 mA cm−2 at an overpotential of 412 mV for the hydrogen evolution. Using the same method, we produce a cheap mineral-based catalyst possessing excellent performance for high-current-density hydrogen evolution. Noteworthy, production rate of this catalyst is one to two orders of magnitude higher than those previously reported, and price of the mineral is five orders of magnitude lower than commercial Pt electrocatalysts. These advantages indicate the huge potentials of this method and of mineral-based cheap and abundant natural resources as catalysts in the electrochemical industry., The large-scale implementation of electrochemical technologies will require the high-throughput production of high-performance, inexpensive catalysts. Here, authors demonstrate earth abundant molybdenite as raw materials to produce efficient MoS2 catalysts for high current density H2 evolution.

Nickel–iron (Ni–Fe) compounds have received ever-increasing interest because of their high performance for the oxygen evolution reaction (OER). However, the structure and composition of the active phase of Ni–Fe compounds are not yet understood. Rational design of Ni–Fe compounds with proper composition and exposed active sites is highly desirable to further improve their performance. Here we reported the synthesis of different Ni–Fe compounds by incorporating Fe into the Ni(OH)2 lattice with controlled concentrations and obtained several products including Ni–Fe layered double hydroxides (LDHs) with different amounts of Fe and NiFe2O4. In addition, β-Ni(OH)2 without Fe and α-Fe2O3 without Ni have also been synthesized for comparison. Among these four Ni/Fe based compounds, we found that the two-dimensional (2D) Ni0.8Fe0.2-LDH nanosheets with a hexagonal shape manifest a highest OER activity with a lowest overpotential of 235 mV at 10 mA cm−2, a smallest Tafel slope of 41 mV dec−1 and excellent stability over 24 h. In situ Raman, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy show that the enhanced activity of Ni0.8Fe0.2-LDH is due to the increased oxidation state of Ni from Ni2+ to Ni3+. Our findings demonstrate that the composition of Ni–Fe compounds influences the oxidizing ability of Ni and consequently their catalytic performance. We also reveal a strong correlation between the structure and oxidizing power of the Ni in Ni–Fe compounds and their OER activity, indicating that the well-engineered structure and Ni-site electronics are the primary origins of their OER activity. This work not only provides a promising guideline for the design and synthesis of Ni/Fe based compounds, but also highlights the crucial role of each component in enhancing the activity of these electrocatalysts.

Uniform nest-like structures with high surface areas and unique pore sizes were prepared by self-assembly of the oxidized single-walled carbon nanotubes (SWCNT). After doping with cobalt and nitrogen, the assembly exhibited much higher electrocatalytic activity for the oxygen reduction reaction than the commercial Pt/C catalyst. Benefited from effective exposing the active sites and sufficient diffusion pathways of O2 for fast reaction kinetic, when used as the air electrode catalysts for a Zn-air battery, the power density constructed by the assembly reached as high as 248 mW cm−2 under the high current density of 330 mA cm−2, superior to that of Pt/C air-cathode (195 mW cm−2) and other non-precious metal catalysts ever reported.

This work aims to obtain a fundamental understanding of active sites near stone-wales (SW) defects rich nitrogen-doped graphene (DG) with specific coordination of carbon atom rings. It reveals that the SW rich defects (e.g., pentagon (5), pentagon—octagon—pentagon (i.e. 585), or pentagon-heptagon-heptagon-pentagon (5775) rings, appears correspondingly with carbon rings that brought active sites during catalytic reactions. Moreover, we anchored dual isolated metallic atoms (Ni/Fe) on DG support via linkers (O/N) called NiFe-DG. X-ray absorption spectroscopy indicates Ni/Fe metal single atoms are embedded via Fe-N4 and Ni-N4 coordination on DG surfaces. It exhibits high catalytic activity for oxygen reduction reaction (ORR) with an onset potential of 0.97 V, a half-wave potential of 0.86 V, and diffusion current density of 5.7 mA cm− 2, which is at par with commercial Pt/C. The catalyst shows superior stability, retained 82% of the initial current density even after 12 h under an applied potential of 0.86 V. Similarly, the oxygen evolution reaction (OER) overpotential of 358 mV was achieved at 10 mA cm− 2 with a lower Tafel slope value (76 mV/dec) than commercial Pt/C. It maintains 85% stability for 12 h at a constant potential of 1.588 V, shows better stability than commercial Pt/C.

The utilization of metal and nitrogen doped carbon as a Pt-free oxygen reduction electrocatalyst depends largely on the homogeneous composition of the metal–nitrogen sites with limited content. Herein a simple and feasible ammonia defective activation strategy is explored on ordered mesoporous carbon (APC) to confine hematin precursor and suppress the formation of inorganic Fe-based derivatives during pyrolysis. Thus, a hierarchically nanoporous Fe/N/APC catalyst with high numbers of exposed iron–nitrogen sites exhibits an impressive performance for oxygen reduction reaction in alkaline media, with large diffusion-limited current density and positive half-wave potential with respect to commercial Pt/C catalyst. The enhanced ORR properties can be majorly ascribed to synergistic contributions of high numbers of exposed catalytic sites completion from high contents of Fe–N and pyridinic N along with the fast mass-transport properties arising from the etched high permeable porous structure. When applied as ca...

Platinum is commonly chosen as an electrocatalyst used for oxygen reduction reaction (ORR). In this study, we report an active catalyst composed of MnO2 nanofilms grown directly on nitrogen-doped hollow graphene spheres, which exhibits high activity toward ORR with positive onset potential (0.94 V vs RHE), large current density (5.2 mA cm–2), and perfect stability. Significantly, when it was used as catalyst for air electrode, a zinc–air battery exhibited a high power density (82 mW cm–2) and specific capacities (744 mA h g–1) comparable to that with Pt/C (20 wt %) as air cathode. The enhanced activity is ascribed to the synergistic interaction between MnO2 and the doped hollow carbon nanomaterials. This easy and cheap method paves a way of synthesizing high-performance electrocatalysts for ORR.

We report an efficient method for enriching high-purity metallic single-walled carbon nanotubes (m-SWCNTs) by using NO2 as oxidant to remove semiconducting components at 220 °C. After etching, m-SWCNTs with purity higher than 90% were obtained. The surviving m-SWCNTs retain an intact structure without any extra defects on their surface.

Doping of bulk silicon and III-V materials has paved the foundation of the current semiconductor industry. Controlled doping of 2D semiconductors, which can also be used to tune their bandgap and type of carrier thus changing their electronic, optical, and catalytic properties, remains challenging. Here the substitutional doping of nonlike element dopant (Mn) at the Mo sites of 2D MoS

Large-scale implementation of electrochemical hydrogen production requires several fundamental issues to be solved, including understanding the mechanism and developing inexpensive electrocatalysts that work well at high current densities. Here we address these challenges by exploring the roles of morphology and surface chemistry, and develop inexpensive and efficient electrocatalysts for hydrogen evolution. Three model electrocatalysts are flat platinum foil, molybdenum disulfide microspheres, and molybdenum disulfide microspheres modified by molybdenum carbide nanoparticles. The last catalyst is highly active for hydrogen evolution independent of pH, with low overpotentials of 227 mV in acidic medium and 220 mV in alkaline medium at a high current density of 1000 mA cm−2, because of enhanced transfer of mass (reactants and hydrogen bubbles) and fast reaction kinetics due to surface oxygen groups formed on molybdenum carbide during hydrogen evolution. Our work may guide rational design of electrocatalysts that work well at high current densities., Hydrogen production from water provides one avenue toward harnessing renewable energy, although large-scale implementation remains a challenge. Here, authors explore roles of morphology and surface chemistry, and develop efficient catalysts for hydrogen evolution at high current densities.

Understanding the mechanisms and developing strategies toward efficient electrocatalysis at gas–liquid–solid interfaces are important yet challenging. In the past decades, researchers have devoted many efforts to improve catalyst activity by modulating electronic properties of catalysts in terms of chemical components and physical features. Herein, a mosaic catalyst, which is defined as a catalyst with spatially isolated and periodically distributed active areas, is developed to dramatically improve the activity of catalysts. Taking Pt catalyst as an example, the mosaic Pt leads to high catalytic performance, showing a specific activity 11 times higher than that of uniform Pt films for hydrogen evolution reaction (HER), as well as higher current densities than commercial Pt/C and uniform Pt films. Such a strategy is found to be general to other catalysts (e.g., 2D PtS) and other reactions (e.g., oxygen evolution reaction). The improved catalytic performance of the mosaic catalysts is attributed to enhanced mass transferability and local electric field strength, both of which are determined by the occupation ratios of catalysts. The work shines new light on manipulating electrocatalysis from the perspective of the spatial structures of catalysts, which guides the design of efficient catalysts for heterogeneous reactions.

Water electrolysis is promising for industrial hydrogen production to achieve a sustainable and green hydrogen economy, but the high cost of the technology limits its market share. Developing efficient yet economic electrocatalysts is crucial to decrease the cost of electricity and electrolytic cell. Meanwhile, electrolysis in seawater electrolyte can further reduce feedstock cost. Here we synthesize a type of electrocatalyst where trace precious metals are strongly anchored on corrosion-resistive matrix. As an example, the produced Pt/Ni-Mo electrocatalyst only needs an overpotential of 113 mV to reach an ultrahigh current density of 2000 mA cm-2 in saline-alkaline electrolyte, standing as the best performance so far. It shows high activity and long durability in various electrolytes and under harsh conditions, including strong alkaline and simulated seawater electrolytes, and under elevated temperatures up to 80 degree Celsius). This electrocatalyst is produced on a large scale at low cost and shows good performance in a commercial membrane electrode assembly stack, demonstrating its feasibility for practical water electrolysis

Doping of bulk silicon and III-V materials has paved the foundation of the current semiconductor industry. Controlled doping of 2D semiconductors, which can also be used to tune their bandgap and type of carrier thus changing their electronic, optical, and catalytic properties, remains challenging. Here the substitutional doping of nonlike element dopant (Mn) at the Mo sites of 2D MoS2 is reported to tune its electronic and catalytic properties. The key for the successful incorporation of Mn into the MoS2 lattice stems from the development of a new growth technology called dual-additive chemical vapor deposition. First, the addition of a MnO2 additive to the MoS2 growth process reshapes the morphology and increases lateral size of Mn-doped MoS2 . Second, a NaCl additive helps in promoting the substitutional doping and increases the concentration of Mn dopant to 1.7 at%. Because Mn has more valance electrons than Mo, its doping into MoS2 shifts the Fermi level toward the conduction band, resulting in improved electrical contact in field effect transistors. Mn doping also increases the hydrogen evolution activity of MoS2 electrocatalysts. This work provides a growth method for doping nonlike elements into 2D MoS2 and potentially many other 2D materials to modify their properties.

Hierarchically nanoporous N-doped carbon nanowires (N-CWs) were prepared by a novel space-confinement-induced assembly strategy, for which nitrogen-enriched pyrimidine and anodic aluminium oxide (AAO) template bearing metal oxides are employed as precursor and nanoscale channels, respectively, and the Fe/Co metal oxide not only blocks the AAO surface from the original surface-templating carbonization, but also introduces nanoporosity with acid etching. Thus-obtained carbon nanowires composed of N-doped graphene-like carbon nanosheets not only contain a high N content (up to ∼12%), but also possess a hierarchically meso/microporous structure (∼1.3 cm3 g−1) with high specific surface area (∼455 m2 g−1). This protocol allows for the simultaneous optimization of graphitization, porous structure and surface functionalization. As a result, the prepared N-CWs demonstrate an attractive electrocatalytic capability towards oxygen reduction reaction (ORR). Specifically, in addition to the improved kinetic current density and overpotential, the N-CWs prepared at 700 °C show the optimized ORR performance with an electron-transfer number of ∼4.0, which very close to that of a commercial Pt/C catalyst.

The hybrid materials of cobalt doped graphitic carbon nitride (g-C3N4) attached on single-walled carbon nanotubes (SWCNTs) were synthesized by a simple pyrolysis process. Electrochemical measurements revealed that the composites exhibited excellent electrocatalytic activity for oxygen reduction reaction (ORR), with a more positive onset potential (−0.03 V), half-wave potential (−0.15 V), high efficiency four-electron process (n = 3.97) and much higher stability than that of commercial Pt/C catalysts in alkaline media. The ORR activity mainly originates from the strong coupling of Co-g-C3N4 derived active sites on the SWCNTs.

Due to the high cost of Pt-based materials used in the electrocatalysis of the oxygen reduction reaction (ORR), an alternative composed of non-precious metals is highly desirable. Herein a hybrid with cobalt monoxide nanocrystals spatially confined in holey N-doped carbon nanowires (CoO/NCWs) was synthesized via metal oxide assisted surface pitting of chemical vapor deposited carbon nitrogen nanowires and colloidal assembly. The catalyst consists of a Co2+ enriched surface and delivers a remarkably higher ORR electrocatalytic activity and stability than its surface smooth N-doped carbon nanotube supported counterpart, with a kinetically limited current density (30.3 mA cm−2 at 0.7 V) nearly three times that of the latter. It also outperformed the commercial Pt/C catalyst. As characterized by cyclic voltammetry and XPS, the enlarged interfacial area by spatially confined hybridization is believed to be responsible for the improved ORR performance, which might create more active catalytic sites for the ORR. We propose that in-depth consideration of interfacial construction is essential when designing carbon supported metal oxide catalysts for the ORR in alkaline media.

Porous cobalt–nitrogen-doped hollow graphene spheres were prepared by a template synthesis method. As a catalyst for the oxygen reduction reaction, they exhibit an excellent electrocatalytic activity, superior methanol tolerance and strong durability, not only in alkaline solution, but also in acidic solution. The unprecedented electrocatalytic performance of the catalyst is attributed to the well-defined morphology, high specific surface area (321 m2 g−1), large pore volume (1.8 cm3 g−1) and homogeneous distribution of cobalt–nitrogen active sites.

Platinum is commonly chosen as an electrocatalyst used for oxygen reduction reaction (ORR). In this study, we report an active catalyst composed of MnO

We report an efficient method for enriching high-purity metallic single-walled carbon nanotubes (m-SWCNTs) by using NO

Carbon nanotubes were treated by high-energy ball milling processing for different milling times, and the samples were observed by HRTEM. The broken nanotubes and lots of carbon onion-like particles were obtained in the sample milled for 15 min. When the milling time was up to 60 min, carbon nanotubes turned into amorphous carbon. On the basis of HRTEM observation of carbon nanotubes and carbon nanoparticles, we discuss the possible formation mechanism of nanoparticles under the impact acting as driving force.