The practical application of graphene has still been hindered by high cost and scarcity in supply. It boosts great interest in seeking for low-cost substitute of graphene for upcoming usage where extremely physical properties are not absolutely critical. The conversion of renewable biomass offers a great opportunity for sustainable and economic fabrication of 2D carbon nanostructures. However, large-scale production of carbon nanosheets with ultrahigh aspect ratio, satisfied electronic properties, and the capability of organized assembly like graphene has been rarely reported. In this work, a facile yet efficient approach for mass production of flexible boric/nitrogen co-doped carbon nanosheets with very thin thickness of 5–8 nm and ultrahigh aspect ratio of over 6000–10 000 is demonstrated by assembling the biomass molecule in long-range order on 2D hard template and subsequent annealing. The advantage of these doped carbon nanosheets over conventional products lies in that they can be readily assembled to multilevel architectures such as freestanding flexible thin film and ultralight aerogels with better electrical properties, which exhibit exceptional capacitive performance for supercapacitor application. The recyclability of boric acid template further reduces the discharge of the waste and processing cost, rendering high cost-effectiveness and environmental benignity for scalable production.

The earth-abundant electrocatalysts with high activity are highly desired and required for high-efficient oxygen evolution reaction (OER). Herein, we report that 2D nanosheet-shaped cobalt–iron-layered double hydroxide (CoFe-LDH) is a highly active and stable oxygen evolution catalyst. The Fe³⁺ is capable of tailoring the component ranging from hydroxides to LDH and broadening the interlayer space of as-made 2D materials. Benefiting from the synergistic effects between Co and Fe species and the LDH-layered structure, the shortened ion transport distance in the nanoscale dimension, and the broader interlayer space, an enhanced mass transfer behavior for OER is demonstrated. The as-made CoFe-LDH shows high electrocatalytic activity, which is superior to those of corresponding Co(OH)₂ and the mixed phase samples of Co(OH)₂ and FeOOH, as well as RuO₂ and commercial Pt/C catalysts. Assembling CoFe-LDH on reduced graphene oxide (rGO) to configure the 2D sheet-on-sheet binary architectures (CoFe-LDH/rGO) can further create well-interconnected conductive networks within the electrode matrix, leading to the lowest overpotential of 325 mV at 10 mA cm⁻². Collectively, such integrated characteristics with alternated components will endow the as-made 2D-structured catalysts with a potential and superb superiority as low-cost earth-abundance catalysts for water oxidation.

Efficient bifunctional electrocatalysts for both the cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) are crucial for water splitting in a sustainable energy system. A strategy for fabricating strongly coupled cobalt phosphide (CoP)/graphene (G) architectures composed of CoP nanoparticles and G is described. Benefiting from synergetic effects of a dual support system of CoP for electroactive sites and G to enhance charge transfer, low overpotentials of 120 mV for the HER (0.5 m H₂SO₄) and 292 mV for the OER (1 m KOH) are required to achieve current densities of 10 mA cm⁻². The as-prepared CoP/G composites, which serve as bifunctional catalysts for both HER and OER in complete water splitting, can generate a current density of 10 mA cm⁻² at 1.626 V. The present strategy provides a novel and efficient method for configuring high-efficiency electrocatalysts for energy-related storage and conversion devices.

The front cover artwork is provided by Jieshan Qiu, Chang Yu, and co-workers, Dalian University of Technology (China). The work reports a novel approach to fabricate bifunctional electrocatalysts for full water splitting by anchoring the cobalt phosphide nanoparticles with enriched active sites onto conductive graphene matrix. Read the full text of the Article at 10.1002/celc.201600001.

High-efficiency, earth-abundant oxygen evolution reaction (OER) catalysts are highly desired and required for the half reaction of water splitting. Herein, an integrated system composed of CoMn layered double hydroxides (CoMn-LDH) and carbon nanotubes (CNTs) were configured for the OER. Ultrathin CoMn-LDH nanoplates can grow and assemble in situ on conducting CNT frameworks to form the CoMn-LDH/CNT nanoarchitectures. The CNT frameworks provide conducting channels for fast charge transfer, whereas CoMn-LDH features highly active sites and is capable of catalyzing the OER process. Benefiting from functional integration of the highly active CoMn-LDH nanoplates and the strong coupling effects between ultrathin nanoplates and conducting CNT frameworks, the as-made CoMn-LDH/CNT nanohybrids achieve excellent OER performance with a small overpotential (355 mV at 10 mA cm⁻²), low Tafel slope (45 mV dec⁻¹), and prominent electrochemical durability.

The front cover artwork is provided by Jieshan Qiu, Chang Yu, and co-workers, Dalian University of Technology (China). The work constructs an integrated system composed of ultrathin CoMn layered double hydroxides nanoplates and conductive carbon nanotube frameworks, delivering a highly electrocatalytic activity as oxygen evolution reaction catalysts. Read the full text of the Article at 10.1002/celc.201600116.

Superior electrocatalytic activities and excellent electrochemical stabilities of inexpensive counter electrodes (CEs) are crucial to the large-scale practical application of dye-sensitized solar cells (DSSCs). Herein, an efficient strategy for fabricating nitrogen-doped graphene nanoribbons (N-GNRs) via chemical unzipping of carbon nanotubes coupled with nitrogen doping process is reported, where abundant edge sites are produced and fully exposed basal planes of GNRs are activated by the N atoms within GNRs backbone. Benefiting from such unique characteristics, when first applied as CEs for DSSCs with triiodide/iodide electrolyte, a power conversion efficiency of 8.57% is delivered, outperforming GNRs (8.01%) and being superb to that of Pt (7.84%), and outstanding electrochemical stabilities of N-GNRs are also demonstrated. Density functional theory calculations reveal that the N species within GNRs matrix, especially the predominant quaternary ones, could remarkably decrease the ionization energy of GNRs, which is instrumental to transfer electrons rapidly from external circuit to triiodide, and reduce charge-transfer resistance, thus contributing to the enhanced photovoltaic performance. The present work has an insight into the unique role of N species on GNRs to the triiodide reduction, and provides an efficient strategy for design of high-efficiency carbon electrodes with fully exposed active sites in energy conversion/storage devices.

A general approach is developed for the synthesis of 2D porous carbon nanosheets (PCNS) from bio-sources derived carbon precursors (gelatin) by an integrated procedure of intercalation, pyrolysis, and activation. Montmorillonite with layered nanospace is used as a nanotemplate or nanoreactor to confine and modulate the transformation of gelatin, further leading to the formation of 2D nanosheet-shaped carbon materials. The as-made 2D PCNS exhibits a significantly improved rate performance, with a high specific capacitance of 246 F g⁻¹ and capacitance retention of 82% at 100 A g⁻¹, being nearly twice that of microsized activated carbon particulates directly from gelatin (131 F g⁻¹, 44%). The shortened ion transport distance in the nanoscaled dimension and modulated porous structure is responsible for such an enhanced superior rate capability. More importantly, the present strategy can be extended to other bio-sources to create 2D PCNS as electrode materials with high-rate performance. This will also provide a potential strategy for configuring 2D nanostructured carbon electrode materials with a short ion transport distance for supercapacitors and other carbon-related energy storage and conversion devices.

The monolithic electrodes with high volumetric capacitance demonstrate a great potential in practical industrial applications for supercapacitors. Herein, a novel strategy for ultrafast self-assembly of graphene oxides (GO)-induced monolithic NiCo–carbonate hydroxide (NiCo–CH) nanowire composite films (G–CH) is reported. The oxygen-containing functional groups on the GO surface help effectively to induce formation of the monodisperse NiCo–CH nanowires. Such a nanowire-shaped structure further functions as a scaffold and/or support, leading to 25 s of ultrafast self-assembly for G–CH composite films and a relatively loose and open channel that contributes to fast electrolyte transport. The as-obtained monolithic G–CH architectures show an excellent supercapacitor performance as binder- and conductive agent-free electrode, evidenced by a superior volumetric capacitance of 2936 F cm⁻³ and good electrochemical stability. Combining highly conductive carbon nanotubes (CNTs) into the monolithic composite films can further create well-interconnected conductive networks within the electrode matrix, thus to improve the reaction kinetics and rate capability. The present strategy that can modulate the growth of the high-electroactive pseudocapacitive hydroxides and achieve an ultrafast self-assembly of monolithic composites may pave a promising new way for development of high-performance supercapacitors and shed a new light on the configuration of carbon-based electrode materials in energy storage and conversion devices.

A facile yet effective chemical vapor deposition (CVD) method to prepare carbon nanomesh (CNM) with MgAl-layered double oxides (LDO) as sacrificial template and ferrocene as carbon precursor is reported. Due to the combined effect of the LDO template and organometallic precursor, the as-made hexagonal thin-sheet CNM features a hierarchical pore system consisting of micropores and small mesopores with a size range of 1–6 nm, and a great number of random large mesopores with a pore size of 10–50 nm. The density, geometry, and size of the pores are strongly dependent on the CVD time and the annealing conditions. As supercapacitor electrode, the CNM exhibits an enhanced capacitance, high rate capability, and outstanding cycling performance with a much-shortened time constant. The excellent capacitive performance is due to the presence of the large mesopores in the 2D CNM, which not only offer additional ion channels to accelerate the diffusion rate across the thin sheets but also help to make efficient use of the oxygen functional groups at the edges of large mesopores to increase the pseudocapacitance contribution.

The inferior rate capability and poor cycle stability of the present Li–O₂ batteries are still critical obstacles for practice applications. Configuring novel and integrated air electrode materials with unique structure and tunable chemical compositions is one of the efficient strategies to solve these bottleneck problems. Herein, a novel strategy for synthesis of 3D porous N-doped graphene aerogels (NPGAs) with frameworks constructed by interconnected nanocages with the aid of polystyrene sphere@polydopamine is reported. The interconnected nanocages as the basic building unit of graphene sheets are assembled inside the skeletons of 3D graphene aerogels, leading to the 3D NPGA with well-developed interconnected channels and the full exposure of electrochemically active sites. Benefiting from such an unique structure, the as-made NPGA delivers a high specific capacity, an excellent rate capacity of 5978 mA h g⁻¹ at 3.2 A g⁻¹, and long cycle stability, especially at a large current density (54 cycles at 1 A g⁻¹), indicative of boosted rate capability and cycle life as air electrodes for Li–O₂ batteries. More importantly, based on the total mass of C+Li₂O₂, a gravimetric energy density of 2400 W h kg⁻¹ for the NPGA–O₂//Li cell is delivered at a power density of 1300 W kg⁻¹.

Membrane capacitive deionization (MCDI) featuring both high electrosorption capacity and high energy efficiency holds promise for desalination. However, the large-scale applications of MCDI are limited greatly by the high cost of commercial ion-exchange membranes and the interfacial resistance. Here, a new strategy for high-performance MCDI is established using sulfonated graphene (SG) as cation-selective coating. A continuous ultrathin SG coating via self-assembly is formed and attached tightly onto the surface of electrospun carbon nanofibers (CNFs) by a simple yet effective dip-coating technique, yielding SG-CNF composites with a hydrophilic surface, high electrochemical specific capacitance, and greatly reduced interfacial charge transfer rate. These result in significantly enhanced capacitive deionization performance in terms of both electrosorption capacity and charge efficiency. The SG coating shows excellent cation selectivity for an asymmetric cell with SG–CNFs as a cathode. The new approach may pave a way to novel micro-MCDI, i.e. novel applications of functional graphene-based materials for high-performance, energy-efficient, and cost-effective desalination.

Asymmetric supercapacitors featuring both high energy and power densities as well as a long lifespan are much sought after and may become a reality depending on the availability of cheap yet highly active electrode materials. Here, a novel flexible architecture electrode made of NiCoAl-layered double hydroxide (NiCoAl-LDH) nanoplates coupled with NiCo-carbonate hydroxide (NiCo-CH) nanowires, grown on graphite paper via an in situ, one-step, hydrothermal method is reported. The nanowire-like NiCo-CH species in the nanoplate matrix function as a scaffold and support the dispersion of the NiCoAl-LDH nanoplates, resulting in a relatively loose and open structure within the electrode matrix. Asymmetric supercapacitors fabricated using the nanohybrids as the positive electrode and a typical activated carbon (AC) as negative electrode show a high energy density of 58.9 Wh kg⁻¹ at a power density of 0.4 kW kg⁻¹, which is based on the total mass of active materials at a voltage of 1.6 V. An energy density of 14.9 Wh kg⁻¹ can be retained even at a high power density of 51.5 kW kg⁻¹. Our asymmetric supercapacitor also exhibits an excellent long cycle life, whereby a specific capacitance of 97% is retained even after 10 000 cycles.

Stable graphene oxide monoliths (GOMs) have been fabricated by exploiting epoxy groups on the surface of graphene oxide (GO) in a ring opening reaction with amine groups of poly(oxypropylene) diamines (D₄₀₀). This method can rapidly form covalently bonded GOM with D₄₀₀ within 60 s. FTIR and XPS analyses confirm the formation of covalent C-N bonds. Investigation of the GOM formation mechanism reveals that the interaction of GO with a diamine cross-linker can result in 3 different GO assemblies depending on the ratio of D₄₀₀ to GO, which have been proven both by experiment and molecular dynamics calculations. Moreover, XRD results indicate that the interspacial distance between GO sheets can be tuned by varying the diamine chain length and concentration. We demonstrate that the resulting GOM can be moulded into various shapes and behaves like an elastic hydrogel. The fabricated GOM is non-cyctotoxic to L929 cell lines indicating a potential for biomedical applications. It could also be readily converted to graphene monolith upon thermal treatment. This new rapid and facile method to prepare covalently cross-linked GOM may open the door to the synthesis and application of next generation multifunctional 3D graphene structures.

Anatase TiO₂ nanosheets with exposed {001} facets have been controllably modified under non-thermal dielectric barrier discharge (DBD) plasma with various working gas, including Ar, H₂, and NH₃. The obtained TiO₂ nanosheets possess a unique crystalline core/amorphous shell structure (TiO₂@TiO_2−x), which exhibit the improved visible and near-infrared light absorption. The types of dopants (oxygen vacancy/surface Ti³⁺/substituted N) in oxygen-deficient TiO₂ can be tuned by controlling the working gases during plasma discharge. Both surface Ti³⁺ and substituted N were doped into the lattice of TiO₂ through NH₃ plasma discharge, whereas the oxygen vacancy or Ti³⁺ (along with the oxygen vacancy) was obtained after Ar or H₂ plasma treatment. The TiO₂@TiO_2−x from NH₃ plasma with a green color shows the highest photocatalytic activity under visible-light irradiation compared with the products from Ar plasma or H₂ plasma due to the synergistic effect of reduction and simultaneous nitridation in the NH₃ plasma.

A fast, convenient and ligand-free protocol for the synthesis of a series of 4-aryl-substituted triphenylamine derivatives by a palladium-catalysed aerobic Suzuki reaction of aryl halides with [4-(diphenylamino)phenyl]boronic acid in aqueousiPrOH is described. Importantly, both aryl bromides and heteroaryl halides afforded good to excellent yields under mild conditions.