Ze Yang

Hydrogen substituted graphdiyne as carbon-rich flexible electrode for lithium and sodium ion batteries

Organic electrodes are potential alternatives to current inorganic electrode materials for lithium ion and sodium ion batteries powering portable and wearable electronics, in terms of their mechanical flexibility, function tunability and low cost. However, the low capacity, poor rate performance and rapid capacity degradation impede their practical application. Here, we concentrate on the molecular design for improved conductivity and capacity, and favorable bulk ion transport. Through an in situ cross-coupling reaction of triethynylbenzene on copper foil, the carbon-rich frame hydrogen substituted graphdiyne film is fabricated. The organic film can act as free-standing flexible electrode for both lithium ion and sodium ion batteries, and large reversible capacities of 1050u2009mAhu2009g−1 for lithium ion batteries and 650u2009mAhu2009g−1 for sodium ion batteries are achieved. The electrode also shows a superior rate and cycle performances owing to the extended π-conjugated system, and the hierarchical pore bulk with large surface area.Flexible batteries have been used to power wearable smart electronics and implantable medical devices. Here, the authors report a carbon-rich flexible hydrogen substituted graphdiyne electrode exhibiting superior electrochemical performance in lithium and sodium ion batteries.

Nitrogen-Doped Porous Graphdiyne: A Highly Efficient Metal-Free Electrocatalyst for Oxygen Reduction Reaction

Metal-free catalysts for oxygen reduction reaction (ORR) are the desired materials for low-cost proton exchange membrane fuel cells. Graphdiyne (GDY), a novel type of two-dimensional carbon allotrope, is featured by its sp- and sp2-hybridized carbon atoms, different from the other existing carbon materials. Thus, nitrogen (N) can be doped in new styles by substituting sp-hybridized carbon atoms, effective for ORR, which has been displayed in this study using both experimental and theoretical technologies. The N-doped GDY was synthesized with pyridine and NH3 as N sources successively, expressing an electrocatalytic activity at a potential above 0.8 V similar to that of commercial Pt/C for ORR in alkaline solution and higher stability and better methanol tolerance than those of Pt/C.

Synthesis of Chlorine-Substituted Graphdiyne and Applications for Lithium-Ion Storage

Chlorine-substituted graphdiyne (Cl-GDY) is prepared through a Glaser-Hay coupling reaction on the copper foil. Cl-GDY is endowed with a unique π-conjugated carbon skeleton with expanded pore size in two dimensions, having graphdiyne-like sp- and sp2 - hybridized carbon atoms. As a result, the transfer tunnels for lithium (Li) ions in the perpendicular direction of the molecular plane are enlarged. Moreover, benefiting from the bottom-to-up fabrication procedure of graphdiyne and the strong chemical tailorability of the alkinyl-contained monomer, the amount of substitutional chlorine atoms with appropriate electronegativity and atom size is high and evenly distributed on the as-prepared carbon framework, which will synergistically stabilize the Li intercalated in the Cl-GDY framework, and thus generate more Li storage sites. Profiting from the above unique structure, Cl-GDY shows remarkable electrochemical properties in lithium ion half-cells.

A Delicately Designed Sulfide Graphdiyne Compatible Cathode for High‐Performance Lithium/Magnesium–Sulfur Batteries

Novel sulfur cathodes hold the key to the development of metal-sulfur batteries, the promising candidate of next-generation high-energy-storage systems. Herein, a fascinating sulfur cathode based on sulfide graphdiyne (SGDY) is designed with a unique structure, which is composed of a conducting carbon skeleton with high Li+ mobility and short sulfur energy-storing unites. The SGDY cathode can essentially avoid polysulfide dissolution and be compatible with commercially available carbonate-based electrolytes and Grignard reagent-based electrolytes (all phenyl complex (APC) type electrolytes). Both the assembled Li-S and Mg-S batteries exhibit excellent electrochemical performances including large capacity, superior rate capability, high capacity retention, and high Coulombic efficiency. More importantly, this is the first implementation case of a reliable Mg-S system based on nucleophilic APC electrolytes.

Preparation of 3D Architecture Graphdiyne Nanosheets for High-Performance Sodium-Ion Batteries and Capacitors

Here, we apply three-dimensional (3D) architecture graphdiyne nanosheet (GDY-NS) as anode materials for sodium-ion storage devices achieving high energy and power performance along with excellent cyclic ability. The contribution of 3D architecture nanostructure and intramolecular pores of the GDY-NS can substantially optimize the sodium storage behavior through the accommodated intramolecular pore, 3D interconnective porous structure, and increased activity sites to facilitate a fast sodium-ion-diffusion channel. The contribution of butadiyne linkages and the formation of a stable solid electrolyte interface layer are directly confirmed through the in situ Raman measurement. The GDY-NS-based sodium-ion batteries exhibit a stable reversible capacity of approximately 812 mAh g-1 at a current density of 0.05 A g-1; they maintain more than 405 mAh g-1 over 1000 cycles at a current density of 1 A g-1. Furthermore, the sodium-ion capacitors could deliver a capacitance more than 200 F g-1 over 3000 cycles at 1 A g-1 and display an initial specific energy as high as 182.3 Wh kg-1 at a power density of 300 W kg-1 and maintain specific energy of 166 Wh kg-1 even at a power density of 15u2009000 W kg-1. The high energy and power density along with excellent cyclic performance based on the GDY-NS anode offers a great potential toward application on next-generation energy storage devices.

Graphdiyne Containing Atomically Precise N Atoms for Efficient Anchoring of Lithium Ion

The qualitative and quantitative nitrogen-doping strategy for carbon materials is reported here. Novel porous nanocarbon networks pyrimidine-graphdiyne (PM-GDY) and pyridine-graphdiyne (PY-GDY) films with large areas were successfully prepared. These films are self-supported, uniform, continuous, flexible, transparent, and quantitively doped with merely pyridine-like nitrogen (N) atoms through the facile chemical synthesis route. Theoretical predictions imply these N doped carbonaceous materials are much favorable for storing lithium (Li)-ions since the pyridinic N can enhance the interrelated binding energy. As predicted, PY-GDY and PM-GDY display excellent electrochemical performance as anode materials of LIBs, such as the superior rate capability, the high capacity of 1168 (1165) mA h g-1 at current density of 100 mA g-1 for PY-GDY (PM-GDY), and the excellent stability of cycling for 1500 (4000) cycles at 5000 mA g-1 for PY-GDY (PM-GDY).

Selectively nitrogen-doped carbon materials as superior metal-free catalysts for oxygen reduction

Doping with pyridinic nitrogen atoms is known as an effective strategy to improve the activity of carbon-based catalysts for the oxygen reduction reaction. However, pyridinic nitrogen atoms prefer to occupy at the edge or defect sites of carbon materials. Here, a carbon framework named as hydrogen-substituted graphdiyne provides a suitable carbon matrix for pyridinic nitrogen doping. In hydrogen-substituted graphdiyne, three of the carbon atoms in a benzene ring are bonded to hydrogen and serve as active sites, like the edge or defect positions of conventional carbon materials, on which pyridinic nitrogen can be selectively doped. The as-synthesized pyridinic nitrogen-doped hydrogen-substituted graphdiyne shows much better electrocatalytic performance for the oxygen reduction reaction than that of the commercial platinum-based catalyst in alkaline media and comparable activity in acidic media. Density functional theory calculations demonstrate that the pyridinic nitrogen-doped hydrogen-substituted graphdiyne is more effective than pyridinic nitrogen-doped graphene for oxygen reduction.Doping carbon-based materials with nitrogen is effective for enhancing catalytic activity for oxygen reduction; however, directing nitrogen dopants to specific locations is difficult. Here the authors employ hydrogen-substituted graphdiyne as a matrix for nitrogen doping, leading to enhanced performance.

Fluoride graphdiyne as a free-standing electrode displaying ultra-stable and extraordinary high Li storage performance

In natural two-dimensional (2D) materials (such as graphene, transition metal dichalcogenides and transition metal carbides), energy and power density are inevitably hindered by Li ion diffusion perpendicular to the compact atomic layer. At the same time, their cycling stability is affected by side reactions due to the large specific surface area and high activity of surface atoms. Here we report the preparation of a new 2D carbon rich framework called fluoride graphdiyne (F-GDY). The experiments, together with theoretical calculations, show that extraordinarily high reversible capacity (1700 mA h g−1) and extremely stable cycle performance (9000 cycles) are achieved by the reversible transition between C–F semi-ionic bonds and ionic bonds at the plateaus of 0.9 V. This bottom-up strategy offers a versatile approach to the rational design of ultra-stable flexible 2D materials through solution-based processability for application in the efficient electrodes of high performance rechargeable batteries.