Yurui Xue

Graphdiyne‐Supported NiCo2S4 Nanowires: A Highly Active and Stable 3D Bifunctional Electrode Material

The oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting are major energy and chemical conversion efforts. Progress in electrocatalytic reactions have shown that the future is limitless in many fields. However, it is urgent to develop efficient electrocatalysts. Here, the first graphdiyne-supported efficient and bifunctional electrocatalyst is reported using 3D graphdiyne foam as scaffolds, and NiCo2 S4 nanowires as building blocks (NiCo2 S4 NW/GDF). NiCo2 S4 NW/GDF exhibits outstanding catalytic activity and stability toward both OER and HER, as well as overall water splitting in alkaline media. Remarkably, it enables a high-performance alkaline water electrolyzer with 10 and 20 mA cm-2 at very low cell voltages of 1.53 and 1.56 V, respectively, and remarkable stability over 140 h of continuous electrolysis operation at 20 mA cm-2 . The results indicate that this catalyst has a bifunction that overcomes all reported bifunctional, nonprecious-metal-based ones.

Anchoring zero valence single atoms of nickel and iron on graphdiyne for hydrogen evolution

Electrocatalysis by atomic catalysts is a major focus of chemical and energy conversion effort. Although transition-metal-based bulk electrocatalysts for electrochemical application on energy conversion processes have been reported frequently, anchoring the stable transition-metal atoms (e.g. nickel and iron) still remains a practical challenge. Here we report a strategy for fabrication of ACs comprising only isolated nickel/iron atoms anchored on graphdiyne. Our findings identify the very narrow size distributions of both nickel (1.23 Å) and iron (1.02 Å), typical sizes of single-atom nickel and iron. The precision of this method motivates us to develop a general approach in the field of single-atom transition-metal catalysis. Such atomic catalysts have high catalytic activity and stability for hydrogen evolution reactions.Single atom catalysts provide the most efficient metal atoms usage and afford active site homogeneity, but surface attachment has proven challenging. Here, the authors use triple-bond-rich graphdiyne to anchor nickel/iron atoms and show high hydrogen evolution electrocatalysis activities.

Progress in Research into 2D Graphdiyne-Based Materials

Graphynes (GYs) are carbon allotropes with single-atom thickness that feature layered 2D structure assembled by carbon atoms with sp - and sp2 - hybridization form. Various functional theories have predicted GYs to have natural band gap with Dirac cones structure, presumably originating from inhomogeneous π-bonding between those carbon atoms with different hybridization and overlap of the carbon 2p z orbitals. Among all the GYs, graphdiyne (GDY) was the first reported to be prepared practically and, hence, attracted the attention of many researchers toward this new planar, layered material, as well as other GYs. Several approaches have been reported to be able to modify the band gap of GDY, containing invoking strain, boron/nitrogen doping, nanoribbon architectures, hydrogenation, and so on. GDY has been well-prepared in many different morphologies, like nanowires, nanotube arrays, nanowalls, nanosheets, ordered stripe arrays, and 3D framwork. The fascinating structure and electronic properties of GDY make it a potential candidate carbon material with many applications. It has recently revealed the practicality of GDY as catalyst; in rechargeable batteries, solar cells, electronic devices, magnetism, detector, biomedicine, and therapy; and for gas separation as well as water purification.

Efficient Hydrogen Production on a 3D Flexible Heterojunction Material

A novel heterojunction material, with electron-rich graphdiyne as the host and molybdenum disulfide as the catalytic center (eGDY/MDS), to produce ultraefficient hydrogen-evolution reaction (HER) at all pH values is described. It is a surprise that the metallic conductor combined from two semiconductor materials, eGDY and MDS, leads to optimal free energy (ΔGH ) and enhancement in the intrinsic HER catalytic performances. The calculated and experimental results indicate that eGDY/MDS shows greatly enhanced catalytic activities and high stabilities in both acidic and alkaline conditions; these approach the outstanding performances of the state-of-the-art noble-metal-based catalysts. The eGDY/MDS shows better activity than Pt/C in alkaline media and remarkable enhancement in photocurrent density. The high catalytic activity of eGDY/MDS originates from facilitated electronic transfer kinetics, high conductivity, more exposed catalytic active sites, and excellent mass transport.

Ultrathin Graphdiyne-Wrapped Iron Carbonate Hydroxide Nanosheets toward Efficient Water Splitting

We employed a two-step strategy for preparing ultrathin graphdiyne-wrapped iron carbonate hydroxide nanosheets on nickel foam (FeCH@GDY/NF) as the efficient catalysts toward the electrical splitting water. The introduction of naturally porous GDY nanolayers on FeCH surface endows the pristine catalyst with structural advantages for boosting catalytic performances. Benefited from the protection of robust GDY nanolayers with intimate contact between GDY and FeCH, the combined material exhibits high long-term durability of 10 000 cycles for oxygen-evolution reaction (OER) and 9000 cycles for hydrogen evolution reaction (HER) in 1.0 M KOH. Such excellent bifunctional OER/HER performance makes FeCH@GDY/NF quite qualified for alkaline two-electrode electrolyzer. Remarkably, such electrocatalyst can drive 10 and 100 mA cm-2 at 1.49 and 1.53 V, respectively. These results demonstrate the decisive role of GDY in the improvement of electrocatalytic performances, and open up new opportunities for designing cost-effective, efficient, and stable electrocatalysts for sustainable oxygen/hydrogen generation.

Group Type Analysis of Asphalt by Column Liquid Chromatography

An improved analysis method for characterization of asphalt was established. The method is based on column chromatography technique. The asphalts were separated into four groups: saturates, aromatics, resins, and asphaltenes, quantitatively. About 0.1 g of sample was required in each analysis. About 20 mL of n-heptanes was used to separate out saturates first. Then about 35 mL of n-heptanes/dichloromethane (1/2.5, v/v) mixture was used to separate out aromatics. About 30 mL of dichloromethane/tetrahydrofuran (1/3, v/v) mixture was used to separate out resin. The quality of the separation was confirmed by infrared spectra (IR) and 1H NMR analysis. The model compounds, tetracosan for saturates, dibenz(ah)anthracen for aromatics, and acetanilide for resins were used for verification. The IR and 1H NMR analysis of the prepared fractions from the column liquid chromatography were in good agreement that of pure reagents.

Controlled Synthesis of a Three-Segment Heterostructure for High-Performance Overall Water Splitting

Developing earth-abundant, highly active, and robust electrocatalysts capable of both oxygen and hydrogen evolution reactions is crucial for the commercial success of renewable energy technologies. Here we demonstrate a facile and universal strategy for fabricating transition metal (TM) sulfides by controlling the atomic ratio of TM precursors for water splitting in basic media. Density functional theory calculations reveal that the incorporation of Fe/Co can significantly improve the catalytic performance. The optimal material exhibits extremely small overpotentials of 208 mV for oxygen evolution and 68 mV for hydrogen evolution at 10 mA cm-2 with robust long-term stability. The optimized material was used as bifunctional electrodes for overall water splitting, which delivers 10 mA cm-2 at a very low cell voltage of 1.44 V with robust stability over 80 h at 100 mA cm-2 without degradation, much better than the combination of Pt and RuO2 as benchmark catalysts. The excellent water-splitting performance sheds light on the promising potential of such sulfides as high activity and robust stable electrodes.