Controllable synthesis of hollow COFs for boosting photocatalytic hydrogen generation.

COF-LZU1 with a cubic hollow structure was fabricated through a hard template approach by using water solvable NaCl as a template. The precisely prepared COF-LZU1 hollow cube displays an enhanced H2 evolution rate (651 µmol h-1 g-1), which is approximately 1.8 times greater than that of pristine COF-LZU1 (361 µmol h-1 g-1).

Hydrogen-substituted graphdiyne/graphene as an sp/sp2 hybridized carbon interlayer for lithium-sulfur batteries.

To overcome the shuttle effect in lithium-sulfur (Li-S) batteries, an sp/sp2 hybridized all-carbon interlayer by coating graphene (Gra) and hydrogen-substituted graphdiyne (HsGDY) with a specific surface area as high as 2184 m2 g-1 on a cathode is designed and prepared. The two-dimensional network and rich pore structure of HsGDY can enable the fast physical adsorption of lithium polysulfides (LiPSs). In situ Raman spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS) combined with density functional theory (DFT) computations confirm that the acetylenic bonds in HsGDY can trap the Li+ of LiPSs owing to the strong adsorption of Li+ by acetylenic active sites. The strong physical adsorption and chemical anchoring of LiPSs by the HsGDY materials promote the conversion reaction of LiPSs to further mitigate the shuttling problem. As a result, Li-S batteries integrated with the all-carbon interlayers exhibit excellent cycling stability during long-term cycling with an attenuation rate of 0.089% per cycle at 1 C over 500 cycles.

Interfacial Molecule Mediators in Cathodes for Advanced Li-S Batteries.

The complicated reactions at the cathode-electrolyte interface in Li-S batteries are a large barrier for their successful commercialization. Herein, we developed a molecular design strategy and employed three small molecules acting as interfacial mediators to the cathodes of Li-S batteries. The theoretical calculation results show that the incorporation of tris(4-fluorophenyl)phosphine (TFPP) has a strong binding performance. The experimental results demonstrate that the strong chemical interactions between polysulfides and the F, P atoms in TFPP not only modify the kinetics of the electrochemical processes in the electrolyte but also promote the formation of short-chain clusters (Li2Sx, x = 1, 2, 3, and 4) at the interface during the charge-discharge process. As a result, an optimized electrode exhibits a low capacity decay rate of 0.042% per cycle when the current rate is increased to 5 C over 1000 cycles.

Controlling the Diameter of Single-Walled Carbon Nanotubes by Improving the Dispersion of the Uniform Catalyst Nanoparticles on Substrate.

To have uniform nanoparticles individually dispersed on substrate before single-walled carbon nanotubes (SWNTs) growth at high temperature is the key for controlling the diameter of the SWNTs. In this letter, a facile approach to control the diameter and distribution of the SWNTs by improving the dispersion of the uniform Fe/Mo nanoparticles on silicon wafers with silica layer chemically modified by 1,1,1,3,3,3-hexamethyldisilazane under different conditions is reported. It is found that the dispersion of the catalyst nanoparticles on Si wafer surface can be improved greatly from hydrophilic to hydrophobic, and the diameter and distribution of the SWNTs depend strongly on the dispersion of the catalyst on the substrate surface. Well dispersion of the catalyst results in relatively smaller diameter and narrower distribution of the SWNTs due to the decrease of aggregation and enhancement of dispersion of the catalyst nanoparticles before growth. It is also found that the diameter of the superlong aligned SWNTs is smaller with more narrow distribution than that of random nanotubes.

Sulfur-doped porous reduced graphene oxide hollow nanosphere frameworks as metal-free electrocatalysts for oxygen reduction reaction and as supercapacitor electrode materials.

Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and much better methanol tolerance and durability, and to be a supercapacitor electrode material with a high specific capacitance of 343 F g(-1), good rate capability and excellent cycling stability in aqueous electrolytes. The impressive performance for ORR and supercapacitors is believed to be due to the synergistic effect caused by sulfur-doping enhancing the electrochemical activity and 3D porous hollow nanosphere framework structures facilitating ion diffusion and electronic transfer.

Self-catalytic growth of unmodified gold nanoparticles as conductive bridges mediated gap-electrical signal transduction for DNA hybridization detection.

A simple and sensitive gap-electrical biosensor based on self-catalytic growth of unmodified gold nanoparticles (AuNPs) as conductive bridges has been developed for amplifying DNA hybridization events. In this strategy, the signal amplification degree of such conductive bridges is closely related to the variation of the glucose oxidase (GOx)-like catalytic activity of AuNPs upon interaction with single- and double-stranded DNA (ssDNA and dsDNA), respectively. In the presence of target DNA, the obtained dsDNA product cannot adsorb onto the surface of AuNPs due to electrostatic interaction, which makes the unmodified AuNPs exhibit excellent GOx-like catalytic activity. Such catalytic activity can enlarge the diameters of AuNPs in the glucose and HAuCl4 solution and result in a connection between most of the AuNPs and a conductive gold film formation with a dramatically increased conductance. For the control sample, the catalytic activity sites of AuNPs are fully blocked by ssDNA due to the noncovalent interaction between nucleotide bases and AuNPs. Thus, the growth of the assembled AuNPs will not happen and the conductance between microelectrodes will be not changed. Under the optimal experimental conditions, the developed strategy exhibited a sensitive response to target DNA with a high signal-to-noise ratio. Moreover, this strategy was also demonstrated to provide excellent differentiation ability for single-nucleotide polymorphism. Such performances indicated the great potential of this label-free electrical strategy for clinical diagnostics and genetic analysis under real biological sample separation.

Removal of COD and colour in real pharmaceutical wastewater by photoelectrocatalytic oxidation method.

In this study, TiO2/Ni photo-anode and multi-walled carbon nano-tubes (MWCNTs) air cathode were prepared by the dip-coating method, and the photoelectrocatalytic degradation of real pharmaceutical wastewater was investigated in the self-made reactor. The combination of the TiO2/Ni electrode and MWCNTs air cathode was adopted to treat the pharmaceutical wastewater by the process of photoelectrocatalysis. Various operational parameters to achieve optimum efficiency of this photoelectrocatalytic degradation system are presented, such as applied bias voltage, NaCl concentration, pH and different degradation methods. Under the optimal conditions, the removal of chemical oxygen demand (COD) and colour are 93.5% and 78.5% respectively. The possible roles of the anode-cathode on the reactions and the probable mechanisms of effect were also discussed. The photoelectrocatalytic technology can be used for the long-term treatment of real pharmaceutical wastewater.

Metal-free selenium doped carbon nanotube/graphene networks as a synergistically improved cathode catalyst for oxygen reduction reaction.

The ongoing search for new non-precious-metal catalysts (NPMCs) with excellent electrocatalytic performance to replace Pt-based catalysts has been viewed as an important strategy to promote the development of fuel cells. Recent studies have proven that carbon materials doped with atoms which have a relatively small atomic size (e.g. N, B, P or S), have also shown pronounced catalytic activity. Herein, we demonstrate the successful fabrication of CNT/graphene doped with Se atoms, which has a relatively large atomic size, by a simple, economical, and scalable approach. The electrocatalytic performance of the resulting Se-doped CNT-graphene catalyst exhibits excellent catalytic activity, long-term stability, and a high methanol tolerance compared to commercial Pt/C catalysts. Our results confirmed that combining CNTs with graphene is an effective strategy to synergistically improve ORR activity. More importantly, it is also suggested that the development of graphite materials doped with Se or other heteroatoms of large size will open up a new route to obtain ideal NPMCs with realistic value for fuel cell applications.