Jieshan Qiu

Ultralight and Highly Compressible Graphene Aerogels

Chemically converted graphene aerogels with ultralight density and high compressibility are prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials.

Enhancing lithium–sulphur battery performance by strongly binding the discharge products on amino-functionalized reduced graphene oxide

Lithium-sulphur batteries are one very appealing power source with high energy density. But their practical use is still hindered by several issues including short lifespan, low efficiency and safety concern from the lithium anode. Polysulphide dissolution and insulating nature of sulphur are generally considered responsible for the capacity degradation. However, the detachment of discharge products, that is, highly polar lithium sulphides, from nonpolar carbon matrix (for example, graphene) has been rarely studied as one critical factor. Here we report the strongly covalent stabilization of sulphur and its discharge products on amino-functionalized reduced graphene oxide that enables stable capacity retention of 80% for 350 cycles with high capacities and excellent high-rate response up to 4 C. The present study demonstrates a feasible and effective strategy to solve the long-term cycling difficulty for lithium-sulphur batteries and also helps to understand the capacity decay mechanism involved.

Carbon nanotubes as support for cathode catalyst of a direct methanol fuel cell

Colloid Interface Sci 1990;138:590–2.[4] Suzuki T, Kaneko K. Structural change of activated carbon [6] Suzuki T, Kasuh T, Kaneko K. The structural change offibers with desorption by in situ X-ray diffraction. Carbon graphitization-controlled microporous carbon upon adsorp-1988;26:743–5. tion of H O and N . Chem Phys Lett 1992;191:569–73.

Low-cost dye-sensitized solar cell based on nine kinds of carbon counter electrodes

Nine kinds of carbon materials were introduced into dye-sensitized solar cells (DSCs) system as counter electrodes (CEs). We also compared the electrochemical catalytic activity of these carbon materials with Pt for the reduction of triiodide to iodide by measuring cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel-polarization curve. The nine kinds of carbon materials in this work included synthesized well-ordered mesoporous carbon (Com), activated carbon (Ca), carbon black (Cb), conductive carbon (Cc), carbon dye (Cd), carbon fiber (Cf), carbon nanotube (Cn), discarded toner of a printer (Cp) and fullerene (C60). All carbon materials showed electrochemical catalytic activity for triiodide reduction in the DSCs system. In particular, the synthesized Com showed excellent electrochemical catalytic activity which can be comparable to the performance of Pt. After optimizing the proportion of TiO2 added into the carbon paste and the spray time of the carbon paste, the DSCs based on these carbon CEs achieved energy conversion efficiencies of 2.8–7.5%. The results demonstrate that carbon material is a promising substitute for the expensive Pt CE for low-cost DSCs.

High performance hybrid solar cells sensitized by organolead halide perovskites

Solid state hybrid solar cells with hybrid organolead halide perovskites (CH3NH3PbBr3 and CH3NH3PbI3) as light harvesters and p-type polymer poly[N-9-hepta-decanyl-2,7-carbazole-alt-3,6-bis(thiophen-5-yl)-2,5-dioctyl-2,5-di-hydropyrrolo[3,4-]pyrrole-1,4-dione] (PCBTDPP) as a hole transporting material were studied. The CH3NH3PbBr3-sensitized hybrid devices display an outstanding open circuit voltage (Voc) of ∼1.15 V, and the CH3NH3PbI3-based cells exhibit a power conversion efficiency (PCE) of ∼5.55% along with high stability. The present results show that PCBTDPP is superior to the model p-type polymer P3HT as a HTM in these hybrid solar cells to achieve remarkably high Voc and high PCE. The possible mechanisms have been suggested.

Flexible and conductive MXene films and nanocomposites with high capacitance

Significance Two-dimensional transition metal carbides (MXenes) offer a quite unique combination of excellent mechanical properties, hydrophilic surfaces, and metallic conductivity. In this first report (to our knowledge) on MXene composites of any kind, we show that adding polymer binders/spacers between atomically thin MXenes layers or reinforcing polymers with MXenes results in composite films that have excellent flexibility, good tensile and compressive strengths, and electrical conductivity that can be adjusted over a wide range. The volumetric capacitances of freestanding Ti3C2Tx MXene and its composite films exceed all previously published results. Owing to their mechanical strength and impressive capacitive performance, these films have the potential to be used for structural energy storage devices, electrochemical actuators, radiofrequency shielding, among other applications. MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti3C2Tx MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti3C2Tx/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 104 S/m in the case of the Ti3C2Tx/PVA composite film and 2.4 × 105 S/m for pure Ti3C2Tx films. The tensile strength of the Ti3C2Tx/PVA composites was significantly enhanced compared with pure Ti3C2Tx or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm3 for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.

A Flexible TiO2(B)‐Based Battery Electrode with Superior Power Rate and Ultralong Cycle Life

A flexible film electrode is fabricated by growing TiO2 (B) nanosheets on electrospun carbon nanofiber fabric. The hybrid electrode exhibits remarkable electrochemical performance with high reversible capacity, excellent rate capability, and ultralong cycle life for thousands of cycles, which makes it highly attractive for high-power flexible lithium-ion batteries.

Electroactive edge site-enriched nickel–cobalt sulfide into graphene frameworks for high-performance asymmetric supercapacitors

Tailor-made edge site-enriched inorganics coupled graphene hybrids hold a promising platform material for high-performance supercapacitors. Herein, we report a simple strategy for fabricating edge site-enriched nickel–cobalt sulfide (Ni–Co–S) nanoparticles decorated on graphene frameworks to form integrated hybrid architectures (Ni–Co–S/G) via an in situ chemically converted method. The Kirkendall effect-involved anion exchange reaction, e.g. the etching-like effort of the S2− ions, plays a crucial role for the formation of the edge site-enriched nanostructure. Density functional theory (DFT) calculations reveal that the Ni–Co–S edge sites have a high electrochemical activity and strong affinity for OH− in the electrolyte, which are responsible for the enhanced electrochemical performance. Benefiting from the integrated structures of Ni–Co–S nanoparticles and conductive graphene substrates, the resultant Ni–Co–S/G hybrid electrodes exhibit a high specific capacitance of 1492 F g−1 at the current density of 1 A g−1, a superior rate capability of 96% when the current density is increased to 50 A g−1, and excellent electrochemical stabilities. An asymmetric supercapacitor fabricated using the edge site-enriched Ni–Co–S/G hybrids as the positive electrode and porous carbon nanosheets (PCNS) as negative electrodes shows a high energy density of 43.3 W h kg−1 at a power density of 0.8 kW kg−1, and an energy density of 28.4 W h kg−1 can be retained even at a high power density of 22.1 kW kg−1.

Investigation of factors affecting adsorption of transition metals on oxidized carbon nanotubes.

Adsorption of nickel, copper, zinc and cadmium from aqueous solutions on carbon nanotubes oxidized with concentrated nitric acid was carried out in single, binary, ternary and quaternary systems. TEM and adsorption of nitrogen were used to determine texture and structural parameters, respectively. The surface chemistry was evaluated using the pH at the point of zero charge, FTIR spectroscopy and XPS analysis. The experimental results showed that all isotherms for Cu(2+)(aq) fit to Langmuir model in each system. On the other hand, the isotherms for Ni(2+)(aq), Cd(2+)(aq) and Zn(2+)(aq) in multi-component systems reveal the effect of competition for adsorption sites seen as a decrease in the amount adsorbed. The uptakes at the equilibrium concentration of 0-0.04 mmol L(-1) in single system and 0-0.15 mmol L(-1) in binary system are in the order Cu(2+)(aq)>Ni(2+)(aq)>Cd(2+)(aq)>Zn(2+)(aq) while for the ternary and quaternary, the order is Cu(2+)(aq)>Cd(2+)(aq)>Zn(2+)(aq)>Ni(2+)(aq). The results indicate that the mechanism of adsorption is governed by the surface features, ion exchange process and electrochemical potential. The latter plays a significant role in multi-component adsorption where redox reactions, not only on the adsorbent surface but also between the adsorbates, are likely to occur.

Hierarchical activated carbon nanofiber webs with tuned structure fabricated by electrospinning for capacitive deionization

Novel hierarchical activated carbon nanofiber (ACF) webs with tuned structure have been fabricated by incorporating carbon black (CB) into an electrospun polymer solution, followed by heat treatment. The as-made electrospun ACF webs show superior capacities as electrode materials in capacitive deionization (CDI) for desalination due to their advantageous hierarchical structures.