Jianyu Cao

Preparation of graphene-supported highly dispersed nickel nanoparticles for the improved generation of hydrogen from ball-milled LiBH4

Using a hydrogen thermal reduction method, highly dispersed nickel nanoparticles (ca. 9.7 nm) were uniformly supported on graphene (Ni/G), and then ball-milled with LiBH4 to investigate in depth their hydrogen storage behaviour. The Ni/G-doped system exhibited high gravimetric hydrogen capacity, excellent rehydrogenation reversibility and rapid kinetics, due to the synergistic effect of nanoconfinement in graphene and catalysis by Ni nanoparticles, demonstrating a promising strategy for the effective design of hydrogen storage materials using LiBH4. In the case of doping with 20 wt.% Ni/G, thermal dehydrogenation of LiBH4 began around 180 °C, and the main hydrogen release peaks occurred at 275 and 465 °C, with a total weight loss of 15.2 wt.%. At 450 °C, about 12.8 wt.% hydrogen was desorbed in 45 min. More importantly, the hydrogen released during a second dehydrogenation remained at 12.6 wt.%, and a steady hydrogen capacity of ca. 9.8 wt.% was achieved during the thirtieth hydrogen uptake–release cycle under 3 MPa H2 at 400 °C, demonstrating the effectiveness of the Ni/G catalyst in the reversibility of hydrogen uptake of LiBH4 at relatively lower temperatures and pressure. During this process LiBH4 was re-formed and a new product, Li2B12H12, was detected following rehydrogenation.

The growth, thermal and nonlinear optical properties of single-crystal GdAl3(BO3)4

The nonlinear optical single-crystals GdAl3(BO3)4 (GAB), space group R32, were grown by the top-seed solution growth (TSSG) method. The thermal properties and the nonlinear optical characteristics have been investigated. The two principal coefficients of thermal expansion along (100) and (001) were measured to be 5.30 × 10−6, 1.88 × 10−5 K−1. The transmission spectrum was measured and the second-harmonic generation (SHG) was presented. By way of our designed cross superimposed laser crystal multiplier, the frequency doubling laser at wavelength 457.5 nm was measured to be 18.2 mW and the facular properties indicated the multiplier contributed to the improvement of the frequency doubling conversion efficiency.

Facile preparation of mesoporous graphenes by the sacrificial template approach for direct methanol fuel cell application

Mesoporous graphenes (MGs) were synthesized via a template-assisted pyrolysis approach and employed to fabricate a cathodic diffusion layer for direct methanol fuel cell (DMFC) application. Phenolic polymer-ammonium oleate supramolecular aggregates that formed by weak acid–base interaction induced self-assembly resulted in a solid carbon source. Layered graphitic carbon nitrides (g-C3N4) created under high temperature and a nitrogen gas environment provided the sacrificial template. The MGs were shown to have a specific mesopore surface area of 265.9 m2 g−1 with large bimodal mesopore diameters of approximately 4 and 10 nm. Mesopores were generated by the in situ formation and decomposition of a g-C3N4 template. The passive DMFC fabricated by the use of MGs in the cathodic diffusion layer demonstrated a peak power density of 32.9 mW cm−2, which is approximately 1.2 times higher than that with Vulcan XC-72R carbon black. The outstanding characteristics of MGs as a material that can be used as a porous diffusion layer for DMFCs verify the great potential for use in energy-related fields.

Spectroscopic properties of Ho3+ doped CaNb2O6 crystal

Abstract Results of the growth and annealing processes of Ho3+:CaNb2O6 crystal with high oxygen defects were reported. The spectroscopic properties of Ho3+:CaNb2O6 were also analysed, and the decay curves of the bulk and powder samples in correspondence with the emission 5I7→5I8 at 2·0 μm were recorded. The effects of radiative trapping on the final results were also indicated, and the final value of the fluorescence lifetimes of 5I7→5I8 transition is calculated to be 5·19 ms. CaNb2O6 crystal was shown to be a prospective material for an infrared laser medium at 2·0 μm.

Fe–N co-decorated hierarchically porous graphene as a highly efficient electrocatalyst for the oxygen reduction reaction

Fe–N co-decorated hierarchically porous graphene (FeN/G) was prepared by a facile one-step pyrolysis method. In the pyrolysis synthesis process, dicyandiamide was introduced as a nitrogen precursor and sacrificial templating agent, together with ferric nitrate utilized as an iron precursor, to aid in the formation of graphene nanosheets and their self-assembly into an interconnected porous framework. Consequently, the resultant FeN/G framework shows a relatively large specific surface area (401.1 m2 g−1), hierarchically porous structure and abundant meso-/macropores. Such highly desired FeNC structures not only possess sufficient catalytically active sites for the oxygen reduction reaction (ORR) but also guarantee fast transfer of reactants and ions, which provides excellent catalytic activity with positive onset and half-wave potentials, large kinetic-limiting current density, and remarkable durability that is obviously better than the commercial Pt/C in alkaline medium.

Nitrogen-doped porous graphene as a highly efficient cathodic electrocatalyst for aqueous organic redox flow battery application

The redox flow battery (RFB) is considered one of the most attractive energy storage technologies because of its high efficiency, long service life and great safety. In this work, nitrogen-doped porous graphene (NPG) was achieved by embedding nitrogen atoms into the graphitic matrix via a sacrificial-template-assisted pyrolysis approach, and then was employed to catalyze electrochemically the redox reaction of 1,2-dihydrobenzoquinone-3,5-disulphonic acid (BQDSH2) for aqueous organic RFB application. The electrocatalytic performances of this catalyst toward the BQDS/BQDSH2 redox couple were greatly enhanced, including a 6.7 times higher rate constant and much lower peak potential separation value compared to those of a glassy carbon electrode. Furthermore, a 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/BQDS RFB with NPGs as the cathodic BQDS/BQDSH2 catalyst exhibited a maximum power density of ca. 62.4 mW cm−2, about 3.3 times higher than that of the pristine RFB without NPGs, and a minimal discharge capacity fade during the cycling test. The abundant nitrogen defects in NPGs are beneficial to the BQDS/BQDSH2 redox reaction by providing active sites and enhancing the transfer rate of protons and reactants, contributing to the improvement of AQDS/BQDS RFB performance.

Highly Dispersed Pt Nanoparticles Supported on Mesoporous Carbon and Its Electrocatalytic Performance for Ethylene Glycol Oxidation

Mesoporous carbon (MC) with high mesopore content and narrow pore size distribution was prepared using colloidal silica as hard template and Pluronic F127 triblock copolymer as soft template, re- spectively. Then highly dispersed Pt catalyst supported on MC was achieved by ethylene glycol (EG) reduc- tion method. Electrooxidation behavior of EG on the Pt/MC catalyst electrode in sulfuric solution was inves- tigated using cyclic voltammogram (CV), chronoamperometry, linear sweeping voltammogram (LSV) and electrochemical impedance spectra (EIS) analysis. The experimental results indicate that the electrocatalytic performance of the Pt/MC catalyst for EG oxidation is much higher than that of Pt/XC72R catalyst. EIS analysis further reveals that the electrooxidation reaction of EG on the Pt/MC catalyst electrode has a lower charge-transfer resistance. The higher electrocatalytic activity of the Pt/MC catalyst may be due to the pro-