Ruihong Wang

Controllable synthesis of graphitic carbon nanostructures from ion-exchange resin-iron complex via solid-state pyrolysis process

Graphitic carbon nanocapsules, nanosheets and nanoplates were selectively obtained via a solid-state pyrolysis route from various ion-exchange resin-iron complexes.

A facile route to carbide-based electrocatalytic nanocomposites

Tungsten carbide nanoparticles with diameters less than 10 nm on graphitic carbon (WC@GC) produced from green foxtail grass under catalysis of iron salts have been successfully synthesized by an efficient method for the first time. The materials were characterized by physical and electrochemical techniques. The results showed that the Pt particles and WC on GC have excellent properties as an electrocatalyst for methanol oxidation. The Pt/WC@GC electrocatalyst is over 5 times higher in peak current density at 0.4 V, and 100 mV more negative in onset potential for methanol oxidation reaction than that on the commercial Pt/C electrocatalyst. Since Pt/WC@GC carries higher catalytic activity compared with Pt/C due to its synergistic effect, less Pt will be required for the same performance and it will in turn reduce the cost of fuel cell electrocatalyst. This work demonstrated that the natural plants could be used to uptake targeting precursors for preparing functional materials. The present method is simple, rapid, and scalable to mass production of the nanomaterials. WC@GC is an applicable support material since the composite carbide and graphite particles are electrically conductive and consist of stable components.

Synthesis of Pd on porous hollow carbon spheres as an electrocatalyst for alcohol electrooxidation

Porous hollow carbon spheres (PHCSs) are prepared with glucose as the carbon source and a solid core microporous shell silica (SCMSS) as the template. The PHCSs are composed of broken and complete hollow carbon spheres cemented to each other. There are big gaps between the PHCSs which make it possible to utilize the inner wall of the hollow carbon spheres as an electrocatalyst support. The PHCSs have a high Brauner–Emett–Teller (BET) surface area of 998.1 m2 g−1, and a pore volume of 1.88 cm3 g−1. The Pd nanoparticles supported on PHCS electrocatalysts are highly active for methanol, ethanol and isopropanol electrooxidation. Pd/PHCS has a 3.1 times higher in peak current density and a 80 mV negatively shifted onset potential compared with that of a Pd/C electrocatalyst at the same Pd loadings for ethanol electrooxidation. The porous structure of Pd/PHCS is favorable for mass transfer and remains high activity in higher concentration of ethanol. The Pd/PHCS electrocatalyst is a potential candidate for application in direct liquid alcohol fuel cells.

Chitosan: a green carbon source for the synthesis of graphitic nanocarbon, tungsten carbide and graphitic nanocarbon/tungsten carbide composites

In this paper, a simple approach was proposed to fabricate graphitic carbon nanocapsules, tungsten carbide and tungsten carbides/graphitic carbon composites by using chitosan, a green and renewable biopolymer, as a carbon source. The route includes, first, fabrication of the precursors that consist of chitosan coordinated with a certain metal ion (or metal complex anion) followed by carbonizing the precursors under N(2) atmosphere. The composition of the final products could be regulated by changing the type and ratio of the metal source (cations or complex anions) combined with the chitosan in the precursors. The experimental results showed that uniform carbon nanocapsules could be obtained when Ni(2+) was introducing in the precursors, while incorporating [PW(12)O(40)](3-) (PW(12)) with chitosan led to the formation of WC nanoparticles. As the Ni(2+) and PW(12) are simultaneously coordinated with chitosan, the composites of tungsten carbide/graphitic carbon were successfully produced. Transmission electron microscopy (TEM) analysis revealed that the graphitic carbon nanocapsules are about 45 nm in diameter; uniform WC nanoparticles with a average size of 40 nm are observed. Moreover, the particle size of WC in the tungsten carbide/graphitic carbon composite is about 10 nm, which is smaller than that of the pure WC particles. Furthermore, the performance of the sample-loaded Pt nanoparticles for methanol electro-oxidation was studied in detail. The results indicated that the samples could act as good carriers for Pt in the methanol electro-oxidation reaction with high effectivity and improved stability.

Fe3O4/rGO nanocomposite: synthesis and enhanced NOx gas-sensing properties at room temperature

We demonstrate a facile fabrication of Fe3O4 nanoparticle (NP)–decorated reduced graphene oxide (Fe3O4/rGO) nanocomposites and their application for the fast and selective detection of NOx at room temperature. The as-synthesized nanocomposites have layered structures and the Fe3O4 NPs with diameters ranging from 30 to 50 nm were evenly loaded on the rGO surface. Furthermore, the Fe3O4/rGO nanocomposite based gas sensor exhibits excellent sensitivity and fast response to NOx gas at room temperature. Moreover, for a NOx concentration of 97.0 ppm, the observed value of sensitivity was about 35.6%, while the response time was 29.3 s. We found that the loading density of the Fe3O4 NPs greatly affects the sensing performance of the Fe3O4/rGO nanocomposites and a suitable NP loading leads to the highest sensitivity. The synthesis method to produce rGO-based nanocomposites as novel gas sensor materials has great potential to push low cost and gas sensing nanotechnology.

An In2O3 nanorod-decorated reduced graphene oxide composite as a high-response NOx gas sensor at room temperature

A novel composite room temperature gas sensor based on an In2O3 nanorod-decorated reduced graphene oxide composite (In2O3 NR/rGO composite) was successfully synthesized via a facile reflux method. In this synthesis, In3+ and urea were adsorbed on GO through electrostatic interactions in a water solution. The subsequent reflux treatment led to the transformation of the In(OH)3 nanorods coated on GO and also to the reduction of graphene oxide. We demonstrate that the composite can detect NOx gas with a response of 1.45, a fast response time of 25.0 s for 97.0 ppm NOx and a low detection limit of 970 ppb at room temperature. Compared with the pure In2O3 NRs, the composite has a faster response within 30.0 s over the whole range of NOx concentration. The enhanced sensing properties are attributed to the synergy of the superior conductivity of rGO and the nanostructure of the In2O3 NR/rGO composite. The present strategy for combining various hydroxide and nanoscale building blocks into integrated 3D structures will open new opportunities for designing and synthesizing multifunctional composites.

Pt loaded onto silicon carbide/porous carbon hybrids as an electrocatalyst in the methanol oxidation reaction

Silicon carbide/porous carbon (SiC–PC) hybrids were directly synthesized via a facile evaporation-induced assembly approach combined with in situ carbothermal reduction in which soluble formaldehyde resin, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and tetraethoxysilane were used as the source of carbon, the porogent and the source of silicon, respectively. The synthetic SiC–PC hybrid had a large specific surface area of 1163 m2 g−1 and the 10 nm SiC nanoparticles were well dispersed on the PC material. After loading with Pt nanoparticles, the resulting Pt/Si–PC catalyst had the highest reported unit mass electroactivity (836.93 A g−1 Pt) towards methanol electrooxidation (3.05 and 3.61 times the electroactivity of commercial PtRu/C and Pt/C catalysts). The Pt/SiC–PC catalyst also had a better stability than commercial PtRu/C and Pt/C catalysts. This enhanced electrocatalytic activity is attributed not only to the mutual effect of the hybrid support and the metal nanoparticles, but also to the large surface area that allows Pt to be used efficiently and gives the mass transportation required in a porous electrode. These results indicate that SiC–PC hybrids have great potential as high-performance catalyst supports for fuel cell electrocatalysts.