Platinum-based nanostructured materials: synthesis, properties, and applications.

Cost-effective electrocatalysts for the oxygen evolu- tion reaction (OER) are critical to energy conversion and storage processes. A novel strategy is used to synthesize a non- noble-metal-based electrocatalyst of the OER by finely com- bining layered FeNi double hydroxide that is catalytically active and electric conducting graphene sheets, taking advant- age of the electrostatic attraction between the two positively charged nanosheets. The synergy between the catalytic activity of the double hydroxide and the enhanced electron transport arising from the graphene resulted in superior electrocatalytic properties of the FeNi-GO hybrids for the OER with over- potentials as low as 0.21 V, which was further reduced to 0.195 V after the reduction treatment. Moreover, the turnover frequency at the overpotential of 0.3 V has reached 1 s 1 , which is much higher than those previously reported for non-noble- metal-based electrocatalysts. The growing demand for energy and the increasing concerns about environment pollution from fossil fuels are stimulating intense research interest in energy conversion and storage from alternative sustainable energy sources. As one of the most important process to produce and store renewable energy in chemical form, the oxygen evolution reaction (OER) has led to many studies in recent years. However, the kinetics of OER is sluggish. Therefore, an effective electro- catalyst is needed to accelerate the reaction and reduce the large overpotential and thus improve the energy conversion efficiency. Metal oxides are the most active and durable electrocatalysts for OER, among which IrO2 and RuO2 are thought to be best OER catalysts in both acidic and alkaline solutions. (1) However, the high cost and element scarcity greatly hindered the widespread use of these noble-metal oxide catalysts. Therefore, it is desirable to develop efficient alternative catalysts based on inexpensive and earth-abun- dant elements without compromising good catalytic activity and durability for OER. Recently, extensive efforts have been made to use perovskites (2) and first-row transition-metal- based materials (3) as low-cost catalysts or electrode materials

A Strongly Coupled Graphene and FeNi Double Hydroxide Hybrid as an Excellent Electrocatalyst for the Oxygen Evolution Reaction

Polyaniline nanostructures and the role of aniline oligomers in their formation

Insufficient catalytic activity and durability are key barriers to the commercial deployment of low temperature polymer electrolyte membrane (PEM) and direct-methanol fuel cells (DMFCs). Recent observations suggest that carbon-based catalyst support materials can be systematically doped with nitrogen to create strong, beneficial catalyst-support interactions which substantially enhance catalyst activity and stability. Data suggest that nitrogen functional groups introduced into a carbon support appear to influence at least three aspects of the catalyst/support system: 1) modified nucleation and growth kinetics during catalyst nanoparticle deposition, which results in smaller catalyst particle size and increased catalyst particle dispersion, 2) increased support/catalyst chemical binding (or “tethering”), which results in enhanced durability, and 3) catalyst nanoparticle electronic structure modification, which enhances intrinsic catalytic activity. This review highlights recent studies that provide broad-based evidence for these nitrogen-modification effects as well as insights into the underlying fundamental mechanisms.

Enhancement of Pt and Pt-alloy fuel cell catalyst activity and durability via nitrogen-modified carbon supports

Graphene nanoplatelets have been synthesized by thermal exfoliation of graphitic oxide and nitrogen doped graphene nanoplatelets have been obtained by nitrogen plasma treatment. Graphene nanoplatelets and nitrogen doped graphene nanoplatelets have been used as a catalyst support for platinum nanoparticles for oxygen reduction reactions in proton exchange membrane fuel cells. Platinum nanoparticles were dispersed over these support materials using the conventional chemical reduction technique. The morphology and structure of the graphene based powder samples were studied using X-ray diffraction, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A full cell was constructed with platinum loaded nitrogen doped graphene nanoplatelets and the results have been compared with platinum loaded graphene nanoplatelets. A maximum power density of 440 and 390 mW cm−2 has been obtained with platinum loaded nitrogen doped graphene and platinum loaded graphene nanoplatelets as ORR catalysts respectively. Nitrogen plasma treatment created pyrrolic nitrogen defects, which act as good anchoring sites for the deposition of platinum nanoparticles. The improved performance of fuel cells with N-G as catalyst supports can be attributed to the increased electrical conductivity and improved carbon–catalyst binding.

Nitrogen doped graphene nanoplatelets as catalyst support for oxygen reduction reaction in proton exchange membrane fuel cell

Efficient anchorage of Pt clusters on N-doped carbon nanotubes and their catalytic activity

We report the preparation of hybrid paperlike films consisting of alternating layers of graphene (or graphene oxide) and different types of multiwalled carbon nanotubes (N-doped MWNTs, B-doped MWNTs, and pristine MWNTs). We used an efficient self-assembly method in which nanotubes were functionalized with cationic polyelectrolytes in order to make them dispersible in water, and subsequently these suspensions were mixed with graphene oxide (GO) suspensions, and the films were formed by casting/evaporation processes. The electronic properties of these films (as produced and thermally reduced) were characterized, and we found electrical resistivities as low as 3 × 10–4 Ω cm. Furthermore, we observed that these films could be used as electron field emission sources with extraordinary efficiencies; threshold electric field of ca. 0.55 V/μm, β factor as high as of 15.19 × 103, and operating currents up to 220 μA. These values are significantly enhanced when compared to previous reports in the literature for oth...

Takuya Hayahsi

Papers

Efficient anchorage of Pt clusters on N-doped carbon nanotubes and their catalytic activity

Large Area Films of Alternating Graphene–Carbon Nanotube Layers Processed in Water