Mu Pan

Polyaniline-functionalized carbon nanotube supported platinum catalysts.

Electrocatalytically active platinum (Pt) nanoparticles on a carbon nanotube (CNT) with enhanced nucleation and stability have been demonstrated through introduction of electron-conducting polyaniline (PANI) to bridge the Pt nanoparticles and CNT walls with the presence of platinum-nitride (Pt-N) bonding and π-π bonding. The Pt colloids were prepared through ethanol reduction under the protection of aniline, the CNT was dispersed well with the existence of aniline in the solution, and aniline was polymerized in the presence of a protonic acid (HCl) and an oxidant (NH(4)S(2)O(8)). The synthesized PANI is found to wrap around the CNT as a result of π-π bonding, and highly dispersed Pt nanoparticles are loaded onto the CNT with narrowly distributed particle sizes ranging from 2.0 to 4.0 nm due to the polymer stabilization and existence of Pt-N bonding. The Pt-PANI/CNT catalysts are electroactive and exhibit excellent electrochemical stability and therefore promise potential applications in proton exchange membrane fuel cells.

A New Core/Shell NiAu/Au Nanoparticle Catalyst with Pt-like Activity for Hydrogen Evolution Reaction.

We report a general approach to NiAu alloy nanoparticles (NPs) by co-reduction of Ni(acac)2 (acac = acetylacetonate) and HAuCl4·3H2O at 220 °C in the presence of oleylamine and oleic acid. Subject to potential cycling between 0.6 and 1.0 V (vs reversible hydrogen electrode) in 0.5 M H2SO4, the NiAu NPs are transformed into core/shell NiAu/Au NPs that show much enhanced catalysis for hydrogen evolution reaction (HER) with Pt-like activity and much robust durability. The first-principles calculations suggest that the high activity arises from the formation of Au sites with low coordination numbers around the shell. Our synthesis is not limited to NiAu but can be extended to FeAu and CoAu as well, providing a general approach to MAu/Au NPs as a class of new catalyst superior to Pt for water splitting and hydrogen generation.

Porous polyaniline-derived FeNxC/C catalysts with high activity and stability towards oxygen reduction reaction using ferric chloride both as an oxidant and iron source

A non-precious metal catalyst (NPMC), with nano-porous structure and high BET surface area, is prepared by pyrolyzing the polyaniline on carbon nanospheres using ferric chloride both as an oxidant and iron source. Electrochemical test results show that the catalyst has a high activity and much better stability than that of commercial Pt/C in acid medium.

Highly Active Platinum Nanoparticles on Graphene Nanosheets with a Significant Improvement in Stability and CO Tolerance

Graphene nanosheets (GNS) supporting Pt nanoparticles (PNs) are prepared using perfluorosulfonic acid (PFSA) as a functionalization and anchoring agent. Transmission electron microscope (TEM) results indicate that the prepared Pt NPs are uniformly deposited on GNS with a narrow particle size ranging from 1 to 4 nm in diameter. A high catalytic activity of this novel catalyst is observed by both cyclic voltammetry and oxygen reduction reaction (ORR) measurements due to the increasing of proton (H(+)) transmission channels. Significantly, this novel PFSA-functionalized Pt/GNS (PFSA-Pt/GNS) catalyst reveals a better CO oxidation and lower loss rate of electrochemical active area in comparison with that of the plain Pt/GNS and conventional Pt/C catalysts, indicating our PFSA-Pt/GNS catalysts hold much higher stability and CO tolerance by virtue of introduction of PFSA.

Bifunctional effect of reduced graphene oxides to support active metal nanoparticles for oxygen reduction reaction and stability

Highly active and stable Pt/reduced graphene oxide (RGO) electrocatalysts for the application of proton exchange membrane fuel cells were developed by tuning the O/C atom ratio of RGO supports. The results showed that Pt nanoparticles with a narrow distribution of particle sizes were well dispersed on RGO, and an increased conductivity and stability of RGO were achieved when the Pt/RGO was deoxidized with an increased graphitization degree of RGO during hydrogen reduction. The highest activity of oxygen reduction reaction (ORR) and stability of Pt/RGO was obtained by hydrogen heat treatment Pt/RGO for 1 hour, in which the O/C atom ratio was 0.14. However, with increment of the reaction time, the atom ratio of O/C decreased to 0.11, the performance dropped sharply due to the further removal of the oxygenated groups on RGO, resulting in a serious aggregation of Pt nanoparticles. This study strongly suggested a bifunctional effect of both graphitization and the oxygenated groups on the catalytic activity and stabilization of metal (such as Pt) nanoparticles on RGO. This will open a door to apply graphene in fuel cells and other fields.

Metal–Organic‐Framework‐Derived Dual Metal‐ and Nitrogen‐Doped Carbon as Efficient and Robust Oxygen Reduction Reaction Catalysts for Microbial Fuel Cells

A new class of dual metal and N doped carbon catalysts with well‐defined porous structure derived from metal–organic frameworks (MOFs) has been developed as a high‐performance electrocatalyst for oxygen reduction reaction (ORR). Furthermore, the microbial fuel cell (MFC) device based on the as‐prepared Ni/Co and N codoped carbon as air cathode catalyst achieves a maximum power density of 4335.6 mW m−2 and excellent durability.

Graphene/carbon nanospheres sandwich supported PEM fuel cell metal nanocatalysts with remarkably high activity and stability

A new strategy to synthesize novel nano-sandwiched graphene/carbon/graphene (GCG) composites is described, employing the aqueous dispersion of low cost carbon nanospheres (CNS) in graphene oxide layers with subsequent thermal reduction. This 3D GCG sandwich shows a particular exfoliated graphene morphology, with CNS regularly embedded into the graphene nanosheets (GNS), from SEM and high-resolution TEM observations. The incorporation of CNS not only increases the Brunauer–Emmett–Teller (BET) surface area due to the effective expansion of the graphene interlayer, but also enhances the electrochemically accessible surface area and the charge transfer speed at the GCG–electrolyte interfaces due to a high density of between-plane electrolyte diffusion channels, that facilitate the reaction species transport and electron transport at high rates. As a result, this unique GCG nanoarchitecture with highly dispersed Pt particles exhibits a very high electrocatalytic activity for the oxygen reduction reaction (ORR). The half cell ORR mass activity of the Pt/GCG catalyst (17.7 A g−1) is 2.2 times of that of Pt/GNS (8.2 A g−1), and 3.8 times that of commercial Pt/C catalysts (4.6 A g−1). Moreover, the Pt/GCG catalyst also shows excellent electrochemical stability. Therefore our new catalyst holds tremendous promise for potential applications in proton exchange membrane (PEM) fuel cells.

Fabrication and Performance of Polymer Electrolyte Fuel Cells by Self-Assembly of Pt Nanoparticles

Self-assembled Pt nanoparticle electrode and membrane-electrode-assembly (MEA) of polymer electrolyte fuel cells (PEFC) have been successfully prepared by using charged Pt nanoparticles. The charged Pt nanoparticles were prepared by alcoholic reduction in the presence of ionic poly(diallyldimethylammonium chloride) (PDDA) and diallyldimethylammonium chloride (DDA) stabilizers. A MEA with Pt loading of 2.8 ′ 0.1 μg cm - 2 was fabricated by the self-assembly of the charged Pt nanoparticles to the Nafion membrane surface probably via the sulfonic acid function sites, SO - 3 . The performance of the self-assembled MEA was 2.3 mW cm - 2 , corresponding to a Pt utilization of 821 W per 1 g Pt. The Pt-DDA and Pt-PDDA nanoparticle showed significant electrochemical catalytic activity for the O 2 reduction reactions. The results show that the self-assembled Pt nanoparticles were able to form a Pt monolayer and such a monolayered structure could potentially offer a powerful tool in the fundamental studies in the PEFC systems.

Understanding short-side-chain perfluorinated sulfonic acid and its application for high temperature polymer electrolyte membrane fuel cells

The great demand for high-temperature operation of polymer electrolyte membrane fuel cells (PEMFCs) has been well answered by short-side-chain perfluorinated sulfonic acid (SSC-PFSA) membranes through a good balance between transport properties and stability. It has been evidenced that fuel cells assembled with SSC-PFSA possess higher and more stable performance at elevated temperature up to 130 °C compared to that of fuel cells based on conventional long-side-chain (LSC) PFSA (Nafion®) membranes. Moreover, the shorter side-pendent chains and the absence of the ether group and of the tertiary carbon also endow SSC-PFSAs with better durability, making them more suitable for working at harsh conditions in fuel cell systems. This critical review is dedicated to summarizing the properties of SSC-PFSA and providing insight into an understanding of their micro-morphologies, mass diffusion, enhanced proton transportation and their mutual correlation. Diversified measurement techniques applied to investigate the evolution of micro-morphologies, unique diffusion and transportation properties of SSC-PFSAs are reviewed. Despite the higher crystalline and higher water absorption of SSC-PFSAs than those of LSC-PFSAs, the notably less developed and less interconnected ionic clusters in SSC-PFSAs lead to lower mass permeability, and hence the high water uptake is not as well translated into transportation performance as expected. The factors and reasons for the enhanced electrochemical performance of SSC-PFSAs such as higher proton conductivity at elevated temperatures and low humidity conditions are also discussed and understood. Highlights of recent advances in SSC-PFSA-based membranes for fuel cell applications at wider temperature ranges are summarized as general references for researchers to further prompt the development of SSC-PFSAs. The SSC-PFSAs based membranes give a bright future for the next generation of high-temperature PEMFCs.

Highly ordered and periodic mesoporous Nafion membranes via colloidal silica mediated self-assembly for fuel cells

Highly ordered and periodic mesoporous Nafion membranes with controlled structural symmetries including 2D hexagonal, 3D face-centered, 3D cubic-bicontinuous and 3D body-centered have been successfully synthesized by a novel colloidal silica mediated self-assembly method with high proton conductivity particularly under conditions of low humidity.