Daping He

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.

Ultrathin Icosahedral Pt-Enriched Nanocage with Excellent Oxygen Reduction Reaction Activity

Cost-efficient utilization of Pt in the oxygen reduction reaction (ORR) is of great importance for the potential industrial scale demand of proton-exchange membrane fuel cells. Designing a hollow structure of a Pt catalyst offers a great opportunity to enhance the electrocatalytic performance and maximize the use of precious Pt. Herein we report a routine to synthesize ultrathin icosahedral Pt-enriched nanocages. In detail, the Pt atoms were conformally deposited on the surface of Pd icosahedral seeds, followed by selective removal of the Pd core by a concentrated HNO3 solution. The icosahedral Pt-enriched nanocage that is a few atomic layers thick includes the merits of abundant twin defects, an ultrahigh surface/volume ratio, and an ORR-favored Pt{111} facet, all of which have been demonstrated to be promoting factors for ORR. With a 10 times higher specific activity and 7 times higher mass activity, this catalyst shows more extraordinary ORR activity than the commercial Pt/C. The ORR activity of icosahedral Pt-enriched nanocages outperforms the cubic and octahedral nanocages reported in the literature, demonstrating the superiority of the icosahedral nanocage structure.

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.

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.

Amorphous nickel boride membrane on a platinum–nickel alloy surface for enhanced oxygen reduction reaction

The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum–nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum–nickel catalyst, and this composite catalyst composed of crystalline platinum–nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.

Li2FeSiO4 nanorods bonded with graphene for high performance batteries

We synthesized a novel 2D hybrid material composed of Li2FeSiO4 nanorods (LFSNRs) anchored on graphene. Such a chemically bonded interface leads to electron coupling at the interface between the nano-LFS and graphene, creating effective charge transport for LFSNR@graphene hybrid cathodes. Used as a cathode material, it possesses a high capacity (300 mA h g−1 at 1.5–4.8 V), high charging–discharging rate (134 mA h g−1 @ 12 C) and long-life performance (maintaining 95% capacity over 240 cycles), which is mainly attributed to the effective depolarization introduced by the synergistic effects of LFSNRs bonded with graphene, which improves the electrochemical activity of the LFSNRs. Thus, a hybrid cathode modified with an interfacial chemical structure with nanoparticles bonded with an electrical conduction network such as graphene or CNTs can significantly enhance the electrochemical performance, and this novel type of material is very promising for commercial applications that require high energy, a long operating life, and excellent abuse tolerance, such as electric vehicles.

Nanocarbon-intercalated and Fe–N-codoped graphene as a highly active noble-metal-free bifunctional electrocatalyst for oxygen reduction and evolution

We report a rationally designed electrocatalyst with high activity for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) based on a nanocarbon-intercalated graphene (CIG) material doped with nitrogen (N) and iron (Fe) (Fe–N-CIG). This easily made novel 3D Fe–N-CIG catalyst exhibits a surprisingly high ORR and OER activity and stability, making it a new noble-metal-free bifunctional catalyst for future applications in regenerative energy conversion systems.

Nano Conductive Ceramic Wedged Graphene Composites as Highly Efficient Metal Supports for Oxygen Reduction

A novel conductive ceramic/graphene nanocomposite is prepared to prohibit the re-stacking of reduced graphene oxide (RGO) by wedging zirconium diboride (ZrB2) nanoparticles (NPs) into multiple layer nanosheets using a simple solvothermal method. Surprisingly, the RGO/ZrB2 nanocomposite supported Pt NPs shows very excellent catalytic activity. Its electrochemical surface area (ECSA) is up to 148 m2g−1 (very approaches the geometry surface area of 155 m2g−1), much greater than that of the previous report (usually less than 100 m2g−1). The mass activity is as high as 16.8 A/g−1, which is almost 2 times and 5 times that of Pt/RGO (8.6 A/g−1) and Pt/C (3.2 A/g−1), respectively, as benchmarks. Moreover, after 4000 cycles the catalyst shows only 61% of ECSA loss, meaning a predominantly electrochemical stability. The remarkably improved electrochemical properties with much high Pt utilization of the new catalyst show a promising application in low temperature fuel cells and broader fields.