Yujiang Song

Reduced TiO2 rutile nanorods with well-defined facets and their visible-light photocatalytic activity

Stable reduced TiO2 rutile nanorods with well-defined facets were prepared by a solvothermal route in the presence of Zn powder. The oxygen vacancy in the TiO2 nanorods, which can be tuned by the amount of Zn, results in a narrow band gap and visible-light photocatalytic activity.

A high-performance electrocatalyst for oxygen reduction based on reduced graphene oxide modified with oxide nanoparticles, nitrogen dopants, and possible metal-N-C sites

Non-noble metal (NNM) electrocatalysts with performances comparable with or superior to Pt are highly desirable for fuel cells and metal-air batteries, but remain rare. Herein, we report a new NNM electrocatalyst derived from reduced graphene oxide (rGO), dual nitrogen-containing ligands, and iron and cobalt salts. Remarkably, the onset potential and half-wave potential (E1/2) of the obtained electrocatalyst shifts 5 and −23 mV, respectively, relative to commercial Pt/C at a standard loading of 20 μgpt cm−2 toward an oxygen reduction reaction (ORR) in alkaline solutions. Additionally, the electrocatalyst is much better than the Pt/C in terms of durability and tolerance to methanol.

Light-controlled synthesis of uniform platinum nanodendrites with markedly enhanced electrocatalytic activity

AbstractWe report a fast in situ seeding approach based on zinc(II) porphyrin (ZnP) under white light irradiation, leading to uniform spherical platinum nanodendrites with tunable sizes. The platinum nanodendrites exhibit significantly improved electrocatalytic activities toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) compared with commercial platinum black.n

Controlled synthesis of high metal-loading, Pt-based electrocatalysts with enhanced activity and durability toward oxygen reduction reaction

High metal-loading Pt/C electrocatalysts are much sought after for the fabrication of thin-layered membrane electrode assemblies (MEA) suitable for mass transport and balance control of water and heat. However, such electrocatalysts are still limited to commercial Pt/C, comprised of carbon-supported, 2–5 nm Pt particles without size and size uniformity control, causing poor activity and durability toward oxygen reduction reaction (ORR). Herein, we report the controlled synthesis of 59.9 wt% Pt/C by using metallic ion-containing reversed micelles adsorbed on carbon. Combined with a simple surfactant removal method of washing with water, this unique confining approach enables easy control over the size and size uniformity of the resultant Pt/C, leading to significantly improved activity and durability for ORR compared with commercial 60 wt% Pt/C. The ORR activity enhancement arises from a smaller average size of Pt nanoparticles in combination with a narrower size distribution, with more Pt nanoparticles falling in an optimal size range of 2–4 nm with the highest ORR activity. The narrower size distribution of our Pt/C also makes the Pt nanoparticles resistant to the dissolution–re-deposition Ostwald ripening process, in which small Pt nanoparticles gradually shrink until they disappear, while large ones become bigger and bigger.

One-step synthesis of carbon-supported foam-like platinum with enhanced activity and durability

Carbon black nanoparticles localized in-between liposomal bi-layers provide a unique reaction environment that permits one-step synthesis of carbon-supported foam-like platinum (Pt foam/C) in aqueous solution under ambient conditions. The obtained Pt foam/C was readily purified by simple washing with water and chloroform at room temperature. Unlike commercial Pt/C composed of quasi-spherical nanoparticles, Pt foam/C consists of convoluted dendritic nanosheets. Interestingly, Pt foam/C demonstrated both improved durability and activity toward oxygen reduction reaction (ORR). The improved durability is because of the formation of metastable nano-holes among dendritic branches of Pt foam/C under ripening, preserving the surface area. The activity enhancement of Pt foam/C can be attributed to predominantly exposed Pt {1,1,0} planes that possess the highest ORR activity among all low-indexed Pt crystalline planes. Nano-scale Pt primarily enclosed by {1,1,0} planes has not been reported previously.

Graphene supported foam-like platinum electrocatalyst for oxygen reduction reaction

Graphene supported platinum seeds localized in between liposomal bi-layer provide a unique supporting-seeding-templating tri-functional reaction environment that permits the synthesis of graphene supported foam-like platinum (Pt foam/G). Pt foam consists of 2–3 nm thick dendritic nanosheets. In order to prevent graphene from stacking together, carbon black particles were inserted among graphene sheets. Interestingly, Pt foam/G showed a much higher oxygen reduction reaction (ORR) activity compared with commercial Pt/C composed of semi-spherical nanoparticles supported on carbon. Moreover, accelerated durability test demonstrated that the Pt foam/G exhibited a better stability than commercial Pt/C.

Synthesis, Purification, and Electrocatalytic Activity of Platinum Nanocatalyst with Globular Dendritic Structure: Synthesis, Purification, and Electrocatalytic Activity of Platinum Nanocatalyst with Globular Dendritic Structure

A new Pt nanocatalyst was synthesized by chemical reduction of K2PtCl4 by ascorbic acid in the presence of a non-ionic surfactant Brij-35 (CH3(CH2)(10)CH2(OCH2CH2)(23)OH) in aqueous solution at room temperature. The obtained Pt nanocatalyst was characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction, thermogravimetry (TG), and cyclic voltammetry (CV). The uniform Pt nanocatalyst possesses a globular dendritic morphology with a mean diameter of 36.9 nm. The branches of the globular dendrites are 2-4 nm in diameter and 4-6 nm in length. A simple purification method with multiple water washing was developed to remove Brij-35 and other by-products from the surface of Pt nanocatalyst. TG, EDX, and CV results show that the surface of Pt nanocatalyst after purification is as clean as that of commercial Pt black (fuel cell grade, 99.9%). Compared with commercial Pt black, Pt nanocatalyst demonstrates a higher electrochemical active surface area and significantly improved electrocatalytic activity to oxygen reduction and methanol oxidation.