We used anionic sulfate surfactants to assist the stabilization of graphene in aqueous solutions and facilitate the self-assembly of in situ grown nanocrystalline TiO2, rutile and anatase, with graphene. These nanostructured TiO2-graphene hybrid materials were used for investigation of Li-ion insertion properties. The hybrid materials showed significantly enhanced Li-ion insertion/extraction in TiO2. The specific capacity was more than doubled at high charge rates, as compared with the pure TiO2 phase. The improved capacity at high charge−discharge rate may be attributed to increased electrode conductivity in the presence of a percolated graphene network embedded into the metal oxide electrodes.

N anocomposites have attracted wide attention because of their potential to combine desirable properties of different nanoscale building blocks to improve mechanical, optical, electronic , or magnetic properties. 16 Most traditional synthesis approaches of nanocom-posites rely on mechanical or chemical mixing and produce a random distribution of the constitutive phases. To address these problems, several groups recently investigated layer-by-layer deposition and other techniques to prepare layered nanocom-posites with ceramics, clays, and graphite oxide nanoplatelets, 79 but these methods are lacking in nanoscale spatial precision and are time-consuming and difficult for bulk-materials synthesis. On the other hand, biological systems abound with nanocom-posites that possess well-controlled archi-tectures based on multiple scale and multi-functional building blocks. 10 One powerful approach to achieve similar control is to use amphiphilic polymer or surfactant to direct the self-assembly of nanostructured metal oxides, semiconductors, and polymer materials. 1115 There has been a growing interest in incorporating functional components , such as functional groups, polymers, and nanoparticles, into the self-assembled nanostructures, but success has been limited to two-phase organic/inorganic hybrid materials, nanoparticles, or polymer-based nanocomposites. 4,5,16,17 Recently, a range of nanoscale building blocks, including carbon nanotubes 1821 and graphene, 2224 have gained prominence. Graphene and graphene stacks (mul-tilayer graphene), potentially low cost alternative materials to single-wall or multiwall carbon nanotubes, have unique electronic conductivity and mechanical properties. 2527 Graphene-based nanocom-posites with polymer, metal, or metal oxides have also shown unique mechanical, electronic , and electrochemical properties. 23,2835 We focus on the nano-composites made of metal oxides (i.e., SnO 2 , NiO, MnO 2 , and SiO 2) that could have important applications for electrochemical energy storage. 36,37 The low conductivity and poor stability of such materials usually necessitate adding conductive phases to enhance electron transport and electrical contact of the active materials in the electrode of a Li-ion battery. In most of these studies, the approach used to prepare the composite materials has been mechanical mixing of metal oxides with conductive materials such as amorphous carbon, carbon nano-tubes, and graphene. 31,38 In spite of these studies, a well-controlled architecture of the conductive material and metal oxide is difficult to achieve because of improper ABSTRACT Surfactant or polymer directed self-assembly has been widely investigated to prepare nanostructured metal oxides, semiconductors, and polymers, but this approach is mostly limited to two-phase materials, organic/inorganic hybrids, and nanoparticle or polymer-based nanocomposites. Self-assembled nanostructures from more complex, multiscale, and multiphase building blocks have been investigated with limited success. Here, we demonstr...

Carbon-supported precious metal catalysts are widely used in heterogeneous catalysis and electrocatalysis, and enhancement of catalyst dispersion and stability by controlling the interfacial structure is highly desired. Here we report a new method to deposit metal oxides and metal nanoparticles on graphene and form stable metal-metal oxide-graphene triple junctions for electrocatalysis applications. We first synthesize indium tin oxide (ITO) nanocrystals directly on functionalized graphene sheets, forming an ITO-graphene hybrid. Platinum nanoparticles are then deposited, forming a unique triple-junction structure (Pt-ITO-graphene). Our experimental work and periodic density functional theory (DFT) calculations show that the supported Pt nanoparticles are more stable at the Pt-ITO-graphene triple junctions. Furthermore, DFT calculations suggest that the defects and functional groups on graphene also play an important role in stabilizing the catalysts. These new catalyst materials were tested for oxygen reduction for potential applications in polymer electrolyte membrane fuel cells, and they exhibited greatly enhanced stability and activity.

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