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A scalable and simple process was developed for the preparation of Fe 3 O 4 nanoparticles embedded in carbon using nontoxic and affordable materials. The resulting composite showed a high reversible capacity of 702 mA h g À1 as anode material in a Li-ion battery after 50 cycles.Li-ion batteries are considered as one of the best technologies for reversible energy storage and can play in the future a major role as energy vector in transportation. 1-3 For this reason there is a continuous interest in improving the efficiency and developing more durable Li-ion batteries. One of the major research interests in Li-ion batteries has been the nature of the anode material.4,5 Graphite has been widely employed for anode preparation but has as major limitation its low gravimetric capacity (372 mA h g À1 ). Therefore there is still a need for investigating alternative materials that can eventually overcome the limited capacity of graphite.In this context transition metal oxides have received considerable attention since they can exhibit about three times higher capacity than graphite.6-8 This higher capacity is due to the different way in which lithium is incorporated into the anode. Thus, while in the case of graphite lithium becomes incorporated into the interlayer space (lithium intercalation), in the case of metal oxides it is accepted that a different mechanism denoted as ''conversion reaction'' takes place. 9This conversion reaction consists in the storage of lithium as lithium oxide while the transition metal oxides form some metal domains. In this regard, one of the metal oxides that has been preferred in these studies is magnetite (Fe 3 O 4 ) due to the lack of toxicity, availability and low cost of this iron oxide.10-13 Eqn (1) summarizes the electrochemical reaction taking place between Fe 3 O 4 and Li at the anode:This conversion process exhibits a theoretical capacity of 924 mA h g À1. While the proof of principle of this Fe 3 O 4 conversion has been already demonstrated there are still some practical problems that have to be solved before the system can be implemented at the commercial level. In particular, one of the major concerns in this anodic process is the large structural changes that occur during cycling which lead to remarkable variations in the volume and crystal structure that eventually produce a rapid decrease in the energy capacity. 9The two methodologies that have been reported to tackle with the durability and stability of the Fe 3 O 4 films at the anode are complementary and are based on the use of nanoparticles (NPs) with small dimensions and large external surface area which facilitates reversible crystal changes and also the use of hybrid metal oxide-carbon composites.14-16 Carbon in various forms improves the mechanical flexibility of the active Fe 3 O 4 and at the same time ensures the electrical conductivity and reduces the resistance of the metal oxide.There are several ways to form the Fe 3 O 4 and carbon composites. One of these ways consists in the coating of the iron oxide NP with a...

The right dope: Phosphorus‐doped graphene was obtained by the pyrolysis of natural alginate that contained H2PO4− at 900 °C. This material catalyzes the generation of H2 from a water/methanol mixture upon irradiation with UV or visible light. An increase in the amount of H2PO4− leads to a higher photocatalytic activity.

Dye-sensitized graphene oxide is able to generate hydrogen from water/methanol mixtures (80:20) by using visible or solar light. The most efficient photocatalyst tested contained a tris(2,2-bipyridyl) ruthenium(II) complex incorporated in the interlayer spaces of a few layers of graphene oxide with a moderate degree of oxidation. The graphene oxide-based photocatalyst does not contain noble metals and we have determined that it is two orders of magnitude more active than catalysts based on conventional titania.