Functional Species Encapsulated in Nitrogen-Doped Porous Carbon as a Highly Efficient Catalyst for the Oxygen Reduction Reaction.

The scarcity, high cost, and poor stability of precious metal-based electrocatalysts have stimulated the development of novel non-precious metal catalysts for the oxygen reduction reaction (ORR) for use in fuel cells and metal-air batteries. Here, we fabricated in situ a hybrid material (Co-W-C/N) with functional species (tungsten carbide and cobalt nanoparticles) encapsulated in an N-doped porous carbon framework, through a facile multi-constituent co-assembly method combined with subsequent annealing treatment. The unique structure favors the anchoring active nanoparticles and facilitates mass transfer steps. The homogenously distributed carbide nanoparticles and adjacent Co-N-C sites lead to the electrocatalytic synergism for the ORR. The existence of Co and W can promote the graphitization of the carbon matrix. Benefiting from its structural and material superiority, the Co-W-C/N electrocatalyst exhibits excellent electrocatalytic activity (with a half-wave potential of 0.774 V vs. reversible hydrogen electrode (RHE)), high stability (96.3 % of the initial current remaining after 9000 s of continuous operation), and good immunity against methanol in alkaline media.

Hollow Mesoporous Fe2O3 Nanospindles/CNTs Composite: An Efficient Catalyst for High-Performance Li-O2 Batteries.

The design of mesoporous or hollow transition metal oxide/carbon hybrid catalysts is very important for rechargeable Li-O2 batteries. Here, spindle-like Fe2O3 with hollow mesoporous structure on CNTs backbones (Fe2O3-HMNS@CNT) are prepared by a facile hydrolysis process combined with low temperature calcination. Within this hybrid structure, the hollow interior and mesoporous shell of the Fe2O3 nanospindles provide high specific surface area and abundant catalytical active sites, which is also beneficial to facilitating the electrolyte infiltration and oxygen diffusion. Furthermore, the crisscrossed CNTs form a three-dimensional (3D) conductive network to accelerate and stabilize the electron transport, which leads to the decreasing internal resistance of electrode. As a cathodic catalyst for Li-O2 batteries, the Fe2O3-HMNS@CNT composite exhibits high specific capacity and excellent cycling stability (more than 100 cycles).