Exploration of nanowire- and nanotube-based electrocatalysts for oxygen reduction and oxygen evolution reaction

Abstract Electrocatalysts for oxygen reduction and/or evolution are key components for proton-exchange membrane fuel cells (PEMFCs) and water electrolysis. However, the slow kinetics of oxygen reduction and/or evolution reactions largely hampers the efficiencies of PEMFCs and water electrolysis. Highly efficient electrocatalysts for oxygen reduction and evolution reactions must meet three requirements: (i) rapid transport of electrons, ions, and products of the reaction; (ii) sufficient catalysts/reactants contact area; and (iii) good intrinsic activity. Nanostructuration of electrocatalysts provides an effective approach to overcome the slow kinetics because nanostructured electrocatalysts with rational design can not only provide sufficient active sites but also promote intrinsic activity of electrocatalysts as well as possess the ability of rapid transport of electrons, ions, and products of the reaction. Especially, electrocatalysts in the form of one-dimensional nanostructures (1D-Nano) such as nanowires (NWs) and nanotubes (NTs) have shown significant advantages, such as high surface area, rapid electron and mass transfer, low vulnerability to dissolution, Ostwald ripening, and aggregation, for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this review, we summarize different strategies for fabricating 1D nanostructure-based electrocatalysts (1D-NanoECs), which are categorized into template-free and template-assisted strategies, and emphasis has been placed on anodic aluminum oxide template–assisted strategies. Then, recent advances of 1D-NanoECs for ORR and OER applications are summarized. Finally, future challenges and opportunities about 1D-NanoECs are discussed.