Multihierarchical electrodes based on titanate nanotubes and zinc oxide nanorods for photoelectrochemical water splitting

Abstract

a Studies involving water splitting to form hydrogen and oxygen have attracted attention because H2is considered the fuel of the future. Photoelectrocatalysts have been widely used for this application, and several metal oxides can be applied as catalysts. Among them, we highlight zinc oxide nanorods (ZnONRs) and titanate nanotubes (TiNTs); however, their individual nanostructures exhibit disadvantages. For example, ZnONR shows rapid recombination of the photogenerated charges, and TiNT gives rise to randomly orientated films; these disadvantages limit their application as photoanodes. In this study, for the first time, we present a new class of multihierarchical electrodes based on TiNT-decorated ZnONR films that exhibited superior results to the individual species. The TiNTs are homogenously dispersed over the surface of the rods without forming agglomerates, giving rise to a heterojunction that exhibits lower recombination rates. It was found that the results are better when the contents of TiNT in the electrode are higher; thus, glycine was successfully used as a bridge to link both of the structures, increasing the amount of TiNT decorating the rods. As a result, the photocurrent generated with these multihierarchical electrodes is higher than that obtained for pure ZnONR electrodes (0.9 mA and 0.45 mA, respectively), and the electrode potentials for O2 evolution is lower than that observed for pure TiNT electrodes (0 V and 0.8 V vs. ERHE, respectively). The IPCE values are also higher for the multihierarchical electrodes.

Tailoring a Zinc Oxide Nanorod Surface by Adding an Earth‐Abundant Cocatalyst for Induced Sunlight Water Oxidation

“…Top‐view SEM images of the electrodes show the hexagonal shape of the ZnO nanorods films (Figure a) with an average diameter of (115±33) nm, which is consistent with previously reported works . SEM images of the 6d‐FeOOH/ZnONR electrode show that the ZnO nanorods are unaffected by the addition of FeOOH nanoparticles (Figure b).…”

“…X‐ray Diffraction (XRD) analysis was performed to check the crystal structure of ZnO and to observe whether there are any changes on modifying the ZnO nanorod surface. Figure illustrates that it is possible to characterize the diffraction pattern of ZnO as wurtzite . The black dot indicates the diffraction peak corresponding to the FTO substrate.…”

“…ZnO nanorods films were vertically grown on the FTO substrate. Both zinc oxide nanorods and FeOOH nanoparticles were synthesized using reported procedures under hydrothermal conditions . In summary, a seed layer of ZnO was produced so as to make the growth of ZnO nanorods possible.…”

Fe2PO5‐Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

“…With rising concern over continuous increase of energy consumption and fossil fuel depletion, searching for a sustainable energy resource is highly urgent to be able to meet our current and future energy demands . Hydrogen has attracted extensive attention and is considered to be an ideal fuel in the future owing to its environmentally friendly profile and high energy density . Among the various techniques used for hydrogen generation, photoelectrochemical water splitting with the help of sunlight has long been thought to be promising since the discovery of TiO 2 as photocatalyst in 1972 by Honda and Fujishima .…”

Multiscale Hierarchical Micro- and Nanostructures: Nanotubes and Micro-Assembly

“…Examples of simultaneous assembly of mictro and nanotubes of TiO2 [1], step by step crafting of titanate nanotubes into TiO2 nanotubes [2] or on the surface of ZnO nanorods [3] are to be considered. The needs and benefits of such multiscale micro-and nanometres hierarchical structures in several technological applications including dye sensitized solar cells, fuel cells and lithium batteries, catalysis will be illustrated in terms of transport, capacity and cost.…”