Nanostructured TiO2 Arrays for Energy Storage

Abstract

Because of their extensive specific surface area, excellent charge transfer rate, superior chemical stability, low cost, and Earth abundance, nanostructured titanium dioxide (TiO₂) arrays have been thoroughly explored during the past few decades. The synthesis methods for TiO₂ nanoarrays, which mainly include hydrothermal/solvothermal processes, vapor-based approaches, templated growth, and top-down fabrication techniques, are summarized, and the mechanisms are also discussed. In order to improve their electrochemical performance, several attempts have been conducted to produce TiO₂ nanoarrays with morphologies and sizes that show tremendous promise for energy storage. This paper provides an overview of current developments in the research of TiO₂ nanostructured arrays. Initially, the morphological engineering of TiO₂ materials is discussed, with an emphasis on the various synthetic techniques and associated chemical and physical characteristics. We then give a brief overview of the most recent uses of TiO₂ nanoarrays in the manufacture of batteries and supercapacitors. This paper also highlights the emerging tendencies and difficulties of TiO₂ nanoarrays in different applications.

Keywords: TiO2; batteries; energy storage; nanoarrays; supercapacitors.

Figure 1

The different dimensional morphology of nanostructured TiO₂ arrays.

Figure 2

(a,b) The cross-sectional views of TiO₂ nanowires at different magnifications. Reprinted with permission from [31], Copyright 2008 IOP Publishing. (c,d) The cross-sectional views of electrospun TiO₂ nanowires. Reprinted with permission from [39], Copyright 2013 Elsevier. (e–h) FESEM images of anatase TiO₂ nanowires on different substrates (The insets correspond low-magnification images) and (i) rutile TiO₂ nanorod arrays. Reprinted with permission from [23], Copyright 2014 The Royal Society of Chemistry.

Figure 3

(a,b) The top and cross-sectional FESEM images of rutile TiO₂ nanorod arrays film grown on FTO substrate. Reprinted with permission from [27], Copyright 2009 American Chemical Society. (c–e) FESEM image and (f) TEM image of rutile TiO₂ nanorod arrays film grown on Ti substrate. Reproduced with permission from [46], Copyright 2011 Elsevier.

Figure 4

(a,b) The SEM of TiO₂ nanotubes in different electrolyte. Reprinted with permission from [68], Copyright 2012 American Chemical Society. (c) SEM image of TiO₂ 3D nanoforest. (d) SEM image, (e) TEM images of hollow nanostructures in the cap and nanowire regions are shown in (iii) and (iv) respectively, (f) SEM images after 600 depositions, (g) SEM image and (h,i) Low- and high-(ii) magnification TEM images of titanium dioxide nanowires using ZnO nanowires as a template. Reprinted with permission from [81], Copyright 2014 American Chemical Society.

Figure 5

Schematic illustration, SEM images, and TEM images of (a–d) random, (e–h) sealed, and (i–l) unsealed TiO₂ nanotubes. Reproduced with permission from [82], Copyright 2012 American Chemical Society.

Figure 6

Top view (a–c) cross-sectional view SEM images for layered TiO₂ nanosheet arrays. Reprinted with permission from [94], Copyright 2015 Elsevier. (d) Overall strategy and SEM images toward 2D TiO₂ nanosheet arrays. (e) Schematic illustration for the formation of nanosheet arrays. Reprinted with permission from [95], Copyright 2011 American Chemical Society.

Figure 7

SEM images of (a,b) TiO₂ nanoarrays film, (c,d) the core-shell branched nanowire arrays and (e,f) the core-shell branched nanobelt arrays. Reprinted with permission from [96], Copyright 2015 Springer Nature.

Figure 8

(a,b) SEM images of TiO₂ nanobelts. Reprinted with permission from [97], Copyright 2013 The Royal Society of Chemistry. (c,d) SEM images of the TiO₂@MnO₂ nanobelt arrays. Reprinted with permission from [98], Copyright 2013 The Royal Society of Chemistry.

Figure 9

(a–f) SEM images of nanotrees. Reprinted with permission from [104], Copyright 2009 American Chemical Society. (g) FESEM image and (h) TEM image of the F decorated TiO₂ nanowires. Reprinted with permission from [103], Copyright 2023 Elsevier.

Figure 10

Schematic illustrations and SEM/TEM images of (a–c) nanosheet branches and (d–f) nanosheet and nanorod branches. Reprinted with permission from [109], Copyright 2014 Springer Nature. Schematic illustration of the H-TiO₂ NRAs photoanode: (g) TiO₂ NRAs, (h) branched ZnO/TiO₂ NRAs, and (i) H-TiO₂ NRAs. Reprinted with permission from [25], Copyright 2015 The Royal Society of Chemistry.

Figure 11

(a,b) FESEM images and (c) TEM images of hierarchical TiO₂ nanotube arrays. Reprinted with permission from [112], Copyright 2014 Wiley. (d) FESEM images and (e) TEM images of TiN and TiN/TiO₂ nanowires. Reprinted with permission from [113], Copyright 2017 Elsevier.

Figure 12

(a) Schematic diagram and (b,c) FESEM images of TiO₂ nanoflower arrays. Reprinted with permission from [114], Copyright 2022 The Royal Society of Chemistry. (d) FESEM image and (e,f) TEM image of 3D TiO₂ nanoarrays. (g,h) Characterizations of the change in the lattice parameters and its generation mechanism. Reprinted with permission from [115], Copyright 2021 American Chemical Society.

Figure 13

(a) Diagram, (b) TEM image, (c,d) EDS mapping images, (e) HAADF-STEM image, and (f) FESEM image (the inset shows the cross-section) of TiN nanotrees. Reprinted with permission from [117], Copyright 2019 The Royal Society of Chemistry.

Figure 14

Electrochemical performances of TiO₂ nanotrees. (a) The CV curves. (b) The cycling performance. (c) Cycling stability at 1.0 mA cm⁻². (d) The rate capability. (e) Comparison of the rate capability of TiO₂ nanotrees and other materials [46,154,153,154,155,156]. Reprinted with permission from [154], Copyright 2016 The Royal Society of Chemistry.

Figure 15

Electronical performance of the TiN/TiO₂ Nanowire Arrays. (a) The CV curves. (b) The GCD profiles. (c) Determination of b value using the relationship between peak current and scan rate. (d) Voltage offset (ΔE_p) of TiN/TiO₂ nanowire arrays. (e) Contribution ratio of the capacitive and diffusion-controlled capacities. (f) The rate capability of TiN/TiO₂ nanowire arrays [113,155,156,171]. (g) Cycling performance. Reprinted with permission from [113], Copyright 2017 Elsevier.

Figure 16

The electrochemical test of F-decorated TiO₂ nanoarrays. (a) The CV curves. (b) Determination of the b value using the relationship between peak current and scan rate. (c) The GCD profiles and (d) areal capacitances of different samples. (e) The GCD profiles. (f) Comparing the areal capacitances with other TiO₂ materials [105,218,219,220,223,225,226,228]. (g) The cycling stability. Reprinted with permission from [105], Copyright 2023 Elsevier.

Figure 17

The electrochemical performances of anatase TiO₂ nanoarrays. (a) The CV curves. (b) The GCD profiles. (c) The specific capacities of the half-cell. (d) Schematic diagram of the full cell. (e) The GCD profiles of the full cell. (f) Ragone plots of batteries [110,253,255,256,257,258]. Reprinted with permission from [110], Copyright 2021 American Chemical Society.