Lepidocrocite-Type Layered Titanate Nanoparticles as Photocatalysts for H₂ Production

Abstract

The preparation temperature of lepidocrocite-type layered potassium lithium titanate with the formula K0.8Ti1.73Li0.27O4 was optimized for photocatalytic H2 production. K0.8Ti1.73Li0.27O4 was prepared by solid-state reactions at varied temperatures (600–1000 °C) and subsequently treated with dilute HCl to obtain its protonated form. Depending on the preparation temperature, the particle size and crystallinity of K0.8Ti1.73Li0.27O4 varied, and the photocatalytic activity of the protonated forms of K0.8Ti1.73Li0.27O4 for H2 production from aqueous methanol solution was correlated with the preparation temperature. K0.8Ti1.73Li0.27O4 nanoparticles prepared at 700 °C with a particle size estimated to be within the range of ca. 100–300 nm gave the largest amount of H2, equivalent up to 42 times higher than that given by K0.8Ti1.73Li0.27O4 prepared at commonly reported temperatures (≥800 °C). This finding reinforces the importance of preparation temperature to full utilization of the capabilities of nanomaterials derived from ceramic processes.

Altering the Alkaline Metal Ions in Lepidocrocite-Type Layered Titanate for Sodium-Ion Batteries

“…In the high-resolution XPS spectrum of Ti 2p (Figure c), a pair of peaks centered at 458.4, 458.2, 458.3, and 458.4 eV for 2p 3/2 and 464.1, 463.8, 464.0, and 464.2 eV for 2p 1/2 are observed for Li-ILT, Na-ILT, K-ILT, and Cs-ILT, respectively. The positions of these peaks are very close to each other, and the peaks can be assigned to Ti 4+ in bulk form. − Besides these, two additional peaks centered at ∼459.1 eV for 2p 3/2 and ∼465.5 eV for 2p 1/2 are present in all LTs, and these peaks are identical to those of Ti 4+ in titanate nanosheets, suggesting the presence of a small amount of nanosized titanate. The O 1s peak in Figure d was fitted with three peaks for Li-ILT, K-ILT, and Cs-ILT and with four peaks for Na-ILT.…”

“…For Li-ILT, these peaks are at 529.8, 530.5, and 531.6 eV; for Na-ILT, at 529.6, 530.3, 531.7, and 534.5 eV; for K-ILT, at 529.7, 530.3, and 532.0 eV; and for Cs-ILT, at 530.0, 530.7, and 532.2 eV. From the low-energy side, these three O 1s peaks can be assigned to the 2-coordinated oxygen, the 4-coordinated oxygen, and water. , Meanwhile the fourth peak, at 534.5 eV in Na-ILT, is assigned to water in bilayer form. The formation of a bilayer hydrate in Na-ILT can also be evidenced by the XRD data of Na-ILT (Figure a).…”

“…From the low-energy side, these three O 1s peaks can be assigned to the 2-coordinated oxygen, the 4coordinated oxygen, and water. 40,41 Meanwhile the fourth peak, at 534.5 eV in Na-ILT, is assigned to water in bilayer form. The formation of a bilayer hydrate in Na-ILT can also be evidenced by the XRD data of Na-ILT (Figure 1a).…”

Efficient p–n Heterojunction Photocatalyst Composed of Bismuth Oxyiodide and Layered Titanate

“…If compared with smectite clays, which are normally photocatalytic inactive, CsTLO is a more interesting counterpart of BiOXs for photocatalytic applications. Here, in order to elucidate the origin of the present size-controlled synthesis of BiOI at room temperature, we prepared CsTLO with a smaller particle size by lowering the synthetic temperature upon the solid-state reaction. , The XRD pattern of CsTLO-small (Figure S6a) was indexed to CsTLO. The absorption edge of CsTLO-small (Figure S6b) slightly shifted from that of CsTLO to a shorter wavelength region.…”

“…Here, in order to elucidate the origin of the present sizecontrolled synthesis of BiOI at room temperature, we prepared CsTLO with a smaller particle size by lowering the synthetic temperature upon the solid-state reaction. 48,49 The XRD pattern of CsTLO-small (Figure S6a) was indexed to CsTLO.…”