X-ray photoelectron spectroscopy of high-throughput mechanically exfoliated van der Waals materials.

X-ray photoelectron spectroscopy (XPS) is a widely used and easy accessible characterisation technique for investigating the chemical composition of materials. However, investigating the composition of van der Waals (vdW) flakes by XPS is challenging due to the typical spot size of XPS setups compared to the dimensions of the flakes, which are usually one thousand times smaller than the spot size. In this work, we demonstrate the feasibility of quantitative elemental analysis of vdW materials by using high-throughput mechanical exfoliations, which favour the coverage of arbitrary substrates with flakes of areas of the order of the cm using minimal quantities of materials (about 10 μg).

Protecting TiS Photoanodes for Water Splitting in Alkaline Media by TiO Coatings.

Titanium trisulfide (TiS) nanoribbons, when coated with titanium dioxide (TiO), can be used for water splitting in the KOH electrolyte. TiO shells can be prepared through thermal annealing to regulate the response of TiS/TiO heterostructures by controlling the oxidation time and growth atmosphere. The thickness and structure of the TiO layers significantly influence the photoelectrocatalytic properties of the TiS/TiO photoanodes, with amorphous layers showing better performance than crystalline ones.

Potassium doping of vertically aligned multi-walled carbon nanotubes.

Alkali metal doping of multi-walled carbon nanotubes is of great interest, both fundamentally to explore the effect of dopants on quasi-one-dimensional electrical systems and for energy applications such as alkali metal storage. We present an investigation with complementary photoemission and Raman spectroscopies, fully carried out in an ultra-high vacuum, to unveil the electronic and vibrational response of a forest of highly aligned multi-walled carbon nanotubes by in situ potassium doping. The charge donation by the alkali adatoms induces a plasmon mode, and the density of states undergoes an energy shift consistent with electron donation and band filling of the multi-walled carbon nanotube band structure.

Spectromicroscopy Study of Induced Defects in Ion-Bombarded Highly Aligned Carbon Nanotubes.

Highly aligned multi-wall carbon nanotubes were investigated with scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after bombardment performed using noble gas ions of different masses (argon, neon and helium), in an ultra-high-vacuum (UHV) environment. Ion irradiation leads to change in morphology, deformation of the carbon (C) honeycomb lattice and different structural defects in multi-wall carbon nanotubes. One of the major effects is the production of bond distortions, as determined by micro-Raman and micro-X-ray photoelectron spectroscopy.

Borocarbonitride Layers on Titanium Dioxide Nanoribbons for Efficient Photoelectrocatalytic Water Splitting.

Heterostructures formed by ultrathin borocarbonitride (BCN) layers grown on TiO nanoribbons were investigated as photoanodes for photoelectrochemical water splitting. TiO nanoribbons were obtained by thermal oxidation of TiS samples. Then, BCN layers were successfully grown by plasma enhanced chemical vapour deposition.