Scanning X-ray Photoelectron Microscopy Research Articles

Effect of Carbon Nanotubes on the Na+ Intercalation Capacity of Binder Free Mn2V2O7-CNTs Electrode: A Structural Investigation

Improvements in sodium intercalation in sodium cathodes have been debated in recent years. In the present work, we delineate the significant effect of the carbon nanotubes (CNTs) and their weight percent in the intercalation capacity of the binder-free manganese vanadium oxide (MVO)-CNTs composite electrodes. The performance modification of the electrode is discussed taking into account the cathode electrolyte interphase (CEI) layer under optimal performance. We observe an intermittent distribution of the chemical phases on the CEI, formed on these electrodes after several cycles. The bulk and superficial structure of pristine and Na+ cycled electrodes were identified via micro-Raman scattering and Scanning X-ray Photoelectron Microscopy. We show that the inhomogeneous CEI layer distribution strongly depends on the CNTs weight percentage ratio in an electrode nano-composite. The capacity fading of MVO-CNTs appears to be associated with the dissolution of the Mn2O3 phase, leading to electrode deterioration. This effect is particularly observed in electrodes with low weight percentage of the CNTs in which the tubular topology of the CNTs are distorted due to the MVO decoration. These results can deepen the understanding of the CNTs role on the intercalation mechanism and capacity of the electrode, where there are variations in the mass ratio of CNTs and the active material.

In Aqua Electrochemistry Probed by XPEEM: Experimental Setup, Examples, and Challenges

Recent developments in environmental and liquid cells equipped with electron transparent graphene windows have enabled traditional surface science spectromicroscopy tools, such as scanning X-ray photoelectron microscopy, X-ray photoemission electron microscopy (XPEEM), and scanning electron microscopy to be applied for studying solid–liquid and liquid–gas interfaces. Here, we focus on the experimental implementation of XPEEM to probe electrified graphene–liquid interfaces using electrolyte-filled microchannel arrays as a new sample platform. We demonstrate the important methodological advantage of these multi-sample arrays: they combine the wide field of view hyperspectral imaging capabilities from XPEEM with the use of powerful data mining algorithms to reveal spectroscopic and temporal behaviors at the level of the individual microsample or the entire array ensemble.

Nitrogen implantation of suspended graphene flakes: Annealing effects and selectivity of sp2 nitrogen species

Nitrogen inclusion in both chemical vapour deposition and exfoliated few-layer graphene flakes was performed by nitrogen ion implantation in ultra-high vacuum. Inclusion of up to ∼20 at.% nitrogen can be reached through this clean technique with absence of oxygen species in the final product, while maintaining a largely sp2-carbon network. The nitrogen inclusion was observed by scanning X-ray photoelectron microscopy (SPEM) with energy resolution of 0.2eV and spatial resolution of 10nm. SPEM can be used to follow the evolution of nitrogen species: pyridinic, graphitic, and pyrrolic, at different doping stages and annealing temperatures. Variations in the ratio between sp2 nitrogen species was observed for increasing treatment time; annealing results in quenching of the sp3 component, suggesting the graphitic nitrogen as the most thermal stable species. The occurrence of graphitic species together with the absence of pyrrolic is indicative of N-incorporation into a hexagonal graphene-based lattice. Ion irradiation followed by annealing performed in a controlled way is a promising strategy to fine control the nature of the nitrogen species grafted to the graphene while focusing on selected applications.

X-ray probe microanalyses and scanning x-ray microscopies

The focusing and scanning of X-ray photon beam is a difficult operation. Thus in order to obtain data concerning the elemental composition of a specimen, the analytical techniques based on incident X-ray photons have generally a poor degree of lateral localization. The aim of the present paper is to show how it is possible to develop microanalytical techniques based on X-ray excitation of inner shell electrons like X-ray photoelectron spectroscopy (XPS or ESCA)and X-ray induced Auger electron spectroscopy (XAES)for surface analysis; X-ray fluorescence spectroscopy (XRF)for bulk analysis. The same experimental arrangement is also applied to develop the corresponding scanning microscopies: Scanning X-ray Photoelectron Microscopy(SXPM), Scanning X-ray induced Auger Microscopy(SXAM)and Scanning X-ray radiography(SXR). The experimental set-up and obtained results will be presented; further improvements and comparisons with other technical solutions will be discussed.

X-ray probe microanalyses and scanning x-ray microscopies

The analytical techniques based on excitation of inner-shell electrons by an incident X-ray photon beam suffer generally from their poor degree of lateral localization. Nevertheless it is possible to perform the microanalysis of a sample in the forms of a thin film by: (i) X-ray photoelectron spectroscopy (XPS or ESCA) and X-ray-induced Auger electron spectroscopy (XAES) for surface analysis; (ii) X-ray absorption spectroscopy (XAS) and X-ray microfluorescence spectroscopy (XMS) for bulk analysis. The corresponding images can also be obtained in the scanning mode: scanning X-ray photoelectron microscopy (SXPM), scanning X-ray-induced Auger electron microscopy (SXAEM) and scanning X-ray microradiography (SXM). The experimental arrangement and the results obtained are described here, together with further improvements and comparisons with other technical solutions.